Journal articles: 'Leader genes'

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Orlando, Bruno, Luca Giacomelli, Massimiliano Ricci, Antonio Barone, and Ugo Covani. "Leader genes in osteogenesis: a theoretical study." Archives of Oral Biology 58, no. 1 (January 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, and Ludovico Sbordone. "The Association between Periodontitis and Human Colorectal Cancer: Genetic and Pathogenic Linkage." Life 10, no. 9 (September 18, 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, and Claudio Nicolini. "Bioinformatic Prediction of Leader Genes in Human Periodontitis." Journal of Periodontology 79, no. 10 (October 2008): 1974–83. http://dx.doi.org/10.1902/jop.2008.080062.

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Dossin, Fernando de Macedo, and Sergio Schenkman. "Actively Transcribing RNA Polymerase II Concentrates on Spliced Leader Genes in the Nucleus of Trypanosoma cruzi." Eukaryotic Cell 4, no. 5 (May 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, and Myeong-Sok Lee. "Transcriptional regulation of histidine biosynthesis genes in Corynebacterium glutamicum." Canadian Journal of Microbiology 56, no. 2 (February 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, and David Morse. "Fugacium Spliced Leader Genes Identified from Stranded RNA-Seq Datasets." Microorganisms 7, no. 6 (June 11, 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, and 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 (July 1, 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, and 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 (November 26, 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, and 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 (February 1, 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, and Gary Loughran. "Systematic analysis of the PTEN 5′ leader identifies a major AUU initiated proteoform." Open Biology 6, no. 5 (May 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.

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Pettitt, Jonathan, Neale Harrison, Ian Stansfield, Bernadette Connolly, and Berndt Müller. "The evolution of spliced leader trans-splicing in nematodes." Biochemical Society Transactions 38, no. 4 (July 26, 2010): 1125–30. http://dx.doi.org/10.1042/bst0381125.

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Spliced leader trans-splicing occurs in many primitive eukaryotes including nematodes. Most of our knowledge of trans-splicing in nematodes stems from the model organism Caenorhabditis elegans and relatives, and from work with Ascaris. Our investigation of spliced leader trans-splicing in distantly related Dorylaimia nematodes indicates that spliced-leader trans-splicing arose before the nematode phylum and suggests that the spliced leader RNA gene complements in extant nematodes have evolved from a common ancestor with a diverse set of spliced leader RNA genes.

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12

Sita, S. E. Donny, and N. A. Mohd Nor. "A Systematic Review on Leadership Styles in Small and Medium Enterprises." 12th GLOBAL CONFERENCE ON BUSINESS AND SOCIAL SCIENCES 12, no. 1 (October 8, 2021): 26. http://dx.doi.org/10.35609/gcbssproceeding.2021.12(26).

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Earlier notions of leadership opined that leadership can be found in one's genes that determine how an individual behaves and reacts to his/her surrounding (Bass, 1985). That is, a leader can still be detected in a group of people although nobody may be appointed to lead at the outset. In the past, an individual became a leader through inheritance of a rank or the throne in a country or in an institution. However, the temperament or characteristic of an individual determine whether one can lead or not. A leader acts as a conflict contributor, a resolver or peacemaker, and a punisher (King et al., 2009). Besides being dominant over the rest of the group members, a leader needs to influence the followers too with his/her leadership style. The leadership style of a leader depends on the attitude of him/her to influencing followers in the organisation. The modern era indicates that an uncertainty or complex situations are not uncommon. In a context of a small and medium enterprises (SMEs), turbulences arising in an enterprise require an effective leader to sustain a strong sense of opportunity for all followers. Such participation allows followers to share opinions, make better decisions and control the resources. In fact, followers and the leader cannot be separated. Likewise, leadership runs in tandem with development. Development occurs as leadership pushes it (Banyai, 2009). Hence, without proper leadership to lead the followers, it would be rather difficult to reach the mutual goals of the enterprise (Poskas & Messer, 2015). Also, a good leadership through guidance and effective communication enables followers to improve themselves. Hence, to conduct a relevant systematic review, the current paper is guided by the following main research question: how are leadership styles practiced among leaders in the context of small and medium enterprises? The focus of this paper is on the leaders of small and medium enterprises where followers are working together towards achieving the mutual goals of the enterprise. Keywords: leader; leadership style; PRISMA; small and medium enterprises; systematic literature review

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Brill, Jeanette, Tamara Hoffmann, Harald Putzer, and Erhard Bremer. "T-box-mediated control of the anabolic proline biosynthetic genes of Bacillus subtilis." Microbiology 157, no. 4 (April 1, 2011): 977–87. http://dx.doi.org/10.1099/mic.0.047357-0.

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Bacillus subtilis possesses interlinked routes for the synthesis of proline. The ProJ–ProA–ProH route is responsible for the production of proline as an osmoprotectant, and the ProB–ProA–ProI route provides proline for protein synthesis. We show here that the transcription of the anabolic proBA and proI genes is controlled in response to proline limitation via a T-box-mediated termination/antitermination regulatory mechanism, a tRNA-responsive riboswitch. Primer extension analysis revealed mRNA leader transcripts of 270 and 269 nt for the proBA and proI genes, respectively, both of which are synthesized from SigA-type promoters. These leader transcripts are predicted to fold into two mutually exclusive secondary mRNA structures, forming either a terminator or an antiterminator configuration. Northern blot analysis allowed the detection of both the leader and the full-length proBA and proI transcripts. Assessment of the level of the proBA transcripts revealed that the amount of the full-length mRNA species strongly increased in proline-starved cultures. Genetic studies with a proB–treA operon fusion reporter strain demonstrated that proBA transcription is sensitively tied to proline availability and is derepressed as soon as cellular starvation for proline sets in. Both the proBA and the proI leader sequences contain a CCU proline-specific specifier codon prone to interact with the corresponding uncharged proline-specific tRNA. By replacing the CCU proline specifier codon in the proBA T-box leader with UUC, a codon recognized by a Phe-specific tRNA, we were able to synthetically re-engineer the proline-specific control of proBA transcription to a control that was responsive to starvation for phenylalanine.

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Ross, Leorah H., Jonathan H. Freedman, and Charles S. Rubin. "Structure and Expression of Novel Spliced Leader RNA Genes inCaenorhabditis elegans." Journal of Biological Chemistry 270, no. 37 (September 15, 1995): 22066–75. http://dx.doi.org/10.1074/jbc.270.37.22066.

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STURM, NANCY R., DMITRI A. MASLOV, EDMUNDO C. GRISARD, and DAVID A. CAMPBELL. "Diplonema spp. Possess Spliced Leader RNA Genes Similar to the Kinetoplastida." Journal of Eukaryotic Microbiology 48, no. 3 (May 2001): 325–31. http://dx.doi.org/10.1111/j.1550-7408.2001.tb00321.x.

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Gu, Z., R. Harrod, E. J. Rogers, and P. S. Lovett. "Anti-peptidyl transferase leader peptides of attenuation-regulated chloramphenicol-resistance genes." Proceedings of the National Academy of Sciences 91, no. 12 (June 7, 1994): 5612–16. http://dx.doi.org/10.1073/pnas.91.12.5612.

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McCarthy-Burke, Cathleen, Zoe A. Taylor, and Gregory A. Buck. "Characterization of the spliced leader genes and transcripts in Trypanosoma cruzi." Gene 82, no. 1 (October 1989): 177–89. http://dx.doi.org/10.1016/0378-1119(89)90043-7.

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Cumsky, M. G., C. E. Trueblood, C. Ko, and R. O. Poyton. "Structural analysis of two genes encoding divergent forms of yeast cytochrome c oxidase subunit V." Molecular and Cellular Biology 7, no. 10 (October 1987): 3511–19. http://dx.doi.org/10.1128/mcb.7.10.3511-3519.1987.

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In Saccharomyces cerevisiae, subunit V of the inner mitochondrial membrane protein complex cytochrome c oxidase is encoded by two nonidentical genes, COX5a and COX5b. Both genes are present as single copies in S. cerevisiae and in several other Saccharomyces species. Nucleotide sequencing studies with the S. cerevisiae COX5 genes reveal that they encode proteins of 153 and 151 amino acids, respectively. Overall, the coding sequences of COX5a and COX5b have nucleotide and protein homologies of 67 and 66%, respectively. They are saturated for nucleotide substitutions that result in a synonomous codon, indicating a long divergence time between these two genes. Nucleotide sequences flanking the COX5a and COX5b coding regions exhibit no significant homology. The COX5a protein, pre-subunit Va, contains a 20-amino-acid leader peptide, whereas the COX5b protein, pre-subunit Vb, contains a 17-amino-acid leader peptide. These two leader peptides exhibit only 45% homology in the primary sequence, but have similar predicted secondary structures. By analyzing the RNA transcripts from both genes we have found that COX5a is a contiguous gene but that COX5b contains an intron. Surprisingly, the COX5b intron interrupts the AUG codon that initiates translation of the pre-subunit Vb polypeptide and contains a 5' donor splice sequence that differs from that normally found in yeast introns.

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Cumsky, M. G., C. E. Trueblood, C. Ko, and R. O. Poyton. "Structural analysis of two genes encoding divergent forms of yeast cytochrome c oxidase subunit V." Molecular and Cellular Biology 7, no. 10 (October 1987): 3511–19. http://dx.doi.org/10.1128/mcb.7.10.3511.

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In Saccharomyces cerevisiae, subunit V of the inner mitochondrial membrane protein complex cytochrome c oxidase is encoded by two nonidentical genes, COX5a and COX5b. Both genes are present as single copies in S. cerevisiae and in several other Saccharomyces species. Nucleotide sequencing studies with the S. cerevisiae COX5 genes reveal that they encode proteins of 153 and 151 amino acids, respectively. Overall, the coding sequences of COX5a and COX5b have nucleotide and protein homologies of 67 and 66%, respectively. They are saturated for nucleotide substitutions that result in a synonomous codon, indicating a long divergence time between these two genes. Nucleotide sequences flanking the COX5a and COX5b coding regions exhibit no significant homology. The COX5a protein, pre-subunit Va, contains a 20-amino-acid leader peptide, whereas the COX5b protein, pre-subunit Vb, contains a 17-amino-acid leader peptide. These two leader peptides exhibit only 45% homology in the primary sequence, but have similar predicted secondary structures. By analyzing the RNA transcripts from both genes we have found that COX5a is a contiguous gene but that COX5b contains an intron. Surprisingly, the COX5b intron interrupts the AUG codon that initiates translation of the pre-subunit Vb polypeptide and contains a 5' donor splice sequence that differs from that normally found in yeast introns.

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Cummins, C., and P. Anderson. "Regulatory myosin light-chain genes of Caenorhabditis elegans." Molecular and Cellular Biology 8, no. 12 (December 1988): 5339–49. http://dx.doi.org/10.1128/mcb.8.12.5339-5349.1988.

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We have cloned and analyzed the Caenorhabditis elegans regulatory myosin light-chain genes. C. elegans contains two such genes, which we have designated mlc-1 and mlc-2. The two genes are separated by 2.6 kilobases and are divergently transcribed. We determined the complete nucleotide sequences of both mlc-1 and mlc-2. A single, conservative amino acid substitution distinguishes the sequences of the two proteins. The C. elegans proteins are strongly homologous to regulatory myosin light chains of Drosophila melanogaster and vertebrates and weakly homologous to a superfamily of eucaryotic calcium-binding proteins. Both mlc-1 and mlc-2 encode abundant mRNAs. We mapped the 5' termini of these transcripts by using primer extension sequencing of mRNA templates. mlc-1 mRNAs initiate within conserved hexanucleotides at two different positions, located at -28 and -38 relative to the start of translation. The 5' terminus of mlc-2 mRNA is not encoded in the 4.8-kilobase genomic region upstream of mlc-2. Rather, mlc-2 mRNA contains at its 5' end a short, untranslated leader sequence that is identical to the trans-spliced leader sequence of three C. elegans actin genes.

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Cummins, C., and P. Anderson. "Regulatory myosin light-chain genes of Caenorhabditis elegans." Molecular and Cellular Biology 8, no. 12 (December 1988): 5339–49. http://dx.doi.org/10.1128/mcb.8.12.5339.

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We have cloned and analyzed the Caenorhabditis elegans regulatory myosin light-chain genes. C. elegans contains two such genes, which we have designated mlc-1 and mlc-2. The two genes are separated by 2.6 kilobases and are divergently transcribed. We determined the complete nucleotide sequences of both mlc-1 and mlc-2. A single, conservative amino acid substitution distinguishes the sequences of the two proteins. The C. elegans proteins are strongly homologous to regulatory myosin light chains of Drosophila melanogaster and vertebrates and weakly homologous to a superfamily of eucaryotic calcium-binding proteins. Both mlc-1 and mlc-2 encode abundant mRNAs. We mapped the 5' termini of these transcripts by using primer extension sequencing of mRNA templates. mlc-1 mRNAs initiate within conserved hexanucleotides at two different positions, located at -28 and -38 relative to the start of translation. The 5' terminus of mlc-2 mRNA is not encoded in the 4.8-kilobase genomic region upstream of mlc-2. Rather, mlc-2 mRNA contains at its 5' end a short, untranslated leader sequence that is identical to the trans-spliced leader sequence of three C. elegans actin genes.

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Moffat, J. G., W. P. Tate, and P. S. Lovett. "The leader peptides of attenuation-regulated chloramphenicol resistance genes inhibit translational termination." Journal of Bacteriology 176, no. 22 (1994): 7115–17. http://dx.doi.org/10.1128/jb.176.22.7115-7117.1994.

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Lenardo, M. J., D. M. Dorfman, and J. E. Donelson. "The spliced leader sequence of Trypanosoma brucei has a potential role as a cap donor structure." Molecular and Cellular Biology 5, no. 9 (September 1985): 2487–90. http://dx.doi.org/10.1128/mcb.5.9.2487-2490.1985.

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Trypanosoma brucei brucei and other trypanosomatid species are unique among eucaryotes because transcription of their protein-coding genes is discontinuous. The 5' ends of their mRNAs consist of an identical 35-nucleotide spliced leader which is encoded at a separate locus from that for the body of the protein-coding transcript. We show here that the spliced leader transcript contains a 5' cap structure and suggest that at least one function of the spliced leader sequence is to provide a cap structure to trypanosome mRNAs.

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Lenardo, M. J., D. M. Dorfman, and J. E. Donelson. "The spliced leader sequence of Trypanosoma brucei has a potential role as a cap donor structure." Molecular and Cellular Biology 5, no. 9 (September 1985): 2487–90. http://dx.doi.org/10.1128/mcb.5.9.2487.

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Trypanosoma brucei brucei and other trypanosomatid species are unique among eucaryotes because transcription of their protein-coding genes is discontinuous. The 5' ends of their mRNAs consist of an identical 35-nucleotide spliced leader which is encoded at a separate locus from that for the body of the protein-coding transcript. We show here that the spliced leader transcript contains a 5' cap structure and suggest that at least one function of the spliced leader sequence is to provide a cap structure to trypanosome mRNAs.

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Delhaye, Sophie, Vincent van Pesch, and Thomas Michiels. "The Leader Protein of Theiler's Virus Interferes with Nucleocytoplasmic Trafficking of Cellular Proteins." Journal of Virology 78, no. 8 (April 15, 2004): 4357–62. http://dx.doi.org/10.1128/jvi.78.8.4357-4362.2004.

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ABSTRACT The leader protein of Theiler's virus was previously shown to block the production of alpha/beta interferon by infected cells. Here, we observed that expression of the leader protein in infected cells triggered subcellular redistribution of a nucleus-target green fluorescent protein. It enhanced redistribution of the nuclear polypyrimidine tract-binding protein but had no influence on the localization of the nuclear splicing factor SC-35. The leader protein also interfered with trafficking of the cytoplasmic interferon regulatory factor 3, a factor critical for transcriptional activation of alpha/beta interferon genes.

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Melior, Hendrik, and Elena Evguenieva-Hackenberg. "Trans-agierende Attenuator-RNA und Leaderpeptid in Bakterien." BIOspektrum 27, no. 2 (March 2021): 127–30. http://dx.doi.org/10.1007/s12268-021-1545-0.

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AbstractBacterial transcription attenuators are a source of small RNAs (sRNAs) and leader peptides, for which no own functions were known. However, the attenuator sRNA of the tryptophan (Trp) biosynthesis operon regulates gene expression in trans according to the Trp-availability. Moreover, the cognate leader peptide adopted Trp-independent functions. It builds antibiotic-dependent ribonucleoprotein complexes (ARNPs) for sRNA reprogramming and regulation of ribosomal and multiresistance genes.

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Hook-Barnard, India G., Timothy J. Brickman, and Mark A. McIntosh. "Identification of an AU-rich Translational Enhancer within the Escherichia coli fepB Leader RNA." Journal of Bacteriology 189, no. 11 (March 30, 2007): 4028–37. http://dx.doi.org/10.1128/jb.01924-06.

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ABSTRACT The fepB gene encodes a periplasmic binding protein that is essential for the uptake of ferric enterobactin by Escherichia coli. Its transcription is regulated in response to iron levels by the Fur repressor. The fepB transcript includes a 217-nucleotide leader sequence with several features suggestive of posttranscriptional regulation. To investigate the fepB leader for its contribution to fepB expression, defined deletions and substitution mutations in the leader were characterized using fepB-phoA translational fusions. The fepB leader was found to be necessary for maximal fepB expression, primarily due to the influence of an AU-rich translational enhancer (TE) located 5′ to the Shine-Dalgarno sequence. Deletions or substitutions within the TE sequence decreased fepB-phoA expression fivefold. RNase protection and in vitro transcription-translation assays demonstrated that the TE augmented translational efficiency, as well as RNA levels. Moreover, primer extension inhibition assays showed that the TE increases ribosome binding. In contrast to the enhancing effect of the TE, the natural fepB GUG start codon decreased ribosome binding and reduced fepB expression 2.5-fold compared with the results obtained with leaders bearing an AUG initiation codon. Thus, the TE-GUG organization in fepB results in an intermediate level of expression compared to the level with AUG, with or without the TE. Furthermore, we found that the TE-GUG sequence is conserved among the eight gram-negative strains examined that have fepB genes, suggesting that this organization may provide a selective advantage.

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Aksoy, Serap. "Spliced leader RNA and 5S rRNA genes in Herpetomonas spp. are genetically linked." Nucleic Acids Research 20, no. 4 (1992): 913. http://dx.doi.org/10.1093/nar/20.4.913.

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Keller, M., L. H. Tessier, R. L. Chan, J. H. Weil, and P. lmbault. "InEuglena, spliced-leader RNA (SL-RNA) and 5S rRNA genes are tandemly repeated." Nucleic Acids Research 20, no. 7 (1992): 1711–15. http://dx.doi.org/10.1093/nar/20.7.1711.

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Zhang, H., D. A. Campbell, N. R. Sturm, and S. Lin. "Dinoflagellate Spliced Leader RNA Genes Display a Variety of Sequences and Genomic Arrangements." Molecular Biology and Evolution 26, no. 8 (April 22, 2009): 1757–71. http://dx.doi.org/10.1093/molbev/msp083.

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Nunes, Luiz R., Marta M. G. Teixeira, Erney Plessman Camargo, and Gregory A. Buck. "Sequence and structural characterization of the spliced leader genes and transcripts in Phytomonas." Molecular and Biochemical Parasitology 74, no. 2 (November 1995): 233–37. http://dx.doi.org/10.1016/0166-6851(95)02496-4.

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Baughman, Gail, and Stephen H. Howell. "Cauliflower mosaic virus 35 S RNA leader region inhibits translation of downstream genes." Virology 167, no. 1 (November 1988): 125–35. http://dx.doi.org/10.1016/0042-6822(88)90061-x.

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Haanes-Fritz, Elizabeth, Werner Kraus, Vickers Burdett, James B. Dale, Edwin H. Beachey, and Patrick Cleary. "Comparison of the leader sequences of four group A streptococcal M protein genes." Nucleic Acids Research 16, no. 10 (1988): 4667–77. http://dx.doi.org/10.1093/nar/16.10.4667.

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Costanzo, M. C., and T. D. Fox. "Product of Saccharomyces cerevisiae nuclear gene PET494 activates translation of a specific mitochondrial mRNA." Molecular and Cellular Biology 6, no. 11 (November 1986): 3694–703. http://dx.doi.org/10.1128/mcb.6.11.3694-3703.1986.

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The product of Saccharomyces cerevisiae nuclear gene PET494 is known to be required for a posttranscriptional step in the accumulation of one mitochondrial gene product, subunit III of cytochrome c oxidase (coxIII). Here we show that the PET494 protein probably acts in mitochondria by demonstrating that both a PET494-beta-galactosidase fusion protein and unmodified PET494 are specifically associated with mitochondria. To define the PET494 site of action, we isolated mutations that suppress a pet494 deletion. These mutations were rearrangements of the mitochondrial gene oxi2 that encodes coxIII. The suppressor oxi2 genes had acquired the 5'-flanking sequences of other mitochondrial genes and gave rise to oxi2 transcripts carrying the 5'-untranslated leaders of their mRNAs. These results demonstrate that in wild-type cells PET494 specifically promotes coxIII translation, probably by interacting with the 5'-untranslated leader of the oxi2 mRNA.

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Costanzo, M. C., and T. D. Fox. "Product of Saccharomyces cerevisiae nuclear gene PET494 activates translation of a specific mitochondrial mRNA." Molecular and Cellular Biology 6, no. 11 (November 1986): 3694–703. http://dx.doi.org/10.1128/mcb.6.11.3694.

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The product of Saccharomyces cerevisiae nuclear gene PET494 is known to be required for a posttranscriptional step in the accumulation of one mitochondrial gene product, subunit III of cytochrome c oxidase (coxIII). Here we show that the PET494 protein probably acts in mitochondria by demonstrating that both a PET494-beta-galactosidase fusion protein and unmodified PET494 are specifically associated with mitochondria. To define the PET494 site of action, we isolated mutations that suppress a pet494 deletion. These mutations were rearrangements of the mitochondrial gene oxi2 that encodes coxIII. The suppressor oxi2 genes had acquired the 5'-flanking sequences of other mitochondrial genes and gave rise to oxi2 transcripts carrying the 5'-untranslated leaders of their mRNAs. These results demonstrate that in wild-type cells PET494 specifically promotes coxIII translation, probably by interacting with the 5'-untranslated leader of the oxi2 mRNA.

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Ofoghi, H., N. Moazami, and I. Ivanov. "Comparison of Tobacco Etch Virus and Tobacco Mosaic Virus Enhancers for Expression of Human Calcitonin Gene in Transgenic Potato Plant." Key Engineering Materials 277-279 (January 2005): 7–11. http://dx.doi.org/10.4028/www.scientific.net/kem.277-279.7.

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The translational enhancement of the 5′-leader sequence of the tobacco mosaic virus (TMV) and tobacco etch viral 5′-leader sequence (TEV) was compared in relation to the expression of the human calcitonin (hCT) gene in transgenic potato plants. The synthetic human calcitonin tetrameric genes were cloned under the control of the 35S Cauliflower mosaic virus (CaMV)promoter linked to the TMV or TEV leader sequences. The resulting constructs were cloned into the binary vector Bin19 and potato minituber discs transformed using an agrobacterium strain. The expression of the hCT gene was studied by mRNA-DNA hybridization, a RT-PCR, ELISA and RIA. The results showed that the TMV omega element increased the yield of the expressed recombinant protein two to three-fold in comparison with the TEV leader sequence.

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Bailey, K. L., H. Harding, and P. Hucl. "Four interspecific germplasm lines (302–1, 302–3, 302–5, 302–20) of spring wheat with resistance to common root rot (Cochliobolus sativus) derived from Aegilops ovata." Canadian Journal of Plant Science 75, no. 3 (July 1, 1995): 693–94. http://dx.doi.org/10.4141/cjps95-116.

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Germplasm resistant to common root rot was developed from crossing Aegilops ovata with Triticum aestivum, using Chinese Spring ph 1b genetic stock and the cultivar Leader. The germplasm lines had yellow flour pigment and a longer mixing time and lower SDS sedimentation volume, falling number, and mixograph peak height than Leader. Yet, for most agronomic and quality traits, the germplasm was similar to that of Leader and Neepawa. Seed was classed as CWRS. This germplasm represents a different source of genes for resistance to common root rot than currently available in red spring wheat cultivars or breeding lines. Key words: Common root rot, resistance, Aegilops ovata, Triticum aestivum, germplasm

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Yu, Tianliang, Aneesha Acharya, Nikos Mattheos, Simin Li, Dirk Ziebolz, Gerhard Schmalz, Rainer Haak, Jana Schmidt, and Yu Sun. "Molecular mechanisms linking peri-implantitis and type 2 diabetes mellitus revealed by transcriptomic analysis." PeerJ 7 (June 21, 2019): e7124. http://dx.doi.org/10.7717/peerj.7124.

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Aims To explore molecular mechanisms that link peri-implantitis and type 2 diabetes mellitus (T2DM) by bioinformatic analysis of publicly available experimental transcriptomic data. Materials and methods Gene expression data from peri-implantitis were downloaded from the Gene Expression Omnibus database, integrated and differentially expressed genes (DEGs) in peri-implantitis were identified. Next, experimentally validated and computationally predicted genes related to T2DM were downloaded from the DisGeNET database. Protein–protein interaction network (PPI) pairs of DEGs related to peri-implantitis and T2DM related genes were constructed, “hub” genes and overlapping DEG were determined. Functional enrichment analysis was used to identify significant shared biological processes and signaling pathways. The PPI networks were subjected to cluster and specific class analysis for identifying “leader” genes. Module network analysis of the merged PPI network identified common or cross-talk genes connecting the two networks. Results A total of 92 DEGs overlapped between peri-implantitis and T2DM datasets. Three hub genes (IL-6, NFKB1, and PIK3CG) had the highest degree in PPI networks of both peri-implantitis and T2DM. Three leader genes (PSMD10, SOS1, WASF3), eight cross-talk genes (PSMD10, PSMD6, EIF2S1, GSTP1, DNAJC3, SEC61A1, MAPT, and NME1), and one signaling pathway (IL-17 signaling) emerged as peri-implantitis and T2DM linkage mechanisms. Conclusions Exploration of available transcriptomic datasets revealed IL-6, NFKB1, and PIK3CG expression along with the IL-17 signaling pathway as top candidate molecular linkage mechanisms between peri-implantitis and T2DM.

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Fields, Christopher J., and Robert L. Switzer. "Regulation of pyr Gene Expression in Mycobacterium smegmatis by PyrR-Dependent Translational Repression." Journal of Bacteriology 189, no. 17 (June 29, 2007): 6236–45. http://dx.doi.org/10.1128/jb.00803-07.

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ABSTRACT Regulation of pyrimidine biosynthetic (pyr) genes by a transcription attenuation mechanism that is mediated by the PyrR mRNA-binding regulatory protein has been demonstrated for numerous gram-positive bacteria. Mycobacterial genomes specify pyrR genes and contain obvious PyrR-binding sequences in the initially transcribed regions of their pyr operons, but transcription antiterminator and attenuation terminator sequences are absent from their pyr 5′ leader regions. This work demonstrates that repression of pyr operon expression in Mycobacterium smegmatis by exogenous uracil requires the pyrR gene and the pyr leader RNA sequence for binding of PyrR. Plasmids containing the M. smegmatis pyr promoter-leader region translationally fused to lacZ also displayed pyrR-dependent repression, but transcriptional fusions of the same sequences to a lacZ gene that retained the lacZ ribosome-binding site were not regulated by PyrR plus uracil. We propose that PyrR regulates pyr expression in M. smegmatis, other mycobacteria, and probably in numerous other bacteria by a translational repression mechanism in which nucleotide-regulated binding of PyrR occludes the first ribosome-binding site of the pyr operon.

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Johansen, Lars Engholm, Per Nygaard, Catharina Lassen, Yvonne Agersø, and Hans H. Saxild. "Definition of a Second Bacillus subtilis pur Regulon Comprising the pur and xpt-pbuX Operons plus pbuG, nupG (yxjA), and pbuE (ydhL)." Journal of Bacteriology 185, no. 17 (September 1, 2003): 5200–5209. http://dx.doi.org/10.1128/jb.185.17.5200-5209.2003.

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ABSTRACT In Bacillus subtilis expression of genes or operons encoding enzymes and other proteins involved in purine synthesis is affected by purine bases and nucleosides in the growth medium. The genes belonging to the PurR regulon (purR, purA, glyA, guaC, pbuO, pbuG, and the pur, yqhZ-folD, and xpt-pbuX operons) are controlled by the PurR repressor, which inhibits transcription initiation. Other genes are regulated by a less-well-described transcription termination mechanism that responds to the presence of hypoxanthine and guanine. The pur operon and the xpt-pbuX operon, which were studied here, are regulated by both mechanisms. We isolated two mutants resistant to 2-fluoroadenine in which the pur operon and the xpt-pbuX operon are expressed at increased levels in a PurR-independent manner. The mutations were caused by deletions that disrupted a potential transcription terminator structure located immediately upstream of the ydhL gene. The 5′ part of the ydhL leader region contained a 63-nucleotide (nt) sequence very similar to the 5′ ends of the leaders of the pur and xpt-pbuX operons. Transcripts of these regions may form a common tandem stem-loop secondary structure. Two additional genes with potential leader regions containing the 63-nt sequence are pbuG, encoding a hypoxanthine-guanine transporter, and yxjA, which was shown to encode a purine nucleoside transporter and is renamed nupG. Transcriptional lacZ fusions and mutations in the 63-nt sequence encoding the possible secondary structures provided evidence that expression of the pur and xpt-pbuX operons and expression of the ydhL, nupG, and pbuG genes are regulated by a common mechanism. The new pur regulon is designated the XptR regulon. Except for ydhL, the operons and genes were negatively regulated by hypoxanthine and guanine. ydhL was positively regulated. The derived amino acid sequence encoded by ydhL (now called pbuE) is similar to the amino acid sequences of metabolite efflux pumps. When overexpressed, PbuE lowers the sensitivity to purine analogs. Indirect evidence indicated that PbuE decreases the size of the internal pool of hypoxanthine. This explains why the hypoxanthine- and guanine-regulated genes are expressed at elevated levels in a mutant that overexpresses pbuE.

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Ferguson, Kimberly C., and Joel H. Rothman. "Alterations in the Conserved SL1trans-Spliced Leader of Caenorhabditis elegansDemonstrate Flexibility in Length and Sequence Requirements In Vivo." Molecular and Cellular Biology 19, no. 3 (March 1, 1999): 1892–900. http://dx.doi.org/10.1128/mcb.19.3.1892.

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ABSTRACT Approximately 70% of mRNAs in Caenorhabditis elegansare trans spliced to conserved 21- to 23-nucleotide leader RNAs. While the function of SL1, the major C. elegans trans-spliced leader, is unknown, SL1 RNA, which contains this leader, is essential for embryogenesis. Efforts to characterize in vivo requirements of the SL1 leader sequence have been severely constrained by the essential role of the corresponding DNA sequences in SL1 RNA transcription. We devised a heterologous expression system that circumvents this problem, making it possible to probe the length and sequence requirements of the SL1 leader without interfering with its transcription. We report that expression of SL1 from a U2 snRNA promoter rescues mutants lacking the SL1-encoding genes and that the essential embryonic function of SL1 is retained when approximately one-third of the leader sequence and/or the length of the leader is significantly altered. In contrast, although all mutant SL1 RNAs were well expressed, more severe alterations eliminate this essential embryonic function. The one non-rescuing mutant leader tested was never detected on messages, demonstrating that part of the leader sequence is essential for trans splicing in vivo. Thus, in spite of the high degree of SL1 sequence conservation, its length, primary sequence, and composition are not critical parameters of its essential embryonic function. However, particular nucleotides in the leader are essential for the in vivo function of the SL1 RNA, perhaps for its assembly into a functional snRNP or for the trans-splicing reaction.

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Baer, R., A. Forster, I. Lavenir, and T. H. Rabbitts. "Immunoglobulin VH genes are transcribed by T cells in association with a new 5' exon." Journal of Experimental Medicine 167, no. 6 (June 1, 1988): 2011–16. http://dx.doi.org/10.1084/jem.167.6.2011.

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We previously detected mRNAs in a number of human T cell lines with a probe from within the Ig VH gene locus. We now show these mRNAs consist of Ig VH genes expressed in T cells. In one human T cell line, two RNA species have been studied and found to come from transcripts of unrearranged VH segments in which the leader exon, normally associated with VH transcripts in B cells, is replaced by a novel 5' exon (ET) not encoding a hydrophobic leader peptide. In genomic DNA, this new ET exon is adjacent to a pseudo-VH gene that has not been observed in mature mRNA. This implies that RNA splicing controls association of the new exon with the expressed VH segments. Hence, VH transcription does indeed occur in T cells, but is qualitatively different from that in B cells.

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Horn, Nikki, Antonio Fernández, Helen M. Dodd, Michael J. Gasson, and Juan M. Rodríguez. "Nisin-Controlled Production of Pediocin PA-1 and Colicin V in Nisin- and Non-Nisin-Producing Lactococcus lactis Strains." Applied and Environmental Microbiology 70, no. 8 (August 2004): 5030–32. http://dx.doi.org/10.1128/aem.70.8.5030-5032.2004.

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ABSTRACT The introduction of chimeric genes encoding the fusion leader of lactococcin A-propediocin PA-1 or procolicin V under the control of the inducible nisA promoter and the lactococcin A-dedicated secretion genes (lcnCD) into Lactococcus lactis strains, including a nisin producer, expressing the two component regulator NisRK led to the production or pediocin PA-1 or colicin V, respectively.

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Weber, J. S., J. Berry, T. Manser, and J. L. Claflin. "Mutations in Ig V(D)J genes are distributed asymmetrically and independently of the position of V(D)J." Journal of Immunology 153, no. 8 (October 15, 1994): 3594–602. http://dx.doi.org/10.4049/jimmunol.153.8.3594.

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Abstract To study the distribution of somatic mutations in the DNA flanking the 5' side of rearranged Ig V genes, the 5' region of 14 to 21 mutant forms of three different V(D)J were sequenced. These were compared with a fourth V(D)J for which the flanking sequences of 10 mutant forms are known. The leader intron of these four V genes varied from 82 to 365 nucleotides in length. Analysis of the data showed that: 1) The mutation frequency is distributed asymmetrically with respect to the V(D)J exon with skewing in the 3' direction. 2) The distribution of mutations 5' of V(D)J seems to be related to the size of the leader intron. The significance of these findings for models of hypermutation is discussed.

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Grundy, F. J., S. C. Lehman, and T. M. Henkin. "The L box regulon: Lysine sensing by leader RNAs of bacterial lysine biosynthesis genes." Proceedings of the National Academy of Sciences 100, no. 21 (October 1, 2003): 12057–62. http://dx.doi.org/10.1073/pnas.2133705100.

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Aksoy, Serap. "A Family of Target Site-Specific Retrotransposons Interrupts Spliced Leader RNA Genes in Trypanosomatids." Journal of Parasitology 79, no. 5 (October 1993): 645. http://dx.doi.org/10.2307/3283595.

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Roditi, Isabel. "Trypanosoma vivax: linkage of the mini-exon (spliced leader) and 5S ribosomal RNA genes." Nucleic Acids Research 20, no. 8 (1992): 1995. http://dx.doi.org/10.1093/nar/20.8.1995.

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Deffaud, Clarence, and Jean-Luc Darlix. "Characterization of an Internal Ribosomal Entry Segment in the 5′ Leader of Murine Leukemia Virus envRNA." Journal of Virology 74, no. 2 (January 15, 2000): 846–50. http://dx.doi.org/10.1128/jvi.74.2.846-850.2000.

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ABSTRACT The 5′ untranslated region, also called the leader, of oncoretroviruses and lentiviruses is long and is formed of several structured domains critically important in virus replication. The 5′ leader of murine leukemia virus (MLV) RNA contains an internal ribosomal entry segment (IRES) which promotes synthesis of Gag and glyco-Gag polyprotein precursors. In the present study we investigated the translational features of the 5′ leader of MLV subgenomic RNA (env RNA) encoding the Env polyprotein precursor. When theenv leader was inserted between two genes, such aslacZ and the neomycin resistance cassette, in a dicistronic vector, it allowed IRES-dependent translation of the 3′ cistron in the rabbit reticulocyte lysate system and in murine cells. The drug rapamycin and the foot-and-mouth disease virus L protease, known to inhibit cap-dependent translation, caused an enhancement of the translation driven by the env leader sequence, consistent with an IRES activity promoting Env expression. Analysis of several deletion mutants led us to localize the minimal env IRES between the splice junction and the env AUG start codon.

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Zaporojets, Dmitry, Sarah French, and Catherine L. Squires. "Products Transcribed from Rearranged rrn Genes of Escherichia coli Can Assemble To Form Functional Ribosomes." Journal of Bacteriology 185, no. 23 (December 1, 2003): 6921–27. http://dx.doi.org/10.1128/jb.185.23.6921-6927.2003.

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ABSTRACT To examine the flexibility of rRNA operons with respect to fundamental organization, transcription, processing, and assembly of ribosomes, operon variations were introduced by a plasmid into an Escherichia coli strain that has deletions of all chromosomal copies of rRNA genes. In the reconstructed operons, a Salmonella intervening sequence (IVS) from 23S helix 45 was introduced into the E. coli 23S gene at the same position. Three different constructs of the E. coli 16S gene were then placed wholly within the IVS sequence, and the 16S gene was deleted from its normal position. The resulting plasmids thus had the normal operon promoters and the leader region followed by the 5′ one-third of the 23S gene, the entire 16S gene within the IVS, the last two-thirds of the 23S gene, and the normal end of the operon. The three constructs differed in the amount of 16S leader and spacer regions they contained. Only two of the three constructs, those with redundant leader and spacer antiterminator signals, resulted in viable cultures of the rrn deletion strain. Electron micrographs of the variant operon suggest that the 23S rRNA is made in two separate parts which then must form subassemblies before assembling into a functional 50S subunit. Cells containing only the reshuffled genes were debilitated in their growth properties and ribosome contents. The fact that such out of the ordinary manipulation of rRNA sequences in E. coli is possible paves the way for detailed analysis of ribosome assembly and evolution.

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Bang*, Haejeen, Sungil Kim, Daniel Leskovar, and Stephen King. "Differential Expression of Carotenoid Biosynthesis Genes among Different Colored Flesh in Watermelons [Citrullus lanatus (Thunb)]." HortScience 39, no. 4 (July 2004): 869E—870. http://dx.doi.org/10.21273/hortsci.39.4.869e.

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Carotenoids are plant compounds that serve a variety of essential functions in the plant and have also been found to have several health-promoting activities in humans. Carotenoids found in watermelon (Citrullus lanatus) flesh are responsible for the various colors such as red, yellow and orange. Previous inheritance studies of flesh color revealed that six genes were involved in color determination. The relationship and interaction of these genes suggests that some color-determining genes may be the result of mutations on the structural genes encoding enzymes in the carotenoid biosynthesis pathway. In this study we were able to isolate and sequence six genes encoding enzymes involved in the carotenoid biosynthetic pathway, and determine their expression in different colored watermelon fruit. The cDNA was synthesized from total RNA using RACE (Rapid Amplification of cDNA ends) kit (SMART RACE cDNA Amplification Kit; Clontech, Palo Alto, Calif.). Degenerate primers were designed based on published homologous genes from other species and were used to isolate gene fragments and full-length cDNAs of phytoene synthase, phytoene desaturase, _-carotene desaturase, β-cyclase, β-carotene hydroxylase and zeaxanthin expoxidase. RT-PCR was carried out to examine any differential expression of cloned genes in white, yellow, orange and red-fleshed watermelon. All cloned enzyme-encoding genes were expressed regardless of flesh colors. These results indicate that carotenoid biosynthesis may be regulated at the post-transcriptional level. One interesting feature supports this hypothesis. In case of β-cyclase, a 229-bp leader intron was identified, and an unspliced mRNA with this leader intron existed dominantly in cDNA pool of all samples.

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Journal articles on the topic 'Leader genes'

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