Academic literature on the topic 'Chloroplast genome studies'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the lists of relevant articles, books, theses, conference reports, and other scholarly sources on the topic 'Chloroplast genome studies.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Journal articles on the topic "Chloroplast genome studies"
1
Ahmad, Niaz, Muhammad Aamer Mehmood, and Sana Malik. "Recombinant Protein Production in Microalgae: Emerging Trends." Protein & Peptide Letters 27, no. 2 (January 6, 2020): 105–10. http://dx.doi.org/10.2174/0929866526666191014124855.
Full textAbstract:
: In recent years, microalgae have emerged as an alternative platform for large-scale production of recombinant proteins for different commercial applications. As a production platform, it has several advantages, including rapid growth, easily scale up and ability to grow with or without the external carbon source. Genetic transformation of several species has been established. Of these, Chlamydomonas reinhardtii has become significantly attractive for its potential to express foreign proteins inexpensively. All its three genomes – nuclear, mitochondrial and chloroplastic – have been sequenced. As a result, a wealth of information about its genetic machinery, protein expression mechanism (transcription, translation and post-translational modifications) is available. Over the years, various molecular tools have been developed for the manipulation of all these genomes. Various studies show that the transformation of the chloroplast genome has several advantages over nuclear transformation from the biopharming point of view. According to a recent survey, over 100 recombinant proteins have been expressed in algal chloroplasts. However, the expression levels achieved in the algal chloroplast genome are generally lower compared to the chloroplasts of higher plants. Work is therefore needed to make the algal chloroplast transformation commercially competitive. In this review, we discuss some examples from the algal research, which could play their role in making algal chloroplast commercially successful.
2
Sato, Naoki. "Are Cyanobacteria an Ancestor of Chloroplasts or Just One of the Gene Donors for Plants and Algae?" Genes 12, no. 6 (May 27, 2021): 823. http://dx.doi.org/10.3390/genes12060823.
Full textAbstract:
Chloroplasts of plants and algae are currently believed to originate from a cyanobacterial endosymbiont, mainly based on the shared proteins involved in the oxygenic photosynthesis and gene expression system. The phylogenetic relationship between the chloroplast and cyanobacterial genomes was important evidence for the notion that chloroplasts originated from cyanobacterial endosymbiosis. However, studies in the post-genomic era revealed that various substances (glycolipids, peptidoglycan, etc.) shared by cyanobacteria and chloroplasts are synthesized by different pathways or phylogenetically unrelated enzymes. Membranes and genomes are essential components of a cell (or an organelle), but the origins of these turned out to be different. Besides, phylogenetic trees of chloroplast-encoded genes suggest an alternative possibility that chloroplast genes could be acquired from at least three different lineages of cyanobacteria. We have to seriously examine that the chloroplast genome might be chimeric due to various independent gene flows from cyanobacteria. Chloroplast formation could be more complex than a single event of cyanobacterial endosymbiosis. I present the “host-directed chloroplast formation” hypothesis, in which the eukaryotic host cell that had acquired glycolipid synthesis genes as an adaptation to phosphate limitation facilitated chloroplast formation by providing glycolipid-based membranes (pre-adaptation). The origins of the membranes and the genome could be different, and the origin of the genome could be complex.
3
Mishra, Bagdevi, Bartosz Ulaszewski, Sebastian Ploch, Jaroslaw Burczyk, and Marco Thines. "A Circular Chloroplast Genome of Fagus sylvatica Reveals High Conservation between Two Individuals from Germany and One Individual from Poland and an Alternate Direction of the Small Single-Copy Region." Forests 12, no. 2 (February 4, 2021): 180. http://dx.doi.org/10.3390/f12020180.
Full textAbstract:
Chloroplasts are difficult to assemble because of the presence of large inverted repeats. At the same time, correct assemblies are important, as chloroplast loci are frequently used for biogeography and population genetics studies. In an attempt to elucidate the orientation of the single-copy regions and to find suitable loci for chloroplast single nucleotide polymorphism (SNP)-based studies, circular chloroplast sequences for the ultra-centenary reference individual of European Beech (Fagus sylvatica), Bhaga, and an additional Polish individual (named Jamy) was obtained based on hybrid assemblies. The chloroplast genome of Bhaga was 158,458 bp, and that of Jamy was 158,462 bp long. Using long-read mapping on the configuration inferred in this study and the one suggested in a previous study, we found an inverted orientation of the small single-copy region. The chloroplast genome of Bhaga and of the individual from Poland both have only two mismatches as well as three and two indels as compared to the previously published genome, respectively. The low divergence suggests low seed dispersal but high pollen dispersal. However, once chloroplast genomes become available from Pleistocene refugia, where a high degree of variation has been reported, they might prove useful for tracing the migration history of Fagus sylvatica in the Holocene.
4
Temel, Melih, Yasin Kaymaz, Duygu Ateş, Abdullah Kahraman, and Muhammed Bahattin Tanyolaç. "The Complete Chloroplast Genome Sequence of Cicer bijugum, Genome Organization, and Comparison with Related Species." Current Genomics 23, no. 1 (January 2022): 50–65. http://dx.doi.org/10.2174/1389202923666220211113708.
Full textAbstract:
Background: Chickpea is one of the legumes that is very important for Turkey and is frequently preferred especially in human nourishment thanks to its rich nutritional content. Chloroplasts, which have their own genetic material, are organelles responsible for photosynthesis in plant cells and their genome contains non-trivial information about the molecular features and evolutionary process of plants. Objective: Current study aimed at revealing complete chloroplast genome sequence of one of the wild type Cicer species Cicer bijugum and comparing its genome with cultivated Cicer species Cicer arietinum by using bioinformatics analysis tools. There are no study about revealing chloroplast genome sequence of Cicer species except the cultivated one Cicer arietinum. Therefore, we targeted to reveal the complete chloroplast genome sequence of wild type Cicer species Cicer bijugum and compare the chloroplast genome of Cicer bijugum with the cultivated one Cicer arietinum. Methods: In this study, we sequenced the whole chloroplast genome of Cicer bijugum, one of the wild types of chickpea species, with the help Next Generation Sequencing platform and compared it with the chloroplast genome of the cultivated chickpea species, Cicer arietinum by using online bioinformatics analysis tools. Results: We determined the size of the chloroplast genome of C. bijugum as 124,804 bp and found that C. bijugum did not contain an inverted repeat region in its chloroplast genome. Comparative analysis of the C. bijugum chloroplast genome uncovered thirteen hotspot regions (psbA, matK, rpoB, rpoC1, rpoC2, psbI, psbK, accD, rps19, ycf2, ycf1, rps15 and ndhF) and seven of them (matK, accD, rps19, ycf1, ycf2, rps15 and ndhF) could potentially be used as strong molecular markers for species identification. It has been determined that C. bijugum was phylogenetically closer to cultivated chickpea as compared to the other species. Conclusion: It is aimed that the data obtained from this study, which is the first study in which whole chloroplast genomes of wild chickpea species were sequenced, will guide researchers in future molecular, evolutionary and genetic engineering studies with chickpea species.
5
Zhang, Dachuan, Jiahao Wang, Liang Xu, Yanping Xing, Tingting Zhang, Shengnan Li, Yanyun Yang, Guihua Bao, Wuliji Ao, and Tingguo Kang. "Characteristic and Phylogenetic Analysis of the Complete Chloroplast Genomes of Three Medicinal Plants of Schisandraceae." BioMed Research International 2020 (October 16, 2020): 1–12. http://dx.doi.org/10.1155/2020/3536761.
Full textAbstract:
Schisandra chinensis, which has a high development value, has long been used as medicine. Its mature fruits (called Wuweizi in Chinese) have long been used in the famous traditional Chinese medicine (TCM) recorded in the “Chinese Pharmacopoeia.” Chloroplasts (CP) are the highly conserved primitive organelles in plants, which can serve as the foundation for plant classification and identification. This study introduced the structures of the CP genomes of three Schisandraceae species and analyzed their phylogenetic relationships. Comparative analyses on the three complete chloroplast genomes can provide us with useful knowledge to identify the three plants. In this study, approximately 5 g fresh leaves were harvested for chloroplast DNA isolation according to the improved extraction method. A total of three chloroplast DNAs were extracted. Afterwards, the chloroplast genomes were reconstructed using denovo combined with reference-guided assemblies. General characteristics of the chloroplast genome and genome comparison with three Schisandraceae species was analyzed by corresponding software. The total sizes of complete chloroplast genomes of S. chinensis, S. sphenanthera, and Kadsura coccinea were 146875 bp, 146842 bp, and 145399 bp, respectively. Altogether, 124 genes were annotated, including 82 protein-coding genes, 34 tRNAs, and 8 rRNAs of all 3 species. In SSR analysis, only S. chinensis was annotated to hexanucleotides. Moreover, comparative analysis of chloroplast Schisandraceae genome sequences revealed that the gene order and gene content were slightly different among Schisandraceae species. Finally, phylogenetic trees were reconstructed, based on the genome-wide SNPs of 38 species. The method can be used to identify and differentially analyze Schisandraceae plants and offer useful information for phylogenetics as well as further studies on traditional medicinal plants.
6
Ding, Yanqiang, Yang Fang, Ling Guo, Zhidan Li, Kaize He, Yun Zhao, and Hai Zhao. "Phylogenic study of Lemnoideae (duckweeds) through complete chloroplast genomes for eight accessions." PeerJ 5 (December 22, 2017): e4186. http://dx.doi.org/10.7717/peerj.4186.
Full textAbstract:
Background Phylogenetic relationship within different genera of Lemnoideae, a kind of small aquatic monocotyledonous plants, was not well resolved, using either morphological characters or traditional markers. Given that rich genetic information in chloroplast genome makes them particularly useful for phylogenetic studies, we used chloroplast genomes to clarify the phylogeny within Lemnoideae. Methods DNAs were sequenced with next-generation sequencing. The duckweeds chloroplast genomes were indirectly filtered from the total DNA data, or directly obtained from chloroplast DNA data. To test the reliability of assembling the chloroplast genome based on the filtration of the total DNA, two methods were used to assemble the chloroplast genome of Landoltia punctata strain ZH0202. A phylogenetic tree was built on the basis of the whole chloroplast genome sequences using MrBayes v.3.2.6 and PhyML 3.0. Results Eight complete duckweeds chloroplast genomes were assembled, with lengths ranging from 165,775 bp to 171,152 bp, and each contains 80 protein-coding sequences, four rRNAs, 30 tRNAs and two pseudogenes. The identity of L. punctata strain ZH0202 chloroplast genomes assembled through two methods was 100%, and their sequences and lengths were completely identical. The chloroplast genome comparison demonstrated that the differences in chloroplast genome sizes among the Lemnoideae primarily resulted from variation in non-coding regions, especially from repeat sequence variation. The phylogenetic analysis demonstrated that the different genera of Lemnoideae are derived from each other in the following order: Spirodela, Landoltia, Lemna, Wolffiella, and Wolffia. Discussion This study demonstrates potential of whole chloroplast genome DNA as an effective option for phylogenetic studies of Lemnoideae. It also showed the possibility of using chloroplast DNA data to elucidate those phylogenies which were not yet solved well by traditional methods even in plants other than duckweeds.
7
KIM, Mi-Hee, Suhyeon PARK, Junho LEE, Jinwook BAEK, Jongsun PARK, and Gun Woong LEE. "The complete chloroplast genome of Glycyrrhiza uralensis Fisch. isolated in Korea (Fabaceae)." Korean Journal of Plant Taxonomy 51, no. 4 (December 31, 2021): 353–62. http://dx.doi.org/10.11110/kjpt.2021.51.4.353.
Full textAbstract:
The chloroplast genome of Glycyrrhiza uralensis Fisch was sequenced to investigate intraspecific variations on the chloroplast genome. Its length is 127,689 bp long (34.3% GC ratio) with atypical structure of chloroplast genome, which is congruent to those of Glycyrrhiza genus. It includes 110 genes (76 protein-coding genes, four rRNAs, and 30 tRNAs). Intronic region of ndhA presented the highest nucleotide diversity based on the six G. uralenesis chloroplast genomes. A total of 150 single nucleotide polymorphisms and 10 insertion and deletion (INDEL) regions were identified from the six G. uralensis chloroplast genomes. Phylogenetic trees show that the six chloroplast genomes of G. uralensis formed the two clades, requiring additional studies to understand it.
8
Huang, Kerui, Ping Mo, Aihua Deng, Peng Xie, and Yun Wang. "Differences in the Chloroplast Genome and Its Regulatory Network among Cathaya argyrophylla Populations from Different Locations in China." Genes 13, no. 11 (October 27, 2022): 1963. http://dx.doi.org/10.3390/genes13111963.
Full textAbstract:
Cathaya argyrophylla Chun et Kuang is a severely endangered, tertiary relict plant unique to China whose high physiological sensitivity to the environment, including photosensitivity, is likely closely related to its endangered status; however, the exact mechanism responsible has remained unknown due to the rarity of the plant and the difficulties involved in performing physiological studies on the molecular level. In this study, the chloroplast genomes of six C. argyrophylla populations sampled from different locations in China were characterized and compared. In addition, a gene regulatory network of the polymorphic chloroplast genes responsible for regulating genes found elsewhere in the plant genome was constructed. The result of the genome characterization and comparison showed that the genome characteristics, the gene composition, and the gene sequence of the chloroplast genes varied by location, and the gene regulatory network showed that the differences in growth location may have led to variations in the protein-coding chloroplast gene via various metabolic processes. These findings provide new insights into the relationship between chloroplasts and the sensitive metabolism of C. argyrophylla and provide additional reference materials for the conservation of this endangered plant.
9
Zhang, Ying, Jing-Wen Zhang, Yong Yang, and Xin-Nian Li. "Structural and Comparative Analysis of the Complete Chloroplast Genome of a Mangrove Plant: Scyphiphora hydrophyllacea Gaertn. f. and Related Rubiaceae Species." Forests 10, no. 11 (November 8, 2019): 1000. http://dx.doi.org/10.3390/f10111000.
Full textAbstract:
Scyphiphora hydrophyllacea Gaertn. f. (Rubiaceae) is an endangered mangrove species found in China, and its only known location is in Hainan Island. Previous studies conducted on S. hydrophyllaceae have mainly focused on its location, biological characteristics, and medical effects. However, to date, there has been no published report regarding the genetics or genome of this endangered mangrove species. In this study, we developed valuable chloroplast genome-related molecular resources of S. hydrophyllaceae by comparing with it related Rubiaceae species. The chloroplast genome of S. hydrophyllaceae was found to be a circular molecule with a total size of 155,132 bp, and it is observed to have a quadripartite structure. The whole chloroplast genome contains 132 genes, of which 88 and 36 are protein-coding and transfer RNA genes, respectively; it also contains four ribosomal RNA genes with an overall GC content of 37.60%. A total of 52 microsatellites were detected in the S. hydrophyllacea chloroplast genome, and microsatellite marker detection identified A/T mononucleotides as majority simple sequence repeats in all nine Rubiaceae chloroplast genomes. Comparative analyses of these nine chloroplast genomes revealed variable regions, including matK, rps16, and atpF. All nine species shared 13 RNA-editing sites distributed across eight coding genes. Phylogenetic analyses based on the complete sequences of the chloroplast genomes revealed that the position of S. hydrophyllaceae is closer to the Coffeeae genus than to Cinchoneae, Naucleeae, Morindeae, and Rubieae in the Rubiaceae family. The genome information reported in this study could find further application in the evolution and population genetic studies, and it helps improve our understanding of the endangered mechanism and the development of conservation strategies of this endangered mangrove plant.
10
Zhai, Yufei, Xiaqing Yu, Junguo Zhou, Ji Li, Zhen Tian, Panqiao Wang, Ya Meng, et al. "Complete chloroplast genome sequencing and comparative analysis reveals changes to the chloroplast genome after allopolyploidization in Cucumis." Genome 64, no. 6 (June 2021): 627–38. http://dx.doi.org/10.1139/gen-2020-0134.
Full textAbstract:
Allopolyploids undergo “genomic shock” leading to significant genetic and epigenetic modifications. Previous studies have mainly focused on nuclear changes, while little is known about the inheritance and changes of organelle genome in allopolyploidization. The synthetic allotetraploid Cucumis ×hytivus, which is generated via hybridization between C. hystrix and C. sativus, is a useful model system for studying cytonuclear variation. Here, we report the chloroplast genome of allotetraploid C. ×hytivus and its diploid parents via sequencing and comparative analysis. The size of the obtained chloroplast genomes ranged from 154 673 to 155 760 bp, while their gene contents, gene orders, and GC contents were similar to each other. Comparative genome analysis supports chloroplast maternal inheritance. However, we identified 51 indels and 292 SNP genetic variants in the chloroplast genome of the allopolyploid C. ×hytivus relative to its female parent C. hystrix. Nine intergenic regions with rich variation were identified through comparative analysis of the chloroplast genomes within the subgenus Cucumis. The phylogenetic network based on the chloroplast genome sequences clarified the evolution and taxonomic position of the synthetic allotetraploid C. ×hytivus. The results of this study provide us with an insight into the changes of organelle genome after allopolyploidization, and a new understanding of the cytonuclear evolution.
Dissertations / Theses on the topic "Chloroplast genome studies"
1
Clark, Justine Ann. "Genetic variation in the chloroplast genome of a newly described Aster species, Chrysopsis delaneyi." [Tampa, Fla] : University of South Florida, 2006. http://purl.fcla.edu/usf/dc/et/SFE0001789.
Full textBooks on the topic "Chloroplast genome studies"
1
Kirchman, David L. Predation and protists. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198789406.003.0009.
Full textAbstract:
Protists are involved in many ecological roles in natural environments, including primary production, herbivory and carnivory, and parasitism. Microbial ecologists have been interested in these single-cell eukaryotes since Antonie van Leeuwenhoek saw them in his stool and scum from his teeth. This chapter focuses on the role of protozoa (purely heterotrophic protists) and other protists in grazing on other microbes. Heterotrophic nanoflagellates, 3–5 microns long, are the most important grazers of bacteria and small phytoplankton in aquatic environments. In soils, flagellates are also important, followed by naked amoebae, testate amoebae, and ciliates. Many of these protists feed on their prey by phagocytosis, in which the prey particle is engulfed into a food vacuole into which digestive enzymes are released. This mechanism of grazing explains many factors affecting grazing rates, such as prey numbers, size, and composition. Ingestion rates increase with prey numbers before reaching a maximum, similar to the Michaelis–Menten equation describing uptake as a function of substrate concentration. Protists generally eat prey that are about ten-fold smaller than they are. In addition to flagellates, ciliates and dinoflagellates are often important predators in the microbial world and are critical links between microbial food chains and larger organisms Many protists are capable of photosynthesis. In some cases, the predator benefits from photosynthesis carried out by engulfed, but undigested photosynthetic prey or its chloroplasts. Although much can be learnt from the morphology of large protists, small protists (<10 μm) often cannot be distinguished by morphology, and as seen several times in this book, many of the most abundant and presumably important protists are difficult to cultivate, necessitating the use of cultivation-independent methods analogous to those developed for prokaryotes. Instead of the 16S rRNA gene used for bacteria and archaea, the 18S rRNA gene is key for protists. Studies of this gene have uncovered high diversity in natural protist communities and, along with sequences of other genes, have upended models of eukaryote evolution. These studies indicate that the eukaryotic Tree of Life consists almost entirely of protists, with higher plants, fungi, and animals as mere branches.
Book chapters on the topic "Chloroplast genome studies"
1
Stupar, Milanko, and Slavica Stefanovic. "Studies on Mitoplastide Genome and Origin of Mitochondria and Chloroplast in Plants." In New Visions in Biological Science Vol. 6, 40–50. Book Publisher International (a part of SCIENCEDOMAIN International), 2021. http://dx.doi.org/10.9734/bpi/nvbs/v6/2109c.
Full text
2
Allendorf, Fred W., W. Chris Funk, Sally N. Aitken, Margaret Byrne, and Gordon Luikart. "Genetic Variation in Natural Populations." In Conservation and the Genomics of Populations, 39–65. Oxford University Press, 2022. http://dx.doi.org/10.1093/oso/9780198856566.003.0003.
Full textAbstract:
Genetic variation among individuals within populations and among populations can be assessed at the chromosomal, protein, or DNA sequence level. The best tool or approach depends on the question being asked. Variation in the number or structure of chromosomes can result in reproductive incompatibilities and reduced fitness that influences the success of conservation efforts. Differences in amino acid sequence that alter the electrophoretic mobility of proteins, termed allozymes, were widely used to measure genetic variation and population differentiation on a gene-by-gene basis prior to advances in DNA sequencing. Mitochondria and chloroplasts contain circular DNA molecules that are usually inherited from one parent and are useful for assessing population history and structure. Most studies of genetic variation now rely on the analysis of single nucleotide polymorphisms (SNPs)—variations in nucleotides at a single location within the genome—to understand both selectively neutral and adaptive processes.
Conference papers on the topic "Chloroplast genome studies"
1
Suwastika, I. Nengah, Nurul Aisyah Pakawaru, Rifka, Rahmansyah, Muslimin, Yoko Ishizaki, André Freire Cruz, Zainuddin Basri, and Takashi Shiina. "Diversity of chloroplast genome among local clones of cocoa (Theobroma cacao, L.) from Central Sulawesi." In THE 1ST INTERNATIONAL CONFERENCE ON MATHEMATICS, SCIENCE, AND COMPUTER SCIENCE (ICMSC) 2016: Sustainability and Eco Green Innovation in Tropical Studies for Global Future. Author(s), 2017. http://dx.doi.org/10.1063/1.4975941.
Full text
2
Ulko, D. O., I. I. Gureyeva, R. S. Romanets, and A. A. Kuznetsov. "Molecular-phylogenetic analysis of the Cystopteridaceae family from North Asia based on plastid DNA loci." In Problems of studying the vegetation cover of Siberia. TSU Press, 2020. http://dx.doi.org/10.17223/978-5-94621-927-3-2020-40.
Full textAbstract:
The results of molecular phylogenetic studies based on the sequencing of matK gene and trnG-R intergenic spacer of the chloroplast DNA and analysis of the concatenated data of these loci of North Asian representatives of the Cystopteridaceae family are presented. In the genus Gymnocarpium, a dryopteris-clade was distinguished including species without glandular pubescence of fronds – Gymnocarpium dryopteris. Species having glandular pubescent fronds have formed the robertianum-clade (G. robertianum and G. fedtschenkoanum), and 2 subclades, including G. continentale, G. jessoense, and G. tenuipes. In the genus Cystopteris, the analysis confirmed the separation of C. montana from other Cystopteris species, and the separation of C. sudetica from the C. fragilis-complex. This advocate the recognition of monotypic genus Rhizomatopteris including Rh. montana (≡Cystopteris montana), and allows to recognize the section Khokhrjakovia (with C. sudetica) within the genus Cystopteris. This analysis did not allow to separate the species of the type subgenus Cystopteris (C. fragilis-complex) from each other.
Reports on the topic "Chloroplast genome studies"
1
Azem, Abdussalam, George Lorimer, and Adina Breiman. Molecular and in vivo Functions of the Chloroplast Chaperonins. United States Department of Agriculture, June 2011. http://dx.doi.org/10.32747/2011.7697111.bard.
Full textAbstract:
We present here the final report for our research project entitled "The molecular and in vivo functions of the chloroplast chaperonins”. Over the past few decades, intensive investigation of the bacterial GroELS system has led to a basic understanding of how chaperonins refold denatured proteins. However, the parallel is limited in its relevance to plant chaperonins, since the plant system differs from GroEL in genetic complexity, physiological roles of the chaperonins and precise molecular structure. Due to the importance of plant chaperonins for chloroplast biogenesis and Rubisco assembly, research on this topic will have implications for many vital applicative fields such as crop hardiness and efficiency of plant growth as well as the production of alternative energy sources. In this study, we set out to investigate the structure and function of chloroplast chaperonins from A. thaliana. Most plants harbor multiple genes for chaperonin proteins, making analysis of plant chaperonin systems more complicated than the GroEL-GroES system. We decided to focus on the chaperonins from A. thaliana since the genome of this plant has been well defined and many materials are available which can help facilitate studies using this system. Our proposal put forward a number of goals including cloning, purification, and characterization of the chloroplast cpn60 subunits, antibody preparation, gene expression patterns, in vivo analysis of oligomer composition, preparation and characterization of plant deletion mutants, identification of substrate proteins and biophysical studies. In this report, we describe the progress we have made in understanding the structure and function of chloroplast chaperonins in each of these categories.
2
Stern, David B., and Gadi Schuster. Manipulation of Gene Expression in the Chloroplast: Control of mRNA Stability and Transcription Termination. United States Department of Agriculture, December 1993. http://dx.doi.org/10.32747/1993.7568750.bard.
Full textAbstract:
Chloroplasts are the site of photosynthesis and of other essential biosynthetic activities in plant cells. Chloroplasts are semi-autonomous organelles, since they contain their own genomes and protein biosynthetic machinery, but depend on the coordinate expression of nuclear genes to assemble macromolecular complexes. The bioeingineering of plants requires manipulation of chloroplast gene expression, and thus a knowledge of the molecular mechanisms that modulate mRNA and protein production. In this proposal the heterotrophic green alga Chlamydomonas reinhardtii has been used as a model system to understand the control and interrelationships between transcription termination, mRNA 3' end processing and mRNA stability in chloroplasts. Chlamydomonas is a unique and ideal system in which to address these issues, because the chloroplast can be easily manipulated by genetic transformation techniques. This research uncovered new and important information on chloroplast mRNA 3' end formation and mRNA stability. In particular, the 3' untranslated regions of chloroplast mRNAs were shown not to be efficient transcription terminators. The endonucleolytic site in the 3' untranslated region was characterized by site directed mutagensis and the role of several 3' untranslated regions in modulating RNA stability and translation has been studied. This information will allow us to experimentally manipulate the expression of chloroplast genes in vivo by post-transcriptional mechanisms, and should be widely applicable to other higher plant systems.
3
Stern, David, and Gadi Schuster. Manipulation of Gene Expression in the Chloroplast. United States Department of Agriculture, September 2000. http://dx.doi.org/10.32747/2000.7575289.bard.
Full textAbstract:
The steady-state level of a given mRNA is determined by its rates of transcription and degradation. The stabilities of chloroplast mRNAs vary during plant development, in part regulating gene expression. Furthermore, the fitness of the organelle depends on its ability to destroy non-functional transcripts. In addition, there is a resurgent interest by the biotechnology community in chloroplast transformation due to the public concerns over pollen transmission of introduced traits or foreign proteins. Therefore, studies into basic gene expression mechanisms in the chloroplast will open the door to take advantage of these opportunities. This project was aimed at gaining mechanistic insights into mRNA processing and degradation in the chloroplast and to engineer transcripts of varying stability in Chlamydomonas reinhardtii cells. This research uncovered new and important information on chloroplast mRNA stability, processing, degradation and translation. In particular, the processing of the 3' untranslated regions of chloroplast mRNAs was shown to be important determinants in translation. The endonucleolytic site in the 3' untranslated region was characterized by site directed mutagensis. RNA polyadenylation has been characterized in the chloroplast of Chlamydomonas reinhardtii and chloroplast transformants carrying polyadenylated sequences were constructed and analyzed. Data obtained to date suggest that chloroplasts have gene regulatory mechanisms which are uniquely adapted to their post-endosymbiotic environment, including those that regulate RNA stability. An exciting point has been reached, because molecular genetic studies have defined critical RNA-protein interactions that participate in these processes. However, much remains to be learned about these multiple pathways, how they interact with each other, and how many nuclear genes are consecrated to overseeing them. Chlamydomonas is an ideal model system to extend our understanding of these areas, given its ease of manipulation and the existing knowledge base, some of which we have generated.
4
Schuster, Gadi, and David Stern. Integrated Studies of Chloroplast Ribonucleases. United States Department of Agriculture, September 2011. http://dx.doi.org/10.32747/2011.7697125.bard.
Full textAbstract:
Gene regulation at the RNA level encompasses multiple mechanisms in prokaryotes and eukaryotes, including splicing, editing, endo- and exonucleolytic cleavage, and various phenomena related to small or interfering RNAs. Ribonucleases are key players in nearly all of these post-transcriptional mechanisms, as the catalytic agents. This proposal continued BARD-funded research into ribonuclease activities in the chloroplast, where RNase mutation or deficiency can cause metabolic defects and is often associated with plant chlorosis, embryo or seedling lethality, and/or failure to tolerate nutrient stress. The first objective of this proposal was to examined a series of point mutations in the PNPase enzyme of Arabidopsis both in vivo and in vitro. This goal is related to structure-function analysis of an enzyme whose importance in many cellular processes in prokaryotes and eukaryotes has only begun to be uncovered. PNPase substrates are mostly generated by endonucleolytic cleavages for which the catalytic enzymes remain poorly described. The second objective of the proposal was to examine two candidate enzymes, RNase E and RNase J. RNase E is well-described in bacteria but its function in plants was still unknown. We hypothesized it catalyzes endonucleolytic cleavages in both RNA maturation and decay. RNase J was recently discovered in bacteria but like RNase E, its function in plants had yet to be explored. The results of this work are described in the scientific manuscripts attached to this report. We have completed the first objective of characterizing in detail TILLING mutants of PNPase Arabidopsis plants and in parallel introducing the same amino acids changes in the protein and characterize the properties of the modified proteins in vitro. This study defined the roles for both RNase PH core domains in polyadenylation, RNA 3’-end maturation and intron degradation. The results are described in the collaborative scientific manuscript (Germain et al 2011). The second part of the project aimed at the characterization of the two endoribonucleases, RNase E and RNase J, also in this case, in vivo and in vitro. Our results described the limited role of RNase E as compared to the pronounced one of RNase J in the elimination of antisense transcripts in the chloroplast (Schein et al 2008; Sharwood et al 2011). In addition, we characterized polyadenylation in the chloroplast of the green alga Chlamydomonas reinhardtii, and in Arabidopsis (Zimmer et al 2009). Our long term collaboration enabling in vivo and in vitro analysis, capturing the expertise of the two collaborating laboratories, has resulted in a biologically significant correlation of biochemical and in planta results for conserved and indispensable ribonucleases. These new insights into chloroplast gene regulation will ultimately support plant improvement for agriculture.
5
Schuster, Gadi, and David Stern. Integration of phosphorus and chloroplast mRNA metabolism through regulated ribonucleases. United States Department of Agriculture, August 2008. http://dx.doi.org/10.32747/2008.7695859.bard.
Full textAbstract:
New potential for engineering chloroplasts to express novel traits has stimulated research into relevant techniques and genetic processes, including plastid transformation and gene regulation. This proposal continued our long time BARD-funded collaboration research into mechanisms that influence chloroplast RNA accumulation, and thus gene expression. Previous work on cpRNA catabolism has elucidated a pathway initiated by endonucleolytic cleavage, followed by polyadenylation and exonucleolytic degradation. A major player in this process is the nucleus-encoded exoribonuclease/polymerasepolynucleotidephoshorylase (PNPase). Biochemical characterization of PNPase has revealed a modular structure that controls its RNA synthesis and degradation activities, which in turn are responsive to the phosphate (P) concentration. However, the in vivo roles and regulation of these opposing activities are poorly understood. The objectives of this project were to define how PNPase is controlled by P and nucleotides, using in vitro assays; To make use of both null and site-directed mutations in the PNPgene to study why PNPase appears to be required for photosynthesis; and to analyze plants defective in P sensing for effects on chloroplast gene expression, to address one aspect of how adaptation is integrated throughout the organism. Our new data show that P deprivation reduces cpRNA decay rates in vivo in a PNPasedependent manner, suggesting that PNPase is part of an organismal P limitation response chain that includes the chloroplast. As an essential component of macromolecules, P availability often limits plant growth, and particularly impacts photosynthesis. Although plants have evolved sophisticated scavenging mechanisms these have yet to be exploited, hence P is the most important fertilizer input for crop plants. cpRNA metabolism was found to be regulated by P concentrations through a global sensing pathway in which PNPase is a central player. In addition several additional discoveries were revealed during the course of this research program. The human mitochondria PNPase was explored and a possible role in maintaining mitochondria homeostasis was outlined. As polyadenylation was found to be a common mechanism that is present in almost all organisms, the few examples of organisms that metabolize RNA with no polyadenylation were analyzed and described. Our experiment shaded new insights into how nutrient stress signals affect yield by influencing photosynthesis and other chloroplast processes, suggesting strategies for improving agriculturally-important plants or plants with novel introduced traits. Our studies illuminated the poorly understood linkage of chloroplast gene expression to environmental influences other than light quality and quantity. Finely, our finding significantly advanced the knowledge about polyadenylation of RNA, the evolution of this process and its function in different organisms including bacteria, archaea, chloroplasts, mitochondria and the eukaryotic cell. These new insights into chloroplast gene regulation will ultimately support plant improvement for agriculture
6
Steffens, John, Eithan Harel, and Alfred Mayer. Coding, Expression, Targeting, Import and Processing of Distinct Polyphenoloxidases in Tissues of Higher Plants. United States Department of Agriculture, November 1994. http://dx.doi.org/10.32747/1994.7613008.bard.
Full textAbstract:
Polyphenol oxidase (PPO) catalyzes the oxidation of phenols to quinones at the expense of O2. PPOs are ubiquitous in higer plants, and their role in oxidative browning of plant tissues causes large annual losses to food production. Despite the importance of PPOs to agriculture, the function(s) of PPOs in higher plants are not understood. Among other roles, PPOs have been proposed to participate in aspects of chloroplast metabolism, based on their occurrence in plastids and high Km for O2. Due to the ability of PPO to catalyze formation of highly reactive quinones, PPOs have also been proposed to be involved in a wide array of defensive interactions with insect, bacterial, and fungal pests. Physiological and biochemical studies of PPO have provided few answers to the major problems of PPO function, subcellular localization, and biochemical properties. This proposal achieved the following major objectives: cloning of PPO cDNAs in potato and tomato; characterization of the tomato PPO gene family; antisense downregulation of the tomato PPO gene family; and reduction in post-harvest enzymic browning of potato through expression of antisense PPO genes under the control of tuber-specific promoters. In addition, we established the lumenal localization of PPO, characterized and clarified the means by which PPOs are imported and processed by chloroplasts, and provided insight into the factors which control localization of PPOs. This proposal has thereby provided fundamental advances in the understanding of this enzyme and the control of its expression.
7
Steffens, John C., and Eithan Harel. Polyphenol Oxidases- Expression, Assembly and Function. United States Department of Agriculture, January 1995. http://dx.doi.org/10.32747/1995.7571358.bard.
Full textAbstract:
Polyphenol oxidases (PPOs) participate in the preparation of many plant products on the one hand and cause considerable losses during processing of plant products on the other hand. However, the physiological functions of plant PPO were still a subject of controversy at the onset of the project. Preliminary observations that suggested involvement of PPOs in resistance to herbivores and pathogens held great promise for application in agriculture but required elucidation of PPO's function if modulation of PPO expression is to be considered for improving plant protection or storage and processing of plant products. Suggestions on a possible role of PPO in various aspects of chloroplast metabolism were also relevant in this context. The characterization of plant PPO genes opened a way for achieving these goals. We reasoned that "understanding PPO targeting and routing, designing ways to manipulate its expression and assessing the effects of such modifications will enable determination of the true properties of the enzyme and open the way for controlling its activity". The objective of the project was to "obtain an insight into the function and biological significance of PPOs" by examining possible function(s) of PPO in photosynthesis and plant-pest interactions using transgenic tomato plants; extending our understanding of PPO routing and assembly and the mechanism of its thylakoid translocation; preparing recombinant PPOs for use in import studies, determination of the genuine properties of PPOs and understanding its assembly and determining the effect of PPO's absence on chloroplast performance. Results obtained during work on the project made it necessary to abandon some minor objectives and devote the effort to more promising topics. Such changes are mentioned in the 'Body of the report' which is arranged according to the objectives of the original proposal. The complex expression pattern of tomato PPO gene family was determined. Individual members of the family are differentially expressed in various parts of the plant and subjected to developmentally regulated turnover. Some members are differentially regulated also by pathogens, wounding and chemical wound signals. Wounding systemically induces PPO activity and level in potato. Only tissues that are developmentally competent to express PPO are capable of responding to the systemic wounding signal by increased accumulation of PPO mRNA. Down regulation of PPO genes causes hyper susceptibility to leaf pathogens in tomato while over expression regulation of PPO expression in tomato plants is their apparent increased tolerance to drought. Both the enhanced disease resistance conferred by PPO over expression and the increased stress tolerance due to down regulation can be used in the engineering of improved crop plants. Photosynthesis rate and variable fluorescence measurements in wild type, and PPO-null and over expressing transgenic tomato lines suggest that PPO does not enable plants to cope better with stressful high light intensities or reactive oxygen species. Rather high levels of the enzyme aggravate the damage caused under such conditions. Our work suggests that PPO's primary role is in defending plants against pathogens and herbivores. Jasmonate and ethylene, and apparently also salicylate, signals involved in responses to wounding and defense against herbivores and pathogens, enhance markedly and specifically the competence of chloroplasts to import and process pPPO. The interaction of the precursor with thylakoid membranes is primarily affected. The routing of PPO shows other unusual properties: stromal processing occurs in two sites, resulting in intermediates that are translocated across thylakoids by two different mechanisms - a DpH- and a Sec-dependent one. It is suggested that the dual pattern of processing and routing constitutes a'fail safe' mechanism, reflecting the need for a rapid and flexible response to defense challenges. Many of the observations described above should be taken into consideration when manipulation of PPO expression is contemplated for use in crop improvement.