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Articles de revues sur le sujet "Leader genes"
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Orlando, Bruno, Luca Giacomelli, Massimiliano Ricci, Antonio Barone et Ugo Covani. « Leader genes in osteogenesis : a theoretical study ». Archives of Oral Biology 58, no 1 (janvier 2013) : 42–49. http://dx.doi.org/10.1016/j.archoralbio.2012.07.010.
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Di Spirito, Federica, Paolo Toti, Vincenzo Pilone, Francesco Carinci, Dorina Lauritano et Ludovico Sbordone. « The Association between Periodontitis and Human Colorectal Cancer : Genetic and Pathogenic Linkage ». Life 10, no 9 (18 septembre 2020) : 211. http://dx.doi.org/10.3390/life10090211.
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Periodontitis has been associated with an increased risk of and mortality associated with human colorectal cancer (CRC). Current evidence attributes such an association to the direct and indirect effects of virulence factors belonging to periodontal pathogens, to inflammatory mediators and to genetic factors. The aims of the study were to assess the existence of a genetic linkage between periodontitis and human CRC, to identify genes considered predominant in such a linkage, thus named leader genes, and to determine pathogenic mechanisms related to the products of leader genes. Genes linking periodontitis and CRC were identified and classified in order of predominance, through an experimental investigation, performed via computer simulation, employing the leader gene approach. Pathogenic mechanisms relating to leader genes were determined through cross-search databases. Of the 83 genes linking periodontitis and CRC, 12 were classified as leader genes and were pathogenically implicated in cell cycle regulation and in the immune-inflammatory response. The current results, obtained via computer simulation and requiring further validation, support the existence of a genetic linkage between periodontitis and CRC. Cell cycle dysregulation and the alteration of the immuno-inflammatory response constitute the pathogenic mechanisms related to the products of leader genes.
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Covani, Ugo, Simone Marconcini, Luca Giacomelli, Victor Sivozhelevov, Antonio Barone et Claudio Nicolini. « Bioinformatic Prediction of Leader Genes in Human Periodontitis ». Journal of Periodontology 79, no 10 (octobre 2008) : 1974–83. http://dx.doi.org/10.1902/jop.2008.080062.
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Dossin, Fernando de Macedo, et Sergio Schenkman. « Actively Transcribing RNA Polymerase II Concentrates on Spliced Leader Genes in the Nucleus of Trypanosoma cruzi ». Eukaryotic Cell 4, no 5 (mai 2005) : 960–70. http://dx.doi.org/10.1128/ec.4.5.960-970.2005.
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ABSTRACT RNA polymerase II of trypanosomes, early diverging eukaryotes, transcribes long polycistronic messages, which are not capped but are processed by trans-splicing and polyadenylation to form mature mRNAs. The same RNA polymerase II also transcribes the genes coding for the spliced leader RNA, which are capped, exported to the cytoplasm, processed, and reimported into the nucleus before they are used as splicing donors to form mRNAs from pre-mRNA polycistronic transcripts. As pre-mRNA and spliced leader transcription events appear to be uncoupled, we studied how the RNA polymerase II is distributed in the nucleus of Trypanosoma cruzi. Using specific antibodies to the T. cruzi RNA polymerase II unique carboxy-terminal domain, we demonstrated that large amounts of the enzyme are found concentrated in a domain close to the parasite nucleolus and containing the spliced leader genes. The remaining RNA polymerase II is diffusely distributed in the nucleoplasm. The spliced leader-associated RNA polymerase II localization is dependent on the cell transcriptional state. It disperses when transcription is blocked by α-amanitin and actinomycin D. Tubulin genes are excluded from this domain, suggesting that it may exclusively be the transcriptional site of spliced leader genes. Trypomastigote forms of the parasite, which have reduced spliced leader transcription, show less RNA polymerase II labeling, and the spliced leader genes are more dispersed in the nucleoplasm. These results provide strong evidences that transcription of spliced leader RNAs occurs in a particular domain in the T. cruzi nucleus.
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Jung, Samil, Jae-Yeon Chun, Sei-Heun Yim, Soo-Suk Lee, Choong-Il Cheon, Eunsook Song et Myeong-Sok Lee. « Transcriptional regulation of histidine biosynthesis genes in Corynebacterium glutamicum ». Canadian Journal of Microbiology 56, no 2 (février 2010) : 178–87. http://dx.doi.org/10.1139/w09-115.
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Corynebacterium glutamicum , a gram-positive bacterium, has been widely used for industrial amino acid production. Corynebacterium glutamicum his genes are located and transcribed in two unlinked loci, hisEG and hisDCB–orf1–orf2–hisHA–impA–hisFI. The latter his operon starts the transcription at the C residue localized 196 bp upstream of the hisD ATG start codon. Our computer-based sequence analysis showed that the region corresponding to the untranslated 5′ end of the transcript, named the hisD leader region, displays the typical features of the T-box transcriptional attenuation mechanism. Therefore, expression of the cat reporter gene under the control of the wild-type or mutated hisD leader regions was tested in multi-copy (pProm and pTer series) and in single-copy (pInt series) systems under conditions of sufficient or limited histidine. Our mutational studies led to the conclusion that the CAU histidine specifier and 5′-UGGA-3′ sequence in the hisD leader region are required for the hisDCB–orf1–orf2–hisHA–impA–hisFI gene regulation. The cat gene expression from the wild-type leader region was negatively regulated by histidine. However, the cat gene expression from mutated leader regions was irresponsive to the level of histidine in the growth medium. Taken together, we propose that a T-box mediated attenuation mechanism is responsible for the gene expression of the hisDCB–orf1–orf2–hisHA–impA–hisFI operon in C. glutamicum.
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Song, Yue, Bahareh Zaheri, Min Liu, Sunil Kumar Sahu, Huan Liu, Wenbin Chen, Bo Song et David Morse. « Fugacium Spliced Leader Genes Identified from Stranded RNA-Seq Datasets ». Microorganisms 7, no 6 (11 juin 2019) : 171. http://dx.doi.org/10.3390/microorganisms7060171.
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Trans-splicing mechanisms have been documented in many lineages that are widely distributed phylogenetically, including dinoflagellates. The spliced leader (SL) sequence itself is conserved in dinoflagellates, although its gene sequences and arrangements have diversified within or across different species. In this study, we present 18 Fugacium kawagutii SL genes identified from stranded RNA-seq reads. These genes typically have a single SL but can contain several partial SLs with lengths ranging from 103 to 292 bp. Unexpectedly, we find the SL gene transcripts contain sequences upstream of the canonical SL, suggesting that generation of mature transcripts will require additional modifications following trans-splicing. We have also identified 13 SL-like genes whose expression levels and length are comparable to Dino-SL genes. Lastly, introns in these genes were identified and a new site for Sm-protein binding was proposed. Overall, this study provides a strategy for fast identification of SL genes and identifies new sequences of F. kawagutii SL genes to supplement our understanding of trans-splicing.
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Lodato, Patricia B., Elizabeth J. Rogers et Paul S. Lovett. « A Variation of the Translation Attenuation Model Can Explain the Inducible Regulation of the pBC16 Tetracycline Resistance Gene in Bacillus subtilis ». Journal of Bacteriology 188, no 13 (1 juillet 2006) : 4749–58. http://dx.doi.org/10.1128/jb.01937-05.
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ABSTRACT Expression of the tet resistance gene from plasmid pBC16 is induced by the antibiotic tetracycline, and induction is independent of the native promoter for the gene. The nucleotide sequence at the 5′ end of the tet mRNA (the leader region) is predicted to assume a complex secondary structure that sequesters the ribosome binding site for the tet gene. A spontaneous, constitutively expressed tet gene variant contains a mutation predicted to provide the tet gene with a nonsequestered ribosome binding site. Lastly, comparable levels of tet mRNA can be demonstrated in tetracycline-induced and uninduced cells. These results are consistent with the idea that the pBC16 tet gene is regulated by translation attenuation, a model originally proposed to explain the inducible regulation of the cat and erm genes in gram-positive bacteria. As with inducible cat and erm genes, the pBC16 tet gene is preceded by a translated leader open reading frame consisting of a consensus ribosome binding site and an ATG initiation codon, followed by 19 sense codons and a stop codon. Mutations that block translation of cat and erm leaders prevent gene expression. In contrast, we show that mutations that block translation of the tet leader result in constitutive expression. We provide evidence that translation of the tet leader peptide coding region blocks tet expression by preventing the formation of a secondary-structure complex that would, in the absence of leader translation, expose the tet ribosome binding site. Tetracycline is proposed to induce tet by blocking or slowing leader translation. The results indicate that tet regulation is a variation of the translation attenuation model.
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Tomšič, Jerneja, Brooke A. McDaniel, Frank J. Grundy et Tina M. Henkin. « Natural Variability in S-Adenosylmethionine (SAM)-Dependent Riboswitches : S-Box Elements in Bacillus subtilis Exhibit Differential Sensitivity to SAM In Vivo and In Vitro ». Journal of Bacteriology 190, no 3 (26 novembre 2007) : 823–33. http://dx.doi.org/10.1128/jb.01034-07.
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ABSTRACT Riboswitches are regulatory systems in which changes in structural elements in the 5′ region of the nascent RNA transcript (the “leader region”) control expression of the downstream coding sequence in response to a regulatory signal in the absence of a trans-acting protein factor. The S-box riboswitch, found primarily in low-G+C gram-positive bacteria, is the paradigm for riboswitches that sense S-adenosylmethionine (SAM). Genes in the S-box family are involved in methionine metabolism, and their expression is induced in response to starvation for methionine. S-box genes exhibit conserved primary sequence and secondary structural elements in their leader regions. We previously demonstrated that SAM binds directly to S-box leader RNA, causing a structural rearrangement that results in premature termination of transcription at S-box leader region terminators. S-box genes have a variety of physiological roles, and natural variability in S-box structure and regulatory response could provide additional insight into the role of conserved S-box leader elements in SAM-directed transcription termination. In the current study, in vivo and in vitro assays were employed to analyze the differential regulation of S-box genes in response to SAM. A wide range of responses to SAM were observed for the 11 S-box-regulated transcriptional units in Bacillus subtilis, demonstrating that S-box riboswitches can be calibrated to different physiological requirements.
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Hohenadl, Christine, Walter H. Gunzburg, Brian Salmons et Stanislav Indik. « The 5′ leader sequence of mouse mammary tumor virus enhances expression of the envelope and reporter genes ». Journal of General Virology 93, no 2 (1 février 2012) : 308–18. http://dx.doi.org/10.1099/vir.0.035196-0.
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Mouse mammary tumor virus (MMTV) is a complex betaretrovirus, which utilizes a Rev-like auxiliary protein Rem to export the unspliced viral RNA from the nucleus. MMTV env mRNA appears to be exported via a distinct, Rem-independent, mechanism. Here, we analysed the effect of an extensively folded region coinciding with the 5′ leader sequence on env gene expression. We found that the presence of the 5′ leader stimulates expression of the envelope protein. Enhanced Env production was accompanied by increased cytoplasmic levels of env mRNA. The 5′ leader promotes nucleocytoplasmic translocation and increases stability of env mRNA. The region responsible for this effect was mapped to the distal part of the 5′ leader. Furthermore, the 5′ leader inserted in the sense orientation into a heterologous luciferase expression construct increased luciferase activity.
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Tzani, Ioanna, Ivaylo P. Ivanov, Dmitri E. Andreev, Ruslan I. Dmitriev, Kellie A. Dean, Pavel V. Baranov, John F. Atkins et Gary Loughran. « Systematic analysis of the PTEN 5′ leader identifies a major AUU initiated proteoform ». Open Biology 6, no 5 (mai 2016) : 150203. http://dx.doi.org/10.1098/rsob.150203.
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Abundant evidence for translation within the 5′ leaders of many human genes is rapidly emerging, especially, because of the advent of ribosome profiling. In most cases, it is believed that the act of translation rather than the encoded peptide is important. However, the wealth of available sequencing data in recent years allows phylogenetic detection of sequences within 5′ leaders that have emerged under coding constraint and therefore allow for the prediction of functional 5′ leader translation. Using this approach, we previously predicted a CUG-initiated, 173 amino acid N-terminal extension to the human tumour suppressor PTEN. Here, a systematic experimental analysis of translation events in the PTEN 5′ leader identifies at least two additional non-AUG-initiated PTEN proteoforms that are expressed in most human cell lines tested. The most abundant extended PTEN proteoform initiates at a conserved AUU codon and extends the canonical AUG-initiated PTEN by 146 amino acids. All N-terminally extended PTEN proteoforms tested retain the ability to downregulate the PI3K pathway. We also provide evidence for the translation of two conserved AUG-initiated upstream open reading frames within the PTEN 5′ leader that control the ratio of PTEN proteoforms.
Thèses sur le sujet "Leader genes"
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East, A. K. « A study of the leader peptides of staphylococcal #BETA#-lactamases ». Thesis, University of Oxford, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233462.
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Ji, Yuanen. « Functional elements of the promoter, leader and intergenic spacer regions of ribosomal RNA operon(s) of mycobacteria ». Thesis, Open University, 1993. http://oro.open.ac.uk/57419/.
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This study was focused on the promoter and non-coding regions of the ribosomal RNA (rrn) operon(s) of mycobacteria; namely, the leader and the intergenic spacer regions. Two clones containing the promoter sequences of M .leprae and M. tuberculosis rrn operon were sequenced, their promoter elements were identified by primer extension experiments and by comparison with E.coli consensus promoter sequences. Their function was tested in E.coli and M. smegma tis . The sequences of the leader and intergenic spacer regions from eight and six species respectively were established after amplification by means of peR. Both leader and spacer regions contain antitermination elements and RNaseIII processing sites. The sequences established for these two regions also showed greater variability than the 168 rRNA gene and are suitable for phylogenetic studies. The sequences of the two rrn operons of M.smegmatis upstream from the 168 rRNA gene were cloned and sequenced. Their sequences showed that rrnI has a Box B element which is typical of slow-growers and that rrnII does not. Primer extension studies revealed that the rrn operon of slow-growers has a single promoter. In contrast multiple promoters were identified in the faster-growing M.smegmatis. Distinctive features, which are absent from slow-growers, were identified in the intergenic spacer regions of M.smegmatis.
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McDaniel, Brooke A. « Characterization of the S-adenosylmethionine-dependent regulation and physiological roles of genes in the S box system ». Connect to this title online, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1116765525.
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Thesis (Ph. D.)--Ohio State University, 2005.Title from first page of PDF file. Document formatted into pages; contains xvii, 176 p.; also includes graphics (some col.) Includes bibliographical references (p. 158-176). Available online via OhioLINK's ETD Center
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FILICE, NATALIA. « Valutazione clinica e radiografica del rimodellamento volumetrico degli innesti ossei autologhi nelle ricostruzioni maxillo-facciali delle creste atrofiche a fini impiantari ed analisi a cluster dei geni coinvolti nei processi di rimodellamento osseo ». Doctoral thesis, Università degli Studi di Milano-Bicocca, 2012. http://hdl.handle.net/10281/27988.
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SURGICAL-RADIOGRAPHIC PART:The aim of the present retrospective chart review was to determine the relationship between nonvascularized osseous graft remodeling and the three-dimensional (3D) features of grafts and recipient sites, the anatomical recipient regions and different graft procedures. 18 iliac crest were onlay-positioned in the mandible or maxilla or used in sinus lift procedures. CT scans, taken before implant positioning and after 1 year, revealed a mean volume resorption of 40%. For iliac crest grafts, the average resorption was 36% when the onlay was positioned in the anterior maxilla, 77% when it was positioned in the posterior mandible and 17% in sinus lift procedures.
GENIC PART: This part of the study aims to identify and rank genes involved in osseous augmentation or bone remodeling to obtain groups with more numerous predicted associations called the leader gene clusters. An iterative search (consisting of a consecutive expansion-filtering loop) was performed for which only genes involved in a specific process were identified. For each gene, predicted associations with all other involved genes were obtained from a Web-available database (Search Tool for the Retrieval of Interacting Genes/Proteins) and the weighted number of links (WNL), given by the sum of only high-confidence predicted associations (results with a score > or =0.9), allowing gene ranking. A total of 161 genes potentially involved in bone-volume augmentation and 128 genes connected with the bone-remodeling phenomenon were identified.
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Saha, Gopesh Chandra. « Mapping of foliar disease resistance genes and genes for agro-morphological traits in Lens culinaris Medik ». Pullman, Wash. : Washington State University, 2009. http://www.dissertations.wsu.edu/Dissertations/Fall2009/g_saha_112409.pdf.
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Keller, Daniel L. « Leaf epidermal morphology : a survey of the genus Allium ». Scholarly Commons, 1994. https://scholarlycommons.pacific.edu/uop_etds/2271.
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The epidermis from a range of species from the genus Allium was peeled from the base, middle, and tip of the adaxial and abaxial surfaces of leaf material. Epidermal peels were water mounted after being peeled using forceps, and photographed using Nomarski microscopy.
The epidermis is composed of rows of cells which run parallel to one another, and to the long axis of the leaf. Guard cells are present on both surfaces of the leaf in most species, but some species lack guard cells on either the abaxial or adaxial surface. Guard cells are sunken to varying degrees in all species surveyed. Subsidiary cells are lacking in all species surveyed. End walls of nonstomatal cells are either even or oblique. Micropapilae, striations, or trichomes are present in some species, but most species lack epidermal structures. Epidermal cells range in size from two to three times greater in length than width to greater than fifteen times longer than wide. The majority of parallel walls are either straight or diamond-shaped while others are wrinkled, wavy, or broadened.
Allium is separated into three groups according to the structure of the parallel walls. Group one includes those species with typically straight parallel walls; group two those species with diamond-shaped parallel walls; and group three is comprised of those species with wavy parallel walls.
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Yousef, Mary Roneh. « Characterization of the in vitro interaction between bacillus subtilis glyQS T Box leader RNA and tRNA(Gly) ». Connect to this title online, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1103744744.
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Thesis (Ph. D.)--Ohio State University, 2005.Title from first page of PDF file. Document formatted into pages; contains xv, 139 p.; also includes graphics (some col.) Includes bibliographical references (p. 123-139).
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Gonzalez-Carranza, Zinnia Hayde. « Characterization of a polygalacturonase gene expressed during abscission in Brassica napus L ». Thesis, University of Nottingham, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.287162.
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Levasseur, Liane. « Evolution of pre-mRNA spliced-leader (SL) trans- splicing in the deuterostomes and its role in monocistronic gene expression ». Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=117023.
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Spliced-leader (SL) trans-splicing is a splicesomal process by which the 5'-ends of diverse mRNAs are replaced by a common sequence originating from a specialized SL donor RNA. The patchy phylogenetic distribution of SL trans-splicing, including its recent discovery in the deuterostomes in the tunicate Ciona intestinalis presents two equally possible evolutionary histories. Either it is an ancestral eukaryotic trait that has been lost in multiple lineages, or, it was invented de novo in various lineages including the tunicates. SL trans-splicing has a known function in the resolution of polycistronic operons. However, for monocistronic transcripts there are many proposed but not substantiated functions, including the 5'-untranslated region (5'-UTR) sanitization hypothesis. I investigated the phylogenetic distribution of SL trans-splicing in the deuterostomes and its possible function as a 5'-UTR sanitization mechanism in the monocistronic troponin I gene (CiTnI) in Ciona. I produced oligo-capped 5'-RACE cDNA libraries to survey mRNA 5'-end sequences for common candidate SL sequences in the cephalochordate Branchiostoma, the hemichordate Saccoglossus and the echinoderm Strongylocentrotus. Following steps taken to eliminate short primer-related sequences created during the 5' oligo-capping reaction, and apparently hidden in the form of heteroduplex complexes, the cDNA libraries were subjected to 454 ultra high-throughput sequencing. Several indicators, including the presence of 5'-TOP sequences at the 5'-termini of mRNAs encoding ribosomal proteins and translation factors showed that the 5'-RACE libraries effectively represented the extreme 5'-termini of mRNAs. No common 5'-ends that could represent SL sequences were observed in any of the species examined. This result strongly supports the independent evolution of SL trans-splicing in the tunicates. To further examine the postulated functional role of SL trans-splicing in removing deleterious sequences from the 5'-UTR, I made and used an internal transfection control construct to validate the observation, previously made in our lab, that an experimental CiTnI reporter construct with a long retained-outron 5'-UTR showed low reporter gene activity when electroporated in Ciona embryos. I then created a new CiTnI construct to directly assess the possible presence of a specific deleterious element in the long retained-outron 5'-UTR. My results clearly indicated that there is no specific deleterious element, but that it is the length of the retained-outron 5'-UTR, per se, that leads to low TnI reporter construct expression.Le “spliced-leader” (SL) trans-épissage est un processus dépendant du spliceseome dont l'éxtremité 5' de divers ARNms sont remplacés par une séquence commune dérivant d'un SL ARN donneur spécialisé. À cause de sa répartition phylogénétique compliquée et sa découverte récente dans le tunicier Ciona intestinalis, un deutérostomiens, il existe deux possibilités d'évolution plausible pour le SL trans-épissage. Le SL trans-épissage est soit; un caractère ancestral qui s'est perdu plusieurs fois dans différentes lignées où il s'est inventé de novo dans différentes lignées, y compris les tuniciers. Une des fonctions connues du SL trans-épissage est la résolution de transcrits polycistroniques, cependant sa fonction concernant les transcrits monocistroniques est moins évidente. Il existe plusieurs hypothèses en ce qui concerne la fonction du SL trans-épissage de gènes monocistroniques, une d'entre-elles est l'assainissement des régions 5' non-traduit (5'-UTR). Mes travaux de recherche ont portés sur la répartition phylogénétique de SL trans-épissage dans les deutérostomiens et sa fonction en tant d'assainissement de la région 5' non-traduite pour le gène troponine I (CiTnI) de Ciona. J'ai créé des banques d'ADNc 5'-RACE coiffés d'oligonucleotide pour bien étudier les séquences à l'extrémité 5' de différents ARNms et ainsi découvrir un motif SL commun dans le Branchiostoma céphalochordé, le Saccoglossus hemichordate et le Strongylocentrotus échinodermes. Après avoir éliminé les courtes séquences reliées à l'amorce qui se sont crée au cours de la réaction de coiffe des ARNs et qui étaient apparemment cachées sous forme de complexes hétéroduplexes, les banques d'ADNc ont été soumises au séquençage 454 ultra à haut débit. La présence des séquences 5'-TOP sur les ARNms des proteines ribosomique et gènes de facteurs de traduction était un des indicateurs confirmant que les banques comprenaient des extrémités 5' de ARNm de qualité. Des extrémités 5' en communs, qui pourraient représenter des séquences SL, n'ont pas été observées dans les organismes examinés. Ce résultat appuie fortement l'évolution indépendante de SL trans-épissage dans les tuniciers.Pour examiner davantage le rôle d'élimination des séquences néfastes de la 5'-UTR postulé pour le SL trans-épissage, j'ai produit et utilisé un contrôle interne de transfection. Ce contrôle a été construit afin de valider des résultats obtenus il y a quelques années dans notre laboratoire, qu'un rapporteur expérimental de CiTnI qui contient un outron-5'-UTR non-épissé a une faible activité du gène rapporteur lorsqu'électroporé dans des embryons de Ciona. Ensuite, j'ai créé un nouveau rapporteur CiTnI pour évaluer la présence possible d'un élément néfaste dans la séquence du 5'-UTR. Mes résultats indiquent qu'il n'y a aucun élément néfaste spécifique, mais que la longueur du outron-5'-UTR retenu, en soi, mène à la faible expression du rapporteur TnI.
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Hagerman, Lena. « Att skapa ledare – genus- organisations- och maktperspektiv på ledarskapsutvecklingCreating Leaders- Gender, Organization and Power : a New Perspective ». Thesis, Kristianstad University College, Department of Humanities and Social Sciences, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:hkr:diva-3797.
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Uppsatsens fokus utgörs av den tröghet som präglar processen mot en jämnare köns-fördelning på samhällets högre chefspositioner. Den inleds med en kartläggning av aktuell forskning, som omfattar områdena genus och ledarskap, ledarskapsutbildning, organisationskultur och makt samt en intervjuundersökning som kompletteras med policydokumentanalys. Utifrån analysen som materialet genererar drar jag slutsatser som resulterar i förslag till en alternativ ledarskapsutbildning. Uppsatsens primära syfte är att genom litteraturstudie, kvalitativt upplagda intervjuer med personer på chefsbefattningar, chefsutvecklare, pedagoger inom ledarskapsutveckling, kreativt skrivande och rollspel samt dokumentanalys undersöka förutsättningarna för kvinnli-ga chefer och ledare. Det sekundära syftet är att motivera upplägget på en ledarskaps-utbildning, som både möjliggör en könsutjämning och erbjuder en mall för kreativ le-darskapsutveckling oavsett tidigare hierarkier och strukturer. I min analysmodell av dikotomierna chefsskap – ledarskap finns en kvantitativ ansats. För övrigt präglas uppsatsen av ett holistiskt, tvärvetenskapligt förhållningssätt vilket även gäller val av metoder, både i empiridelen och analysarbetet. Att påverka den rådande normativa ordningen kräver ett alternativt sätt att tänka vilket presenteras i uppsatsens slutana-lys. Den består av en modell för tänkandets utveckling samt förslag till en ledar-skapsutbildning som omfattar tekniker för förändring på individnivå samt en alterna-tiv analys av organisationsstrukturer.
Livres sur le sujet "Leader genes"
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Davie, Michael B. Winning ways : Innovative leaders discuss their success strategies. [Ancaster, Ont.] : Manor House Pub., 2002.
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How They Achieved. New York : John Wiley & Sons, Ltd., 2001.
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What is a Gospel ? : The genre of the canonical Gospels. Macon, Ga : Mercer University Press, 1985.
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Wyatt, Tristram D. 3. How behaviour develops. Oxford University Press, 2017. http://dx.doi.org/10.1093/actrade/9780198712152.003.0003.
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Behaviours evolve by natural selection. As genes influence how behaviours develop, selection on behaviour will alter gene frequencies in subsequent generations: genes that lead to successful behaviours in foraging, parental care, or mate choice, for example, will be represented in more individuals in future generations. If conditions change, then mutations of the genes that give rise to advantageous behaviours will be favoured by selection. ‘How behaviour develops’ explains that the environment is equally important: both genes and environment are intimately and interactively involved in behaviour development. Behavioural imprinting is also discussed along with co-opting genes, gene regulation, social influences on brain gene expression, phenotypic plasticity, and play.
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Switch : Activating Your Genes for a Leaner, Longer, Healthier Life. Simon & Schuster, Limited, 2020.
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Shane, Scott. Born Entrepreneurs, Born Leaders : How Your Genes Affect Your Work Life. Oxford University Press, 2010.
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Business Leader Profiles for Students. 2e éd. Thomson Gale, 2002.
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Business Leaders : Steve Jobs (Korean Edition). Myeongjin Chulpansa/Tsai Fong Books, 2009.
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Gorman, Jack M. Life Events Shape Us. Oxford University Press, 2018. http://dx.doi.org/10.1093/med/9780190850128.003.0003.
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Psychiatry downplayed the importance of life events in causing mental illness from the 1960s on, favoring a view that all disorders except one are the result of abnormal genes affecting chemical processes in the brain. Studying the exception, posttraumatic stress disorder (PTSD), when it was defined in 1980 helped lead to renewed recognition that early life adversity is central to all psychiatric conditions. At the same time, neuroscientists showed that early life experiences are capable of changing life-long behavior and brain function in laboratory animals. One mechanism by which this occurs is through the epigenetic regulation of gene expression. Epigenetics is the way that the expression levels of genes are controlled without changing the underlying genetic code. Epigenetics is an attractive way of understanding how individual life experiences are translated in the brain into each person’s unique set of emotions, behaviors, abilities, and risks for psychiatric abnormalities.
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Biloshytsky, Vadym, et Roman Cregg. Pioneering use of gene therapy for pain. Sous la direction de Paul Farquhar-Smith, Pierre Beaulieu et Sian Jagger. Oxford University Press, 2018. http://dx.doi.org/10.1093/med/9780198834359.003.0083.
Texte intégralRésumé :
The landmark paper discussed in this chapter is ‘Gene therapy for pain: Results of a Phase I clinical trial’, published by Fink et al. in 2011. In this study, the first of its kind, researchers studied the efficacy and safety of a modified herpes simplex virus (HSV) vector used to deliver PENK, which encodes proenkephalin, which is cleaved into the enkephalin peptides Met-enkephalin and Leu-enkephalin, which induce analgesia by acting on opioid receptors. The development of the HSV vector was based in part on results studies in which adenovirus, adeno-associated virus, or non-viral vectors were used to overexpress genes. Overexpression of a variety of large molecules leads to a reduction in pain-related behaviour in animals. Gene therapy in the treatment of chronic pain seems to offer a promising alternative to systemic or highly invasive therapies. However, additional research is needed to determine the safety, effectiveness, and cost-efficiency of this approach.
Chapitres de livres sur le sujet "Leader genes"
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Ayliffe, Michael, Ming Luo, Justin Faris et Evans Lagudah. « Disease Resistance ». Dans Wheat Improvement, 341–60. Cham : Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-90673-3_19.
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AbstractWheat plants are infected by diverse pathogens of economic significance. They include biotrophic pathogens like mildews and rusts that require living plant cells to proliferate. By contrast necrotrophic pathogens that cause diseases such as tan spot, Septoria nodurum blotch and spot blotch require dead or dying cells to acquire nutrients. Pioneering studies in the flax plant-flax rust pathosystem led to the ‘gene-for-gene’ hypothesis which posits that a resistance gene product in the host plant recognizes a corresponding pathogen gene product, resulting in disease resistance. In contrast, necrotrophic wheat pathosystems have an ‘inverse gene-for-gene’ system whereby recognition of a necrotrophic fungal product by a dominant host gene product causes disease susceptibility, and the lack of recognition of this pathogen molecule leads to resistance. More than 300 resistance/susceptibility genes have been identified genetically in wheat and of those cloned the majority encode nucleotide binding, leucine rich repeat immune receptors. Other resistance gene types are also present in wheat, in particular adult plant resistance genes. Advances in mutational genomics and the wheat pan-genome are accelerating causative disease resistance/susceptibility gene discovery. This has enabled multiple disease resistance genes to be engineered as a transgenic gene stack for developing more durable disease resistance in wheat.
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Boycheva, Irina, Ralitsa Georgieva, Lubomir Stoilov et Vasilissa Manova. « Effects of light and UV-C radiation on the transcriptional activity of COP1 and HY5 gene homologues in barley. » Dans Mutation breeding, genetic diversity and crop adaptation to climate change, 478–86. Wallingford : CABI, 2021. http://dx.doi.org/10.1079/9781789249095.0049.
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Abstract Photomorphogenic regulators COP1 (Constitutive Photomorphogenic 1) and HY5 (Elongated Hypocotyl 5) play a key role in plant development by guiding the transition from dark to light growth. In Arabidopsis they are also implicated in the transcriptional control of photolyase genes. Here we characterize the transcript abundance of COP1 and HY5 gene homologues in barley in relation to light-grown conditions and UV-damage response. Etiolated and green 6-day-old seedlings were UV-C irradiated and exposed to light or kept in darkness. The abundance of barley COP1 and HY5 transcripts was assessed by real-time RT-PCR. In etiolated leaves we found several-fold lower levels of COP1 transcripts which reached the levels of the green ones after 1 h of light exposure. Barley HY5 transcripts were very low in the dark-grown seedlings and after 1 h of illumination they increased drastically to levels significantly exceeding those measured in the green leaves. Both genes were upregulated by light in the irradiated plants as well, but to a lesser extent compared with their controls, probably due to the presence of non-repaired DNA damage in the etiolated leaves soon after irradiation. The enhanced transcription of barley COP1 under light is unexpected in view of the well-known function of COP1 as a negative regulator of plant photomorphogenesis but conforms to the positive role reported for AtCOP1 in UV-B signalling. HY5 is recognized as a stimulator of light-inducible genes and our data support such a role for the barley HY5 homologue as well. Our study shows that, in barley seedlings, the regulation of COP1 and HY5 gene expression is achieved through light-positive transcriptional modulation, suggesting that both genes contribute to the de-etiolation phase in barley. According to our knowledge, this is the first quantitation of the COP1 and HY5 mRNAs in barley that also regards the UV-damage response of this crop.
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Gehrke, Lee, et Stephen A. Jobling. « Untranslated Leader Sequences and Enhanced Messenger RNA Translational Efficiency ». Dans Post-Transcriptional Control of Gene Expression, 389–98. Berlin, Heidelberg : Springer Berlin Heidelberg, 1990. http://dx.doi.org/10.1007/978-3-642-75139-4_36.
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Baum, Christopher, Hans-Georg Eckert et Wolfram Ostertag. « Contribution of the Retroviral Leader to Gene Transfer and Expression in Packaging Cells and Myeloid Stem and Progenitor Cells ». Dans Gene Technology, 219–28. Berlin, Heidelberg : Springer Berlin Heidelberg, 1996. http://dx.doi.org/10.1007/978-3-642-61122-3_16.
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Ross, Samuel E., et Ozren Bogdanovic. « Generation and Molecular Characterization of Transient tet1/2/3 Knockouts ». Dans Methods in Molecular Biology, 281–318. New York, NY : Springer US, 2021. http://dx.doi.org/10.1007/978-1-0716-1294-1_17.
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Abstract5-methylcytosine (5mC) is a gene-regulatory mark associated with transcriptional repression. 5mC can be erased through the catalytic action of Ten-eleven translocation (TET) methylcytosine dioxygenases (TET1, TET2, TET3), which oxidize 5mC resulting in its removal from the genome. In vertebrates, TET enzymes facilitate DNA demethylation of regulatory regions linked to genes involved in developmental processes. Consequently, TET ablation leads to severe morphological defects and developmental arrest. Here we describe a system that can facilitate the study of relationships between TET enzymes, 5mC, and embryo development. We provide detailed descriptions for the generation of F0 zebrafish tet1/2/3 knockouts using CRISPR/Cas9 technology and elaborate on the strategies to assess the impact of TET loss by reduced representation bisulfite sequencing (RRBS).
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Jamaloddin, Mohammed, Anumalla Mahender, C. Guru Gokulan, Chintavaram Balachiranjeevi, A. Maliha, Hitendra Kumar Patel et Jauhar Ali. « Molecular Approaches for Disease Resistance in Rice ». Dans Rice Improvement, 315–78. Cham : Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-66530-2_10.
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AbstractRice production needs to be sustained in the coming decades, with changing climatic conditions becoming more conducive to the prevalence of disease outbreaks. Major rice diseases collectively cause enormous economic damage and yield instability. Breeding for disease-resistant rice varieties could be one of the best options to counter these disease outbreaks. Disease-screening protocols and newer technologies are essential for effective phenotyping and would aid in gene discovery and function. Understanding the genetics of disease mechanisms and stacking of broad-spectrum disease-resistance genes could lead to faster development of rice varieties with multiple disease resistance. New molecular breeding approaches are discussed for the development of these varieties. The molecular biology of disease resistance is now better understood and could be well manipulated for improved resilience. Transgenic approaches for disease resistance are discussed. Genome-editing tools for the development of disease-resistant rice varieties are thoroughly discussed. The use of bioinformatics tools to speed up the process and to obtain a better understanding of molecular genetics mechanisms of disease resistance is explained.
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Bag, Debojyoti, Aliya Tabassum, Nidhi Arora, Praveen Kumar Verma et Sanghapal D. Sawant. « Medicinal Applications of Cannabidiol from the Genus Cannabis L. » Dans Botanical Leads for Drug Discovery, 201–41. Singapore : Springer Singapore, 2020. http://dx.doi.org/10.1007/978-981-15-5917-4_10.
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Michael, T., A. Wilson, Keith Saunders, Mandy J. Dowson-Day, David E. Sleat, Hans Trachsel et Karl W. Mundry. « Effects of the 5′-Leader Sequence of Tobacco Mosaic Virus RNA, or Derivatives Thereof, on Foreign mRNA and Native Viral Gene Expression ». Dans Post-Transcriptional Control of Gene Expression, 261–75. Berlin, Heidelberg : Springer Berlin Heidelberg, 1990. http://dx.doi.org/10.1007/978-3-642-75139-4_25.
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Sofkova-Bobcheva, Svetla, Ivelin Pantchev, Ivan Kiryakov, Petar Chavdarov, Yordan Muhovski, Fatma Sarsu et Nasya Tomlekova. « Induced mutagenesis for improvement of bean (Phaseolus vulgaris L.) production in Bulgaria. » Dans Mutation breeding, genetic diversity and crop adaptation to climate change, 178–93. Wallingford : CABI, 2021. http://dx.doi.org/10.1079/9781789249095.0018.
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Abstract Although historically a surplus food producer, Bulgarian agriculture has faced a downturn in recent decades. Local legume cultivars have lost favour with farmers and the canning industry, due to their low productivity in comparison with imported ones. Diseases and abiotic stresses are the most important factors limiting the production of edible legumes, costing farmers hundreds of euros in lost revenue each year. The overall objective of our ongoing bean mutation breeding programme was to enrich the gene pool of Phaseolus vulgaris L. and to develop genotypes resistant to Xanthomonas axonopodis pv. phaseoli (Smith) (Xap) and Pseudomonas savastanoi pv. phaseolicola (Burkh.) (Psp) using EMS. An elite line and common cultivar (an heirloom and a snap bean type) in Bulgaria, were selected as parents and the chemical mutagen EMS was used for generating mutations. In total, 1000 seeds were treated and the two generated M1 populations were grown in the field. All M2 mutant plants (1650 from initial line IP564 and 2420 from initial cultivar 'Mastilen 11b') were grown in field conditions and a number of phenotypic changes were observed on these mutated plants. They were also screened for Xap disease resistance via leaf artificial inoculation under greenhouse conditions. Individual plant selection was performed for the putatively resistant M2 plants. In the M3 generation these lines were screened using artificial inoculation with Xap and Psp pathogens (leaves and pods) under field conditions. Selected M3-M4 lines with confirmed disease resistance were tested for fresh pod quality. Yield tests were started in M4 and M5 generations and, according to their productivity performance, mutants were advanced to the M6/M7 generation for validation. The expression patterns of genes putatively involved in the resistance reactions towards two races of Psp were determined using qRT-PCR for the specific and reference genes. In conclusion, 50 plants with visible morphological changes and/or increased tolerance to the two targeted bacterial diseases were selected. A total of 20 advanced mutant bean lines are currently being evaluated for their competitiveness in multiple sites.
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Camelo, Felipe, et Anne Le. « The Intricate Metabolism of Pancreatic Cancers ». Dans The Heterogeneity of Cancer Metabolism, 77–88. Cham : Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-65768-0_5.
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AbstractCurrently, approximately 95% of pancreatic cancers are pancreatic ductal adenocarcinomas (PDAC), which are the most aggressive form and the fourth leading cause of cancer death with extremely poor prognosis [1]. Poor prognosis is primarily attributed to the late diagnosis of the disease when patients are no longer candidates for surgical resection [2]. Cancer cells are dependent on the oncogenes that allow them to proliferate limitlessly. Thus, targeting the expression of known oncogenes in pancreatic cancer has been shown to lead to more effective treatment [3]. This chapter discusses the complexity of metabolic features in pancreatic cancers. In order to comprehend the heterogeneous nature of cancer metabolism fully, we need to take into account the close relationship between cancer metabolism and genetics. Gene expression varies tremendously, not only among different types of cancers but also within the same type of cancer among different patients. Cancer metabolism heterogeneity is often prompted and perpetuated not only by mutations in oncogenes and tumor-suppressor genes but also by the innate diversity of the tumor microenvironment. Much effort has been focused on elucidating the genetic alterations that correlate with disease progression and treatment response [4, 5]. However, the precise mechanisms by which tumor metabolism contributes to cancer growth, survival, mobility, and aggressiveness represent a functional readout of tumor progression (Fig. 1).
Actes de conférences sur le sujet "Leader genes"
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Cool, D. E., et R. T. A. MacGillivray. « CHARACTERIZATION OF THe HUMAN FACTOR XII GENE ». Dans XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1642800.
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Surface activation of the plasma systems involved with coagulation, fibrinolysis, renin formation and kinin generation involves factor XII (Hageman factor). This protein is a 76,000 dalton glycoprotein which circulates in plasma as an inactive form of a serine protease. A human liver cDNA coding for factor XII was used to screen a human genomic phage library. Two overlapping clones were isolated, XHXII27 and XHXII76, and contain the entire gene for human factor XII. The gene is 13.5 Kbp in length and consists of 14 exons and 13 introns. The transcriptional start site of the mRNA was determined using S1 mapping and primer extension analysis. The results indicate that the 5′ untranslated end of the mRNA has a leader sequence of 47 bp and is not interrupted by an intron in the gene. DNA sequence analysis of the region upstream of the transcriptional start site does not contain TATA or CAAT sequences, which are often found in other genes transcribed by RNA polymerase II. The positions of the introns in the coding sequence separate the protein into domains which are homologous to similar regions found in fibronectin and tissue-type plasminogen activator. Furthermore, wherever protein homologies are found, the positions of the introns in the triplet codon occur in the same reading frame as in the tissue-type plasminogen activator, urokinase plasminogen activator and factor XII genes. The intron/exon organization of the factor XII gene is different to the organization of other coagulation genes such as prothrombin, factor IX and factor X. Therefore, factor XII appears to have evolved as a member of the plasminogen activator family of genes rather than as a member of the clotting factor gene family.
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O'hara, Patrick J., Frank A. Grant, A. Betty, J. Haldmen et Mark J. Murray. « Structure of the Human Factor VII Gene ». Dans XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643786.
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Factor VII is a member of a family of vitamin K-dependent, gamma-carboxylated plasma protein which includes factor IX, factor X, protein C, protein S and prothrombin. Activated factor VII (factor Vila) is a plasma serine protease which participates in a cascade of reactions leading to the coagulation of blood. Two overlapping genomic clones containing sequences encoding human factor VII were isolated and characterized. The complete sequence of the gene was determined and found to span 12.8 kilobases. The mRNA for factor VII as demonstrated by cDNA cloning is polyadenylated at multiple sites but contains only one AAUAAA poly-A signal sequence. The mRNA can undergo alternative splicing forming one transcript containing eight segments as exons and another with an additional exon which encodes a larger pre-pro leader sequence. The portion of the pre-pro leader coded for by the additional exon has no known counterpart in the other vitamin K-dependent proteins. The positions of the introns with respect to the amino acid sequence encoded by the eight essential exons of factor VII are the same as those present in factor IX, factor X, protein C and the first three exons of prothrombin. These exons code for domains generally conserved among members of this gene family, including a pre-pro leader (the essential exon la and alternative exon lb), a gamma-carboxylated domain (exons 2 and 3) a growth factor domain (exons 4 and 5) an activation region (exon 6) and a serine protease (exon 8). The corresponding introns in these genes are dissimilar with respect to size and sequence, with the exception of the third intron in factor VII and protein C. Four introns and a portion of exon 8 in factor VII contain regions made up of tandem repeats of oligonucleotide monomer elements. More than a quarter of the intron sequences and more than a third of the 3' untranslated portion of the mRNA transcript consist of these minisatellite tandem repeats. This type of structure is responsible for polymorphisms due to allelic variation in repeat copy number in other areas of the human genome. Tandem repeats can evolve as a result of random crossover in DNA whose sequence is not maintained by selection. This suggests that much of the sequence information present in the introns and untranslated portion of the message is dispensable.
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Li, Ling. « CRISPR/Cas9-based editing of OsNF-YC4/GmNF-YC4 promoter yields high-protein crops ». Dans 2022 AOCS Annual Meeting & Expo. American Oil Chemists' Society (AOCS), 2022. http://dx.doi.org/10.21748/qsgt8379.
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Genome editing is a new breeding technology widely touted for transgene-free crop improvement; however, to date, the majority of derived traits are created through gene knockout. We describe a novel approach using gene editing to upregulate gene expression by removing negative repressor binding motifs. Our previous work demonstrated that ectopic expression of NF-YC4 increases protein content of leaves and seeds at the expense of carbohydrates. We detected several conserved motifs predicted to be bound by repressors in the promoter of rice and soybean NF-YC4 genes. Using CRISPR/Cas9 to edit the promoters of rice and soybean NF-YC4 genes, we deleted promoter fragments harboring repressor binding motifs. Those deletions resulted in decreased repressor binding, increased NF-YC4 expression, increased protein and decreased carbohydrates. Gene-edited plants showed up to 48% higher leaf protein and 15% increased seed protein. Moreover, we exemplify a general approach for upregulating gene expression through targeted genomic deletions.
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Busby, S., K. Berkner, L. Halfpap, J. Gambee et A. Kumar. « ALTERATION OF PROPTIDE SEQUENCE IMPAIRS BIOLOGICAL ACTIVITY OF HUMAN FACTOR VII ». Dans XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643784.
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We have investigated the effect of altering the leader sequence of human factor VII on its biological activity. Factor VII is a vitamin K-dependent blood coagulation protein whose activity depends on the presence of gamma-carboxyglutamic acid (gla) residues in its amino terminal region. Since factor VII and other vitamin K-dependent proteins exhibit structural homology in the propeptide, it has been suggested that the propeptide is involved in gamma-carboxylation. Recently, two factor IX patients were identified with point mutations which prevented the processing of the propeptide and generated a factor IX with greatly reduced biological activity (Diuguid et al., PNAS 83; 5803; Bentley et al., Cell 45: 343). To examine this question using recombinant DNA technology, we altered the sequence of the factor VII propeptide by in vitro mutagenesis of the factor VII cDNA and then expressed the altered genes in baby hamster kidney (BHK) cells. For the 60 and 38 aa leader forms of factor VII, the arg (R) at -1 was changed to ser (S), yielding the sequence HRRRS before the +1 ala. In addition, for the 60 aa leader form, a ser was inserted after the arg at -1, resulting in the sequence HRRRRS before the +1 ala. As determined by ELISA, the mutant proteins were synthesized and secreted by BHK cells at levels comparable to the wild-type forms of factor VII. Analysis by radioimmune precipitation and SDS-PAGE indicated that substitution of arg by ser at -1 prohibits processing of the factor VII propeptide, whereas, insertion of a ser after the four arg's does not. However, all three proteins have reduced biological activity by approximately 5-fold when compared to the wild-type forms with the one-stage clotting assay. All three proteins are also quantitatively precipitated by Ba citrate, indicating they are at least partially gamma-carboxylated. These results suggest that the correct sequence of the propeptide, not just cleavage of the propeptide, is necessary for generating a biologically active molecule. The effect of these sequence alterations on gamma-carboxylation will be evaluated further by analysis of the amino acid sequence and composition of the mutant proteins.
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Muntyan, Victoria S., Alla S. Saksaganskaia, Alexey N. Muntyan, Mariia E. Vladimirova et Marina L. Roumiantseva. « STRESS AND IMMUNITY OF NODULE BACTERIA SINORHIZOBIUM MELILOTI : LOCALIZATION, POLYMORPHISM AND PHYLOGENY OF GENETIC DETERMINANTS ». Dans 22nd SGEM International Multidisciplinary Scientific GeoConference 2022. STEF92 Technology, 2022. http://dx.doi.org/10.5593/sgem2022/6.1/s25.15.
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Sinorhizobium meliloti are agriculturally valuable species of soil bacteria that form nitrogen-fixing symbiosis with alfalfa plants. Global climate changes lead to an increase of agricultural areas subjected to salinity. Current knowledge about about high-salt stress impact on soil saprophitic root nodulated microsymbionts of legumes is weakly studied and rhizobia gene pool responsible for salt tolerance are fragment and far from clear. An increase of bacteria nonspecific resistance (immune status) to unfavorable stress factors can occur through the induction of defense mechanisms like restrictionmodification systems and CRISPR/cas systems which are aimed to protect bacteria cells from bacteriophages widespread in soil microbiome. The aim of this research was to evaluate the role of the megaplasmid pSymA in the formation of ecological genome of S. meliloti, which is related to stress tolerance and to determine the location of elements of adaptive immune systems protecting root nodule bacteria against external foreign DNA. The analysis was done on 11 genes, products of which involved in response to ion stress and synthesis of osmoprotectors. It was found that 6 out of 11 genes were found in the genomes of all analyzed S. meliloti strains, while it was not a case for other 5 genes. It was found that, unlike chromosome, megaplasmid I of S. meliloti accumulated copies of 4 from 5 genes, except kdpA gene, which is represented by a single copy and localized on megaplasmid I in all so far studied strains. It was predicted that closest phylogenetic relatives of genes whose products are involved in response to ion stress as well in synthesis of osmoprotectors are homologous genes of closely related S. medicae species. The exception was for betI2, for which the closest phylogenetic relative was homologous gene of Klebsiella pneumonia, and another exception is kdpA gene introduced onto megaplasmid-I from actinobacteria. Regarding elements of immune systems it was revealed that nonsymbiotic plasmids of S. meliloti harbored incomplete elements of RMS-I, -II, and - III systems, while the 4 complete RMS-IV systems were detected on a single plasmid. It was found out that corresponding methylases had similarities with similar enzymes detected in nitrogen-fixing strains of Agrobacterium tumefaciens, Mezorhizobium sp., Bradyrhizobium sp. CRISPR sequences were not detected on megaplasmid-I, while they were on chromosome, megaplasmid-II and on cryptic plasmids. So, it was concluded that megaplasmid-I of S. meliloti are enriched in copies of genes related to osmotic stress tolerance, but it role in immune status of rhizobia is requested further elucidation.
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Manukyan, I. R., et N. N. Dogusova. « Resistance of winter wheat cultivars to leaf rust in conditions of the Central Caucasus ». Dans General question of world science. Наука России, 2021. http://dx.doi.org/10.18411/gq-31-03-2021-14.
Texte intégralRésumé :
The main problem of wheat immunity to leaf rust is the loss of efficiency of most Lrgenes. The decrease in efficiency is associated with microevolutionary processes within the population and the emergence of new virulent phytopathogen races that can overcome previously efficient resistance genes. The article presents the results of the phytopathological test and marker analysis of the selected material of winter wheat for resistance to the leaf rust pathogen (Puccinia recondita Rob.ex Desm f. sp. tritici.). The object of the research was 20 cultivar samples of various ecological and geographical origins. DNA was isolated from the leaves of 10-day-old wheat germs. Molecular markers were used for the following genes: Lr9 (SCS5), Lr10 (Fi.2245/Lr10-6/r2), Lr19/Sr25 (SCS265), Lr20/Sr15 (STS638), Lr24/Sr24 (Sr24#12), Lr34/Sr57 (csLV34), Lr37/Sr38/Yr17/Pch2/Cre5 (Ventriup/LN2), Lr41 (GDM35), Lr47 (PS10). Using molecular markers, the studied wheat varieties did not reveal the highly and partially effective genes Lr9, Lr19/Sr25, Lr24/Sr24, Lr41, and Lr47 in Russia, and the ineffective gene Lr20/Sr1. As a result of molecular screening, it was found that the List 25 variety had Lr37 genes; the Mif variety had Lr10 genes; the Eltan variety had Lr10 genes; the Markola variety had Lr34 genes; the Malvina variety had Lr26 genes; the Tvorets variety had Lr10 genes; the DB 1/05 variety had Lr10 genes; the Evklid variety had Lr10 genes; the Sumai aut variety had Lr34 genes; the Lebidka odes'ka variety had Lr34 genes; the Solara variety – Lr34; the Zhiva variety – Lr10, Lr34. When comparing the results of marker analysis with field resistance to leaf rust, the resistant type of reaction to infection (R) was shown by the cultivars: Battum, Eltan, Evklid, Areal, and Solara; the susceptible type of reaction (S) was noted in the cultivars Markola and Mallyska; the medium susceptible type of reaction (MS) – in the cultivars Lebidka odes'ka and Tvorets.
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Eltai, Nahla O., Sara H. Al-Hadidi, Asmaa A. Al Than, Sanjay H. Doiphode et Hadi M. Yassine. « Salmonellosis among Pediatric Population in Qatar : Prevalence, Antibiotic Resistance and Molecular Epidemiology ». Dans Qatar University Annual Research Forum & Exhibition. Qatar University Press, 2020. http://dx.doi.org/10.29117/quarfe.2020.0126.
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Objectives: This study aims to characterize at the molecular level the genes encoding resistance in Salmonella and explain the molecular mechanisms underlying resistance to ceftriaxone, cefepime, amoxicillin-clavulanate, tetracycline, trimethoprim-sulfamethoxazole, chloramphenicol, colistin and azithromycin in Salmonella. It aims as well to characterize the 16S rRNA gene region by restriction fragment length polymorphism (RFLP) to investigate if this region constitutes an appropriate ‘coincidental’ marker to distinguish important pathogenic Salmonella species. Finally, determine the lineages of Salmonella species and evolutionary relationships among bacteria classified within the same genus. Methodology: 246 Salmonella isolates were collected from children under 16 years old during Jan. 2018 - Dec 2019, presented with gastroenteritis at Hamad Medical Corporation. Isolates were tested for antibiotic susceptibility against nineteen relevant antibiotics using E-test. Isolates that harbor antibiotic resistance were confirmed using PCR specific primers for 38 genes. In addition, the variable region of class 1 and 2 integrons were identified by PCR among amoxicillin-clavulanate (AMC) resistant samples. RFLP targeting16S rRNAwas performed using seven restriction enzymes including AluI, Bgl I, Bgl II, EcoR I, SmaI, Hinf I & Hae III. Results: Resistance was detected against 15 antibiotics and (38.2%) of isolates were resistant to at least one antibiotic. Overall, high resistance was reported to tetracycline (23.9%), ampicillin (21.1%), AMC (18.7%) and sulfamethoxazoletrimethoprim (13%). Further, 22.4% of the isolates were multidrug-resistant (MDR), with 4.1% being ESBL producers. 90 % of ESBL producers had one of bla CTX-M-Group. Class (1) AMC resistant samples showed the highest resistance to different antibiotics. 16S rRNA-RFLP analysis divided Salmonella isolates into two main groups. Conclusion: Our results indicate a high antimicrobial resistance pattern of Salmonella, which necessities the development of regulatory programs to combats antimicrobial resistance. In particular, our results showed high resistance to Class (1) AMC cassette that involves the transmission and expression of the resistance. This might lead to a concern of increased multidrug resistance in the future. This study provides evidence guidance to activate and implement the pillars of an antimicrobial stewardship program in animal and human health to reduce MDR salmonellosis.
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Fowlkes, P. M., P. K. Lund, M. Blake et J. Snouwaert. « THE REGULATION OF FIBRINOGEN PRODUCTION INVOLVES AT LEAST ONE OTHER HEPATOCYTE GENE ». Dans XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1644317.
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It is currently thought that glucocorticosteriods have a direct effect on the transcription of the alpha, beta and gamma fibrinogen genes. However, our studies indicate that while corticosteriods play a role in fibrinogen production, this role is not due to transcriptional activation via glucocorticosteriod receptors. In initial experiments, we compared the levels of fibrinogen mRNA in hepatocytes isolated from hypophysectomized rats to those from control animals. The levels of mRNA in hypophysectomized rats, which produce little ACTH or corticosteriods, were significantly higher than the levels in control animals. Albumin mRNA levels were unaffected by hypophysectomy. These results are in opposition to those which we had anticipated. Based on previously published data, we had thought that physiologic deprivation of corticosteriods would lead to decreased levels of fibrinogen. We propose that these results are related to the negative feedback that corticosteroids have on Hepatocyte Stimulating Factor (HSF) production through a tightly controlled feedback circuit. To investigate the role of corticosteriods in fibrinogen gene regulation, we have conducted experiments with primary hepatocytes in culture and rat FAZA cells (continuous hepatoma cell line). There is a 4 to 5 fold increase in fibrinogen production when these cells are treated with HSF but no change when these cells are treated with dexamethasone alone. However, there is a marked additional increase in the production of fibrinogen with the combination of dexamethasone and HSF. Data gathered through kinetic analysis of this synergistic interaction suggest that the maximum response to HSF requires another gene product whose production is responsive to dexamethasone. Detailed analysis of the rate of transcription of thegamma fibrinogen gene, its processing and mRNA turnover suggests a specific role for this gene product in regulating fibrinogen synthesis. Characterization of this gene product will lead to greater understanding of the regulation of the Acute Phase Reactants.
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Reitsma, P. H., A. M. Riemens, R. M. Bertina et E. Briít. « PROMOTOR MUTATIONS IN A PATIENT WITH HAEMOPHILIA B LEYDEN ». Dans XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643870.
Texte intégralRésumé :
Haemophilia B Leyden is characterized by low levels of factor IX antigen and activity before the age of 15, whereas after puberty factor IX levels rise at a rate of about 4-5% per year. To date such a genetic variant of factor IX synthesis has been reported in two (probably related) Dutch families, in a Greek and in an American family of Armenian descent. Laboratory and clinical investigations indicate that the factor IX protein is normal but that the regulation of factor IX synthesis has come under the control of the steroid hormone testosterone. We have started to investigate the factor IX gene in a patient from a Dutch family in an attempt to explain the aberrant regulation.Southern blotting revealed no gross deletions or insertions in the factor IX gene. Therefore the promotor region of the factor IX gene was cloned and subjected to a detailed restriction enzyme analysis. This also did not indicate that significant DNA deletions or insertions had occurred. Subsequently we established the nucleotide sequence of the DNA surrounding the first exon which encompassed about 600 basepairs of the promotor region. Two deviations from previously published sequence data were recorded. Firstly, an A T change was noted in the presumed "tata" box region 20 basepairs upstream from the start site of mRNA synthesis. Secondly, at position −423 a T C change was found which lies 13 basepairs upstream from a potential alternative "tata" box.The point mutation at position −20 might well explain the failure of gene expression during the prepuberal stage of the disease. Whether the same point mutation also leads to the testosterone effects or that a second sequence variation is a prerequisite for this phenomenon remains to be established from studies on the promotor region in representatives of the Greek and American families. Eventually the introduction of chaemeric genes, containing the various promotor regions, into testosterone responsive cells should delineate the promotor sequences responsible for the variations in factor IX gene expression.
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Zhang, Liping, et Jian S. Dai. « Genome Reconfiguration of Metamorphic Manipulators Based on Lie Group Theory ». Dans ASME 2008 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2008. http://dx.doi.org/10.1115/detc2008-49906.
Texte intégralRésumé :
This paper investigates reconfiguration which was induced by topology change as a typical character of metamorphic mechanisms in a way analogous to the concept of genome varation in biological study. Genome is the full complement of genetic information that an organism inherits from its parents, espercially the set of genes they carry. Genome variation is to study the change and variation of this complement with genetic information and genes connectivity and is analogous to mechanisms reconfiguration of metamorphic mechanisms. Metamorphic mechanisms with reconfigurable topology are usually changing their configurations and varying mobility in accordance with different sub-working phase functions. The built-in spatial biological modules are for the first time compiled and introduced in this paper based on metamorphic building blocks in the form of metamorphic cells and associated inside break-down parts as the metamorphic genes for metamorphic bio-modeling as genome. The gene sequencing labels the genetic structure composition principle of the metamorphic manipulators. The bio-inspired mechanism configuration evolution is further introduced in this paper motivated by biological concept to metamorphic characteristics as different sub-phase working mechanisms gradually change and develop into different forms in a particular situation and over a period of time, as an evolutionary process of topological change that takes place over several motion phases during which a taxonomic group of organisms showing the change of their physical characteristics. Moreover, the proposed genetic structure composition principle in metamorphic manipulators leads to the development of module evolution and genetic operations based on the displacement subgroup algebraic properties of the Lie group theory. The topology transformations can further be simulated for configuration evolution and depicted with the genetic growth and degeneration in the living nature. Genome sequential reconfiguration for metamorphic manipulators promises to be mapped from degenerating the source generator to multiple sub-phase configurations. Evolution design illustrations are given to demonstrate the concept and principles.
Rapports d'organisations sur le sujet "Leader genes"
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Lifschitz, Eliezer, et Elliot Meyerowitz. The Relations between Cell Division and Cell Type Specification in Floral and Vegetative Meristems of Tomato and Arabidopsis. United States Department of Agriculture, février 1996. http://dx.doi.org/10.32747/1996.7613032.bard.
Texte intégralRésumé :
Meristems were the central issue of our project. Genes that are required for cell division, cell elongation, cell proliferation and cell fate were studied in the tomato system. The analysis of the dUTPase and threonine deaminase genes, along with the dissection of their regulatory regions is completed, while that of the RNR2 and PPO genes is at an advanced stage. All these genes were isolated in our laboratory. In addition, 8 different MADS box genes were studied in transgenic plants and their genetic relevances discovered. We have also shown that a given MADS box gene can modify the polarity of cell division without affecting the fate of the organ. In vivo interaction between two MADS box genes was demonstrated and the functional dependency of the tomato agamous gene on the TM5 gene product established. We have exploited the Knotted1 meristematic gene in conjunction with tomato leaf meristematic genes to show that simple and compound leaves and, for that matter, sepals and compound leaves, are formed by two different developmental programs. In this context we have also isolated and characterized the tomato Knotted1 gene (TKnl) and studied its expression pattern. A new program in which eight different meristematic genes in tomato will be studied emerged as a result of these studies. In essence, we have shown that it is possible to study and manipulate plant developmental systems using reverse genetic techniques and have provided a wealth of new molecular tools to interested colleagues working with tomato. Similarly, genes responsible for cell division, cell proliferation and cell fate were studied in Arabidopsis floral meristems. Among these genes are the TSO1, TSO2, HANABA TARANU and UNUSUAL FLORAL ORGANS genes, each affecting in its own way the number of pattern of cell divisions, and cell fate, in developing Arabodopsis flowers. In addition, new methods have been established for the assessment of the function of regulatory gene action in the different clonal layers of developing floral meristems.
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Granot, David, et Richard Amasino. Regulation of Senescence by Sugar Metabolism. United States Department of Agriculture, janvier 2003. http://dx.doi.org/10.32747/2003.7585189.bard.
Texte intégralRésumé :
Research objectives a. Analyze transgenic plants that undergo rapid senescence due to increased expression of hexokinase. b. Determine if hexokinase-induced senescence accelerates natural senescence using senescence specific promoters that drive expression of a reporter gene (GUS) and a cytokinin producing gene (IPT - isopentyl transferase). c. Isolate and analyze plant genes that suppress sugar-induced cell death (SICD) in yeast, genes that potentially are involved in programmed cell death and senescence in plants. Background to the topic Leaf senescence is a regulated process of programmed cell death (PCD) in which metabolites are recycled to other active parts of the plant. Senescence associated genes (SAGs) are expressed throughout leaf senescence. Sugar flux and metabolism is thought to playa fundamental regulatory role in senescence. We found that transgenic tomato plants with high hexokinase activity, the initial enzymatic step of sugar (hexose) metabolism, undergo rapid leaf senescence, directly correlated with hexokinase activity. These plants provide a unique opportunity to analyze the regulatory role of sugar metabolism in senescence, and its relation to cytokinin, a senescence-inhibiting hormone. In addition, we found that sugar induces programmed cells death of yeast cells in direct correlation to hexokinase activity. We proposed to use the sugar induced cell death (SICD) to isolate Arabidopsis genes that suppress SICD. Such genes could potentially be involved in senescence induced PCD in plants. Major conclusions The promoters of Arabidopsis senescence-associated genes, SAG12 and SAGI3, are expressed in senescing tomato leaves similar to their expression in Arabidopsis leaves, indicating that these promoters are good senescence markers for tomato plants. Increased hexokinase activity accelerated senescence and induced expression of pSAG12 and pSAG13 promoters in tomato plants, suggesting that sugar regulate natural senescence via hexokinase. Expression of IPT, a cytokinin producing gene, under pSAG12 and pSAG13 promoters, delayed senescence of tomato leaves. Yet, senescence accelerated by hexokinase was epistatic over cytokinin, indicating that sugar regulation of senescence is dominant over the senescence-inhibiting hormone. A gene designated SFP1, which is similar to the major super family monosaccharide transporters, is induced during leaf senescence in Arabidopsis and may be involved in sugar transport during senescence. Accordingly, adult leaves accumulate sugars that may accelerate hexokinase activity. Light status of the entire plant affects the senescence of individual leaves. When individual leaves are darkened, senescence is induced in the covered leaves. However, whole adult plant placed in darkness show delayed senescence. In a search for Arabidopsis genes that suppress SICD we isolated 8 cDNA clones which confer partial resistance to SICD. One of the clones encodes a vesicle associated membrane protein - VAMP. This is the first evidence that vesicle trafficking might be involved in cell death. Implications Increased hexokinase activity accelerates senescence. We hypothesized that, reduced hexokinase activity may delay senescence. Preliminary experiments using a hexokinase inhibitor support this possible implication. Currently we are analyzing various practical approaches to delay leaf senescence via hexokinase inhibition. .
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Ori, Naomi, et Mark Estelle. Specific mediators of auxin activity during tomato leaf and fruit development. United States Department of Agriculture, janvier 2012. http://dx.doi.org/10.32747/2012.7597921.bard.
Texte intégralRésumé :
The plant hormone auxin is involved in numerous developmental processes, including leaf and fruit development. The tomato (Solanumlycopersicum) gene ENTIRE (E) encodes an auxin-response inhibitor from the Aux/IAA family. While most loss-offunction mutations in Aux/IAA genes are similar to the wild type due to genetic redundancy, entire (e) mutants show specific effects on leaf and fruit development. e mutants have simple leaves, in contrast to the compound leaves of wild type tomatoes. In addition, e plants produce parthenocarpic fruits, in which fruit set occurs independently of fertilization. The aim of this research program was to utilize the e mutation to identify and characterize genes that mediate the specific effect of auxin in leaf and fruit development. The specific objectives of the project were to: 1. Characterize and map modifiers of the e leaf phenotype. 2. Characterize and map suppressors of the e fruit phenotype. 3. Dissect the developmental specificity of the E gene. 4. Examine the effect of fruit-overexpression of identified genes on fruit set and seed production. To identify mediators of auxin in leaf development, we mainly focused on one mutant, crawling elephant (crel, previously called t282), which showed substantial suppression of the e phenotype and other auxin-relatedphenotypes. We have identified the CREL gene as a homolog of the Arabidopsis VRN5 gene, involved in recruiting polycomb silencing complexes to specific targets. We showed that CREL affects auxin sensitivity in tomato. Suppressors of the e fruit phenotype have been further characterized and selected for more profound effects. Expression profiling by RNAseq was used to analyze the effect of e as well as crel on gene expression in leaves and fruits. This analysis has identified putative E and CREL targets. We have initiated studies to assess the role of some of these targets in flower and fruit development. The research has identified potential mediators of auxin response in leaf, flower and fruit development.
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Mawassi, Munir, et Valerian Dolja. Role of RNA Silencing Suppression in the Pathogenicity and Host Specificity of the Grapevine Virus A. United States Department of Agriculture, janvier 2010. http://dx.doi.org/10.32747/2010.7592114.bard.
Texte intégralRésumé :
RNA silencing is a defense mechanism that functions against virus infection and involves sequence-specific degradation of viral RNA. Diverse RNA and DNA viruses of plants encode RNA silencing suppressors (RSSs), which, in addition to their role in viral counterdefense, were implicated in the efficient accumulation of viral RNAs, virus transport, pathogenesis, and determination of the virus host range. Despite rapidly growing understanding of the mechanisms of RNA silencing suppression, systematic analysis of the roles played by diverse RSSs in virus biology and pathology is yet to be completed. Our research was aimed at conducting such analysis for two grapevine viruses, Grapevine virus A (GVA) and Grapevine leafroll-associated virus-2 (GLRaV- 2). Our major achievements on the previous cycle of BARD funding are as follows. 1. GVA and GLRaV-2 were engineered into efficient gene expression and silencing vectors for grapevine. The efficient techniques for grapevine infection resulting in systemic expression or silencing of the recombinant genes were developed. Therefore, GVA and GLRaV-2 were rendered into powerful tools of grapevine virology and functional genomics. 2. The GVA and GLRaV-2 RSSs, p10 and p24, respectively, were identified, and their roles in viral pathogenesis were determined. In particular, we found that p10 functions in suppression and pathogenesis are genetically separable. 3. We revealed that p10 is a self-interactive protein that is targeted to the nucleus. In contrast, p24 mechanism involves binding small interfering RNAs in the cytoplasm. We have also demonstrated that p10 is relatively weak, whereas p24 is extremely strong enhancer of the viral agroinfection. 4. We found that, in addition to the dedicated RSSs, GVA and GLRaV-2 counterdefenses involve ORF1 product and leader proteases, respectively. 5. We have teamed up with Dr. Koonin and Dr. Falnes groups to study the evolution and function of the AlkB domain presents in GVA and many other plant viruses. It was demonstrated that viral AlkBs are RNA-specific demethylases thus providing critical support for the biological relevance of the novel process of AlkB-mediated RNA repair.
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Dubcovsky, Jorge, Tzion Fahima, Ann Blechl et Phillip San Miguel. Validation of a candidate gene for increased grain protein content in wheat. United States Department of Agriculture, janvier 2007. http://dx.doi.org/10.32747/2007.7695857.bard.
Texte intégralRésumé :
High Grain Protein Content (GPC) of wheat is important for improved nutritional value and industrial quality. However, selection for this trait is limited by our poor understanding of the genes involved in the accumulation of protein in the grain. A gene with a large effect on GPC was detected on the short arm of chromosome 6B in a Triticum turgidum ssp. dicoccoides accession from Israel (DIC, hereafter). During the previous BARD project we constructed a half-million clones Bacterial Artificial Chromosome (BAC) library of tetraploid wheat including the high GPC allele from DIC and mapped the GPC-B1 locus within a 0.3-cM interval. Our long-term goal is to provide a better understanding of the genes controlling grain protein content in wheat. The specific objectives of the current project were to: (1) complete the positional cloning of the GPC-B1 candidate gene; (2) characterize the allelic variation and (3) expression profile of the candidate gene; and (4) validate this gene by using a transgenic RNAi approach to reduce the GPC transcript levels. To achieve these goals we constructed a 245-kb physical map of the GPC-B1 region. Tetraploid and hexaploid wheat lines carrying this 245-kb DIC segment showed delayed senescence and increased GPC and grain micronutrients. The complete sequencing of this region revealed five genes. A high-resolution genetic map, based on approximately 9,000 gametes and new molecular markers enabled us to delimit the GPC-B1 locus to a 7.4-kb region. Complete linkage of the 7.4-kb region with earlier senescence and increase in GPC, Zn, and Fe concentrations in the grain suggested that GPC-B1 is a single gene with multiple pleiotropic effects. The annotation of this 7.4-kb region identified a single gene, encoding a NAC transcription factor, designated as NAM-B1. Allelic variation studies demonstrated that the ancestral wild wheat allele encodes a functional NAC transcription factor whereas modern wheat varieties carry a non-functional NAM-B1 allele. Quantitative PCR showed that transcript levels for the multiple NAMhomologues were low in flag leaves prior to anthesis, after which their levels increased significantly towards grain maturity. Reduction in RNA levels of the multiple NAMhomologues by RNA interference delayed senescence by over three weeks and reduced wheat grain protein, Zn, and Fe content by over 30%. In the transgenic RNAi plants, residual N, Zn and Fe in the dry leaves was significantly higher than in the control plants, confirming a more efficient nutrient remobilization in the presence of higher levels of GPC. The multiple pleiotropic effects of NAM genes suggest a central role for these genes as transcriptional regulators of multiple processes during leaf senescence, including nutrient remobilization to the developing grain. The cloning of GPC-B1 provides a direct link between the regulation of senescence and nutrient remobilization and an entry point to characterize the genes regulating these two processes. This may contribute to their more efficient manipulation in crops and translate into food with enhanced nutritional value. The characterization of the GPC-B1 gene will have a significant impact on wheat production in many regions of the world and will open the door for the identification of additional genes involved in the accumulation of protein in the grain.
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Lers, Amnon, E. Lomaniec, S. Burd, A. Khalchitski, L. Canetti et Pamela J. Green. Analysis of Senescence Inducible Ribonuclease in Tomato : Gene Regulation and Function. United States Department of Agriculture, février 2000. http://dx.doi.org/10.32747/2000.7570563.bard.
Texte intégralRésumé :
Natural leaf senescence has a negative influence on yield. Postharvest induced senescence contributes to the losses of quality in flowers, foliage, and vegetables. Strategies designed to control the senescence process in crop plants could therefore have great applied significance. Senescence is regulated by differential gene expression yet, functional characterization of the genes specifically induced and study of their expression control, is still in its infancy. Study of senescence-specific genes is required to allow identification of regulatory elements participating in senescence-induced expression and thus provide insights into the genetic regulation of senescence. A main feature of senescence is the hydrolysis of macromolecules by hydrolases of various types such as RNases and proteases. This study was aimed a analysis of senescence-inducible RNases in tomato with the following objectives: Isolation of senescence-inducible RNase cDNA clones; Expression analyses of RNase genes during senescence; Identification of sequences required for senescence-induced gene expression; Functional analyses of senescence-inducible RNases. We narrowed our aims somewhat to focus on the first three objectives because the budget we were awarded was reduced from that requested. We have expanded our research for identification senescence-related RNase/nuclease activities as we thought it will direct us to new RNase/nuclease genes. We have also carried out research in Arabidopsis and parsley, which enabled us to draw mire general conclusions. We completed the first and second objectives and have made considerable progress on the remaining two. We have defined growth conditions suitable for this research and defined the physiological and biochemical parameters characteristic to the advance of leaf senescence. In tomato and arabidopsis we have focused on natural leaf senescence. Parsley was used mainly for study of postharvest senescence in detached leaves. We have identified a 41-kD a tomato nuclease, LeNUCI, specifically induced during senescence which can degrade both RNA and DNA. This activity could be induced by ethylene in young leaves and was subjected to detailed analysis, which enabled its classification as Nuclease I enzyme. LeNUCI may be involved in nucleic acid metabolism during tomato leaf senescence. In parsley senescing leaves we identified 2 main senescence-related nuclease activities of 41 and 39-kDa. These activities were induced in both naturally or artificially senescing leaves, could degrade both DNA and RNA and were very similar in their characteristics to the LeNUCI. Two senescence-induced RNase cDNAs were cloned from tomato. One RNase cDNA was identical to the tomato LX RNase while the second corresponded to the LE RNase. Both were demonstrated before to be induced following phosphate starvation of tomato cell culture but nothing was known about their expression or function in plants. LX gene expression was much more senescence specific and ethylene could activate it in detached young leaves. LE gene expression, which could be transiently induced by wounding, appeared to be activated by abscisic acid. We suggest that the LX RNase has a role in RNA catabolism in the final stage of senescence, and LE may be a defense-related protein. Transgenic plants were generated for altering LX gene expression. No major visible alterations in the phenotype were observed so far. Detailed analysis of senescence in these plants is performed currently. The LX promoter was cloned and its analysis is performed currently for identification of senescence-specific regulatory elements. In Arabidopsis we have identified and characterized a senescence-associated nuclease 1 gene, BFN1, which is highly expressed during leaf and stem senescence. BFN1, is the first example of a senescence- associated gene encoding a nuclease I enzyme as well as the first nuclease I cloned and characterized from Arabidopsis. Our progress should provide excellent tools for the continued analysis of regulation and function of senescence-inducible ribonucleases and nucleases in plants. The cloned genes can be used in reverse genetic approaches, already initiated, which can yield a more direct evidence for the function of these enzymes. Another contribution of this research will be in respect to the molecular mechanism, which controls senescence. We had already initiated in this project and will continue to identify and characterize regulatory elements involved in senescence-specific expression of the genes isolated in this work.
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Lers, Amnon, et Gan Susheng. Study of the regulatory mechanism involved in dark-induced Postharvest leaf senescence. United States Department of Agriculture, janvier 2009. http://dx.doi.org/10.32747/2009.7591734.bard.
Texte intégralRésumé :
Postharvest leaf senescence contributes to quality losses in flowers and leafy vegetables. The general goal of this research project was to investigate the regulatory mechanisms involved in dark-induced leaf senescence. The regulatory system involved in senescence induction and control is highly complex and possibly involves a network of senescence promoting pathways responsible for activation of the senescence-associated genes. Pathways involving different internal signals and environmental factors may have distinctive importance in different leaf senescence systems. Darkness is known to have a role in enhancement of postharvest leaf senescence and for getting an insight into its regulatory mechanism/s we have applied molecular genetics and functional genomics approaches. The original objectives were: 1. Identification of dark-induced SAGs in Arabidopsis using enhancer/promoter trap lines and microarray approaches; 2. Molecular and functional characterization of the identified genes by analyzing their expression and examining the phenotypes in related knockout mutant plants; 3. Initial studies of promoter sequences for selected early dark-induced SAGs. Since genomic studies of senescence, with emphasis on dark-induced senescence, were early-on published which included information on potential regulatory genes we decided to use this new information. This is instead of using the uncharacterized enhancer/promoter trap lines as originally planned. We have also focused on specific relevant genes identified in the two laboratories. Based on the available genomic analyses of leaf senescence 10 candidate genes hypothesized to have a regulatory role in dark-induced senescence were subjected to both expression as well as functional analyses. For most of these genes senescence-specific regulation was confirmed, however, functional analyses using knock-out mutants indicated no consequence to senescence progression. The transcription factor WARK75 was found to be specifically expressed during natural and dark-induced leaf senescence. Functional analysis demonstrated that in detached leaves senescence under darkness was significantly delayed while no phenotypic consequences could be observed on growth and development, including no effect on natural leaf senescence,. Thus, WARKY75 is suggested to have a role in dark-induced senescence, but not in natural senescence. Another regulatory gene identified to have a role in senescence is MKK9 encoding for a Mitogen-Activated Protein Kinase Kinase 9 which is upregulated during senescence in harvested leaves as well as in naturally senescing leaves. MKK9 can specifically phosphorylate another kinase, MPK6. Both knockouts of MKK9 and MPK6 displayed a significantly senescence delay in harvested leaves and possibly function as a phosphorelay that regulates senescence. To our knowledge, this is the first report that clearly demonstrates the involvement of a MAP kinase pathway in senescence. This research not only revealed a new signal transduction pathway, but more important provided significant insights into the regulatory mechanisms underlying senescence in harvested leaves. In an additional line of research we have employed the promoter of the senescence-induced BFN1 gene as a handle for identifying components of the regulatory mechanism. This gene was shown to be activated during darkinduced senescence of detached leaves, as well as natural senescence. This was shown by following protein accumulation and promoter activity which demonstrated that this promoter is activated during dark-induced senescence. Analysis of the promoter established that, at least some of the regulatory sequences reside in an 80 bps long fragment of the promoter. Overall, progress was made in identification of components with a role in dark-induced senescence in this project. Further studies should be done in order to better understand the function of these components and develop approaches for modulating the progress of senescence in crop plants for the benefit of agriculture.
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Dolja, Valerian V., Amit Gal-On et Victor Gaba. Suppression of Potyvirus Infection by a Closterovirus Protein. United States Department of Agriculture, mars 2002. http://dx.doi.org/10.32747/2002.7580682.bard.
Texte intégralRésumé :
The plant virus family Polyviridae is the largest and most destructive of all plant viruses. Despite the continuous effort to develop resistant plant varieties, there is a desperate need for novel approaches conferring wide-range potyvirus resistance. Based on experiments with the tobacco etch potyvirus (TEV)-derived gene expression vector, we suggested approach for screening of the candidate resistance genes. This approach relies on insertion of the genes into a virus vector and evaluation of the phenotypes of the resulting recombinant viruses. The genes which suppress infection by the recombinant virus are selected as candidates for engineering transgenic resistance. Our analysis of the TEV variants expressing proteins of the beet yellows closterovirus (BYV) revealed that one of those, the leader proteinase (L-Pro), strongly and specifically interfered with the hybrid TEV infection. Since closterovirus L-Pro is evolutionary related to potyviral helper component-proteinase (HC-Pro), we suggested that the L-Pro interfered with HC-Pro function via a trans-dominant inhibitory effect. Based on these findings, we proposed to test two major hypotheses. First, we suggested that L-Pro-mediated suppression of potyvirus infection is a general phenomenon effective against a range of potyviruses. The second hypothesis stated that the suppression effect can be reproduced in transgenic plants expressing L-Pro, and can be utilized for generation of resistance to potyviruses. In accord with these hypotheses, we developed two original objectives of our proposal: A) to determine the range of the closterovirus-derived suppression of potyviral infection, and B) to try and utilize the L-Pro-mediated suppression for the development of transgenic resistance to potyviruses. In the first phase of the project, we have developed all major tools and technologies required for successful completion of the proposed research. These included TEV and ZYMV vectors engineered to express several closteroviral L-Pro variants, and generation of the large collection of transgenic plants. To our satisfaction, characterization of the infection phenotypes exhibited by chimeric TEV and ZYMV variants confirmed our first hypothesis. For instance, similar to TEV-L- Pro(BYV) chimera, ZYMV-L-Pro(LIYV) chimera was debilitated in its systemic spread. In contrast, ZYMV-GUS chimera (positive control) was competent in establishing vigorous systemic infection. These and other results with chimeric viruses indicated that several closteroviral proteinases inhibit long-distance movement of the potyviruses upon co-expression in infected plants. In order to complete the second objective, we have generated ~90 tobacco lines transformed with closteroviral L-Pro variants, as well as ~100 lines transformed with BYV Hsp70-homolog (Hsp70h; a negative control). The presence and expression of the trans gene in each line was initially confirmed using RT-PCR and RNA preparations isolated from plants. However, since detection of the trans gene-specific RNA can not guarantee production of the corresponding protein, we have also generated L-Pro- and Hsp70h-specific antisera using corresponding synthetic peptides. These antisera allowed us to confirm that the transgenic plant lines produced detectable, although highly variable levels of the closterovirus antigens. In a final phase of the project, we tested susceptibility of the transgenic lines to TEV infection. To this end, we determined that the minimal dilution of the TEV inoculum that is still capable of infecting 100% of nontransgenic plants was 1:20, and used 10 plants per line (in total, ~2,000 plants). Unfortunately, none of the lines exhibited statistically significant reduction in susceptibility. Although discouraging, this outcome prompted us to expand our experimental plan and conduct additional experiments. Our aim was to test if closteroviral proteinases are capable of functioning in trans. We have developed agroinfection protocol for BYV, and tested if co- expression of the L-Pro is capable of rescuing corresponding null-mutant. The clear-cut, negative results of these experiments demonstrated that L-Pro acts only in cis, thus explaining the lack of resistance in our transgenic plants. We have also characterized a collection of the L-Pro alanine- scanning mutants and found direct genetic evidence of the requirement for L-Pro in virus systemic spread. To conclude, our research supported by BARD confirmed one but not another of our original hypotheses. Moreover, it provided an important insight into functional specialization of the viral proteinases and generated set of tools and data with which we will be able to address the molecular mechanisms by which these proteins provide a variety of critical functions during virus life cycle.
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Michelmore, Richard, Eviatar Nevo, Abraham Korol et Tzion Fahima. Genetic Diversity at Resistance Gene Clusters in Wild Populations of Lactuca. United States Department of Agriculture, février 2000. http://dx.doi.org/10.32747/2000.7573075.bard.
Texte intégralRésumé :
Genetic resistance is often the least expensive, most effective, and ecologically-sound method of disease control. It is becoming apparent that plant genomes contain large numbers of disease resistance genes. However, the numbers of different resistance specificities within a genepool and the genetic mechanisms generating diversity are poorly understood. Our objectives were to characterize diversity in clusters of resistance genes in wild progenitors of cultivated lettuce in Israel and California in comparison to diversity within cultivated lettuce, and to determine the extent of gene flow, recombination, and genetic instability in generating variation within clusters of resistance genes. Genetic diversity of resistance genes was analyzed in wild and cultivated germplasm using molecular markers derived from lettuce resistance gene sequences of the NBS-LRR type that mapped to the major cluster if resistance genes in lettuce (Sicard et al. 1999). Three molecular markers, one microsatellite marker and two SCAR markers that amplified LRR- encoding regions, were developed from sequences of resistance gene homologs at the Dm3 cluster (RGC2s) in lettuce. Variation for these markers was assessed in germplasm including 74 genotypes of cultivated lettuce, L. saliva and 71 accessions of the three wild Lactuca spp., L. serriola, L. saligna and L. virosa that represent the major species in the sexually accessible genepool for lettuce. Diversity was also studied within and between natural populations of L. serriola from Israel and California. Large numbers of haplotypes were detected indicating the presence of numerous resistance genes in wild species. We documented a variety of genetic events occurring at clusters of resistance genes for the second objective (Sicard et al., 1999; Woo el al., in prep; Kuang et al., in prepb). The diversity of resistance genes in haplotypes provided evidence for gene duplication and unequal crossing over during the evolution of this cluster of resistance genes. Comparison of nine resistance genes in cv. Diana identified 22 gene conversion and five intergenic recombinations. We cloned and sequenced a 700 bp region from the middle of RGC2 genes from six genotypes, two each from L. saliva, L. serriola, and L. saligna . We have identified over 60 unique RGC2 sequences. Phylogenetic analysis surprisingly demonstrated much greater similarity between than within genotypes. This led to the realization that resistance genes are evolving much slower than had previously been assumed and to a new model as to how resistance genes are evolving (Michelmore and Meyers, 1998). The genetic structure of L. serriola was studied using 319 AFLP markers (Kuang et al., in prepa). Forty-one populations from Turkey, Armenia, Israel, and California as well as seven European countries were examined. AFLP marker data showed that the Turkish and Armenian populations were the most polymorphic populations and the European populations were the least. The Davis, CA population, a recent post-Columbian colonization, showed medium genetic diversity and was genetically close to the Turkish populations. Our results suggest that Turkey - Armenia may be the center of origin and diversity of L. serriola and may therefore have the greatest diversity of resistance genes. Our characterization of the diversity of resistance genes and the genetic mechanisms generating it will allow informed exploration, in situ and ex situ conservation, and utilization of germplasm resources for disease control. The results of this project provide the basis for our future research work, which will lead to a detailed understanding of the evolution of resistance genes in plants.
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Cohen, Yuval, Christopher A. Cullis et Uri Lavi. Molecular Analyses of Soma-clonal Variation in Date Palm and Banana for Early Identification and Control of Off-types Generation. United States Department of Agriculture, octobre 2010. http://dx.doi.org/10.32747/2010.7592124.bard.
Texte intégralRésumé :
Date palm (Phoenix dactylifera L.) is the major fruit tree grown in arid areas in the Middle East and North Africa. In the last century, dates were introduced to new regions including the USA. Date palms are traditionally propagated through offshoots. Expansion of modern date palm groves led to the development of Tissue Culture propagation methods that generate a large number of homogenous plants, have no seasonal effect on plant source and provide tools to fight the expansion of date pests and diseases. The disadvantage of this procedure is the occurrence of off-type trees which differ from the original cultivar. In the present project we focused on two of the most common date palm off-types: (1) trees with reduced fruit setting, in which most of the flowers turn into three-carpel parthenocarpic fruits. In a severe form, multi-carpel flowers and fruitlets (with up to six or eight carpels instead of the normal three-carpel flowers) are also formed. (2) dwarf trees, having fewer and shorter leaves, very short trunk and are not bearing fruits at their expected age, compared to the normal trees. Similar off-types occur in other crop species propagated by tissue culture, like banana (mainly dwarf plants) or oil palm (with a common 'Mantled' phenotype with reduced fruit setting and occurrence of supernumerary carpels). Some off-types can only be detected several years after planting in the fields. Therefore, efficient methods for prevention of the generation of off-types, as well as methods for their detection and early removal, are required for date palms, as well as for other tissue culture propagated crops. This research is aimed at the understanding of the mechanisms by which off-types are generated, and developing markers for their early identification. Several molecular and genomic approaches were applied. Using Methylation Sensitive AFLP and bisulfite sequencing, we detected changes in DNA methylation patterns occurring in off-types. We isolated and compared the sequence and expression of candidate genes, genes related to vegetative growth and dwarfism and genes related to flower development. While no sequence variation were detected, changes in gene expression, associated with the severity of the "fruit set" phenotype were detected in two genes - PdDEF (Ortholog of rice SPW1, and AP3 B type MADS box gene), and PdDIF (a defensin gene, highly homologous to the oil palm gene EGAD). We applied transcriptomic analyses, using high throughput sequencing, to identify genes differentially expressed in the "palm heart" (the apical meristem and the region of embryonic leaves) of dwarf vs. normal trees. Among the differentially expressed genes we identified genes related to hormonal biosynthesis, perception and regulation, genes related to cell expansion, and genes related to DNA methylation. Using Representation Difference Analyses, we detected changes in the genomes of off-type trees, mainly chloroplast-derived sequences that were incorporated in the nuclear genome and sequences of transposable elements. Sequences previously identified as differing between normal and off-type trees of oil palms or banana, successfully identified variation among date palm off-types, suggesting that these represent highly labile regions of monocot genomes. The data indicate that the date palm genome, similarly to genomes of other monocot crops as oil palm and banana, is quite unstable when cells pass through a cycle of tissue culture and regeneration. Changes in DNA sequences, translocation of DNA fragments and alteration of methylation patterns occur. Consequently, patterns of gene expression are changed, resulting in abnormal phenotypes. The data can be useful for future development of tools for early identification of off-type as well as for better understanding the phenomenon of somaclonal variation during propagation in vitro.