Plastids reside in all plant cells, and take on different forms in relation to their cellular function, biochemistry and storage capacity. The modern era of molecular biology and molecular genetics has enabled much to be learnt about how plastids function, and how they relate to their evolutionary past. In this accessible text, Kevin Pyke expertly describes how the plastids are highly complex organelles at the very core of plant cellular function, providing final year undergraduate and graduate students with an overview of plastid biology and recent developments in the field. Topics covered include: a consideration of different plastid types and how they relate to cell function; plastid genomes and how proteins are imported into plastids; photosynthesis and core aspects of plastid biochemistry; plastid signalling and functionality within a cellular context; and plastid genetic manipulation. Supplementary colour images are available online at www.cambridge.org/9780521885010.. • Highly ...
This volume provides a comprehensive look at the biology of plastids, the multifunctional biosynthetic factories that are unique to plants and algae. Fifty-six international experts have contributed 28 chapters that cover all aspects of this large and diverse family of plant and algal organelles. The book is divided into five sections: (I): Plastid Origin and Development; (II): The Plastid Genome and Its Interaction with the Nuclear Genome; (III): Photosynthetic Metabolism in Plastids; (IV): Non-Photosynthetic Metabolism in Plastids; (V): Plastid Differentiation and Response to Environmental Factors. Each chapter includes an integrated view of plant biology from the standpoint of the plastid. The book is intended for a wide audience, but is specifically designed for advanced undergraduate and graduate students and scientists in the fields of photosynthesis, biochemistry, molecular biology, physiology, and plant biology.
Photosynthetic development in any plant requires the intracellular co-ordination of chloroplast and nuclear gene expression programs. In this report, we investigate the role of a nuclear gene in photosynthetic development by examining C4 photosynthetic differentiation in a yellow mutant of maize (Zea mays L.). The plastids undifferentiated (pun) mutation disrupts plastid biogenesis in both bundle sheath and mesophyll cells, at an early developmental stage and in a light-independent manner. Chloroplast thylakoids are disrupted in the mutant and both membrane-associated and soluble chloroplast-encoded proteins accumulate at much reduced levels. The observed plastid morphology is consistent with a general defect in chloroplast biogenesis that is most likely exerted at the post-translational level. Despite aberrant chloroplast development, nuclear photosynthetic genes are expressed normally in pun mutants. Thus, neither functional chloroplasts nor the Pun gene product are required to establish nuclear
We showed in the past that starch accumulation in potato tubers is strongly affected by altering the plastidic ATP/ADP-transporter activity (Tjaden et al., 1998a) leading to a high metabolic-flux control coefficient (Geigenberger et al., 2001). Therefore, we analyzed whether reduced plastidic ATP import capacity governs the end-product accumulation in Arabidopsis embryos to a similar extent as observed in potato. This analysis was further encouraged, since experiments on isolated rapeseed seed-embryo plastids showed that the highest rates of fatty-acid synthesis depend upon the supply with exogenous ATP (Eastmond and Rawsthorne, 1998; Rawsthorne, 2002), whereas a recently developed mathematical carbon-flux model indicated that net ATP import is not required for maximal fatty-acid synthesis in rapeseed embryos (Schwender et al., 2004).. As given in Figure 11, AtNTT1∷T-DNA did not show altered seed weight, lipid, and protein content when compared to wild-type seeds, whereas AtNTT2∷T-DNA seeds ...
Uncorrected OCR) Abstract of thesis entitled PRODUCTION OF TRANSGENIC PLANT-DERIVED VACCINES VIA PLASTID TRANSFORMATION TECHNOLOGY Submitted by Lee Yuk Ting for the degree of Master of Philosophy at The University of Hong Kong in July 2004 With the advent of genetic engineering in higher plants, the need for very large quantities of therapeutic protein at low cost, and the desire to have heat-stable edible vaccines directed at human and animal diseases, transgenic plant-derived vaccines offer a new strategy for the development of safe, inexpensive vaccines against infectious diseases. The first success of plastid transformation in tobacco in 1990 has opened up the opportunities for genetically modifying plastids in higher plants for high level expression of biopharmaceuticals, such as antibodies and vaccines for oral administration. Since each plant cell contains up to 10,000 copies of identical plastid genome, plastid engineering should result in very high levels of transgene expression. In ...
In recent years there has been extensive experimental evidence indicating that the nuclear expression of certain genes , in particular those that encode chloroplast proteins is subject to regulation by signals of retrograde plastid origin . This can be done both at the level of transcription and translation of mRNA . Certain plastid origin signals could be identified - these include metabolic precursor of chlorophyll plastochinonu redox state , thioredoxin and glutathione and phosphoenolpyruvate translocator located in the chloroplast inner envelope membrane . Identity plastid other signals , e.g., regulating cell differentiation and morphogenesis leaf remains unexplained . Signaling plastids - nucleus signaling and dependent on the light remain in a fairly complicated relationships , in some cases, are used for different transduction pathways , in others some of the same . Retrograde signaling is likely to be an important part of global regulatory networks that control metabolism and growth of ...
The plastid (Greek: πλαστός; plastós: formed, molded - plural plastids) is a major double-membrane organelle found in the cells of plants, algae, and some other eukaryotic organisms. Plastids were discovered and named by Ernst Haeckel, but A. F. W. Schimper was the first to grant them a clear definition. Plastids are the site of manufacture and storage of important chemical compounds used by the cell. They often contain pigments used in photosynthesis, and the types of pigments in a plastid determine the cells color. They have a common evolutionary origin and possess a double-stranded DNA molecule that is circular, like that of prokaryotic cells. Those plastids that contain chlorophyll can carry out photosynthesis. Plastids can also store products like starch and can synthesize fatty acids and terpenes, which can be used for producing energy and as raw material for the synthesis of other molecules. For example, the components of the plant cuticle and its epicuticular wax are synthesized ...
The plastid signal was originally defined as a pathway that informs the nucleus of the chloroplast status and results in the modulation of expression of nuclear-encoded plastid protein genes. However, the transfer of chloroplast genes into the nuclear genome is a prerequisite in this scheme, although it should not have been established during the very early phase of chloroplast evolution. We recently demonstrated in a primitive red alga that the plastid-derived Mg-protoporphyrin IX (Mg-ProtoIX) activates nuclear DNA replication through the stabilization of a G1 cyclin, which coordinates the timing of organelle and nuclear DNA replication. This mechanism apparently does not involve any transcriptional regulation in the nucleus, and could have been established prior to gene transfer events. However, a retrograde signal mediating light-responsive gene expression may have been established alongside gene transfer, because essential light sensing and regulatory systems were originally incorporated into plant
The occurrence of RNA in plastids from etiolated and green maize leaves was demonstrated cytochemically, with both the light and the electron microscope. Etiolated leaves were allowed to incorporate tritiated cytidine for several hours and were subsequently fixed in formalin. Radioautographs of leaf sections 2 µ thick showed silver grains over the regions of the cytoplasm containing plastids. Plastids in these sections appeared intensely basophilic when stained with azure B. Both the basophilia and radioactivity were removable with ribonuclease, clearly demonstrating the occurrence of RNA in these organelles. Examination under the electron microscope of similar plastids which had been fixed in formalin revealed a particulate component in the plastid measuring approximately 170 A in diameter. This particulate component was completely removable with ribonuclease. Thus,it was concluded that RNA occurs in a particulate form in plastids from etiolated leaves. Mature plastids, when stained with azure ...
Evaluation of a marker gene operon for plastid transformation and cloning of genes encoding cell wall degrading enzymes in plastid transformation vectors ...
A novel algorithm and original software were used to cluster all proteins encoded in plastids of 72 species of the rhodophytic branch. The results are publicly available at http://lab6.iitp.ru/ppc/redline72/ in a database that allows fast identification of clusters (protein families) both by a fragment of an amino acid sequence and by a phylogenetic profile of a protein. No such integral clustering with the corresponding functions can be found in the public domain. The putative regulons of the transcription factors Ycf28 and Ycf29 encoded in the plastids were identified using the clustering and the database. A regulation of translation initiation was proposed for the ycf24 gene in plastids of certain red algae and apicomplexans as well as a regulation of a putative gene in apicoplasts of Babesia spp. and Theileria parva. The conserved regulation of the ycf24 gene expression and specificity alternation of the transcription factor Ycf28 were shown in the plastids. A phylogenetic tree of plastids was
What is a plastid Cell | Process of Photosynthesis | Chloroplasts, chromoplast, leucoplasts & Other Plastids. Learn more about [email protected]
During the evolution of the eukaryotic cell, plastids and mitochondria arose from an endosymbiotic process, which determined the presence of three genetic compartments into the incipient plant cell. After that, these three genetic materials from host and symbiont suffered several rearrangements, bringing on a complex interaction between nuclear and organellar gene products. Nowadays, plastids harbor a small genome with ~130 genes in a 100-220 kb sequence in higher plants. Plastid genes are mostly highly conserved between plant species, being useful for phylogenetic analysis in higher taxa. However, intergenic spacers have a relatively higher mutation rate and are important markers to study genetic diversity and divergence within natural plant populations. The predominant uniparental inheritance of plastids is like a highly desirable feature for phylogeny studies. Moreover, the gene content and genome rearrangements are efficient tools to capture and understand evolutionary events between different plant
Ferredoxin-NADP+-oxidoreductase (FNR) is a FAD-containg enzyme found both in the chloroplasts and non-photosynthetic plastids of higher plants. In chloroplasts, FNR has a well-defined role in linear electron flow, and in the root plastids, FNR is needed for nitrogen metabolism. In Arabidopsis thaliana, FNR is encoded by a gene family: At1g30510 and At4g05390 encode the root isozyme of FNR and At5g66190 and At1g20020 encode the leaf/chloroplast isozyme, which share a high degree of homology. Since FNR is a crucial determinant for the acclimation of the photosynthetic machinery, we have recently focused on resolving the specific physiological roles of the two distinct chloroplast-targeted FNR isoforms using the Arabidopsis fnr knock-out mutants (Lintala et al. 2007; 2009; 2012). We have also resolved the binding partner and the physiological significance of FNR shuttling within the chloroplast (Benz et al. 2009; 2010; Lintala et al.2014), and established differential drought stress -induced ...
Plastid stromules are stroma-filled tubules that extend from the surface of plastids in higher plants and allow the exchange of protein molecules between plastids. These structures are highly dynamic; stromules change both their shape and position in the cytoplasm very rapidly. Previous studies with microfilament inhibitors indicated that stromule shape and movement are dependent on the actin cytoskeleton. To learn more about the nature of the interactions of stromules and the cytoskeleton, we imaged fluorescently-labeled microfilaments and plastids. We have used Arabidopsis thaliana plants expressing green fluorescent protein fused to the human actin-binding protein talin to observe microfilaments and their relationship to stromules in vivo. Microfilaments were observed in close contact with stromules and plastid bodies of hypocotyl epidermis. Time-lapse confocal microscopy revealed that microfilament rearrangements were associated with changes in plastid and stromule morphology and position. We also
Plastids are in plants. The most common form are chloroplasts, which are green, but there are many types of plastids, most of them can pass from one form to another. They originated in procaryotic cells so they have DNA and ribosoms. The plastidial DNA contains many genes that the plant can not do without, like the gene for turning glucose into ...
Protein ARC5; Probable GTPase component of both plastid and peroxisme division machinery. Required for the last steps of plastid division specifically in mesophyll-cell, when the narrow isthmus breaks, facilitating the separation of the daughter plastids. Necessary for peroxisome activities. Seems to influence stromule (stroma-filled tubular extensions of the plastid envelope membrane) length and frequency (777 aa ...
A global phylogeny of major eukaryotic lineages is a significant and ongoing challenge to molecular phylogenetics. Currently, there are five hypothesized major lineages or supergroups' of eukaryotes. One of these, the chromalveolates, represents a large fraction of protist and algal diversity. The chromalveolate hypothesis was originally based on similarities between the photosynthetic organelles (plastids) found in many of its members and has been supported by analyses of plastid-related genes. However, since plastids can move between eukaryotic lineages, it is important to provide additional support from data generated from the nuclear-cytosolic host lineage. Genes coding for six different cytosolic proteins from a variety of chromalveolates (yielding 68 new gene sequences) have been characterized so that multiple gene analyses, including all six major lineages of chromalveolates, could be compared and concatenated with data representing all five hypothesized supergroups. Overall support for
Plastid-to-nucleus retrograde signaling coordinates nuclear gene expression with chloroplast function and is essential for the photoautotrophic life-style of plants. Three retrograde signals have been described, but little is known of their signaling pathways. We show here that GUN1, a chloroplast-localized pentatricopeptide-repeat protein, and ABI4, an Apetala 2 (AP2)-type transcription factor, are common to all three pathways. ABI4 binds the promoter of a retrograde-regulated gene through a conserved motif found in close proximity to a light-regulatory element. We propose a model in which multiple indicators of aberrant plastid function in Arabidopsis are integrated upstream of GUN1 within plastids, which leads to ABI4-mediated repression of nuclear-encoded genes. |P /|
Plastid transformation technology has been well established and widely utilized in plant transgenic research. In comparison with conventional nuclear gene transformation techniques, plastid engineering offers several potential advantages such as (i) more than 10-100 times greater expression levels than the conventional nuclear transformation system, (ii) a more convenient methodology for transferring multiple genes into plants via gene stacking methods, (iii) elimination of position effects in chloroplasts, which thereby reduces the chances for transgene silencing, (iv) minimal chance for transgene flow by pollen contamination due to maternal inheritance (Verma and Daniell, 2007).. One of the key aspects for the plastid transformation system is to employ a plastidic sequence to exchange exogenous genes into the chloroplast genome via homologous recombination. The usage of genetic markers, which enable the selective enrichment of ptDNA copies, is also a critical component for plastid ...
In plants, the photosynthetic light reactions provide the energy for major plastid localized pathways, such as CO2 assimilation, the synthesis of starch, fatty acids, several amino acids, nucleic acids, and the reductive assimilation of inorganic ions like nitrate and sulfate (Weber et al., 2005; Zrenner et al., 2006). To supply the cell and the organism with these primary metabolites, a large number of precursors, end products, and intermediates have to be transported across the organelle envelope membrane and therefore present-day plastids are extensively connected to the cytoplasm by metabolite transporters that reside in the envelope membranes (Tegeder and Weber, 2006; Weber and Fischer, 2007).. Chloroplasts originated approximately 1.6 billion years ago through a single primary endosymbiosis between a nonphotosynthetic primitive mitochondriate eukaryote and a cyanobacterium (Yoon et al., 2004; Bhattacharya et al., 2007; Reyes-Prieto et al., 2007). Within a period of 0.15 billion years, ...
Plastids in plants and algae evolved from the endosymbiotic integration of a cyanobacterium by a heterotrophic eukaryote. New plastids can only emerge through fission; thus, the synchronization of bacterial division with the cell cycle of the eukaryotic host was vital to the origin of phototrophic eukaryotes. Most of the sampled algae house a single plastid per cell and basal-branching relatives of polyplastidic lineages are all monoplastidic, as are some non-vascular plants during certain stages of their life cycle. In this Review, we discuss recent advances in our understanding of the molecular components necessary for plastid division, including those of the peptidoglycan wall (of which remnants were recently identified in moss), in a wide range of phototrophic eukaryotes. Our comparison of the phenotype of 131 species harbouring plastids of either primary or secondary origin uncovers that one prerequisite for an algae or plant to house multiple plastids per nucleus appears to be the loss of ...
Recent findings are summarized in support of the view that mitochondria (including hydrogenosomes) and plastids (including complex ones) descend from symbiotic associations of once free-living organisms. The reasoning behind endosymbiotic hypotheses stems from a comparison of biochemistry and physiology in organelles with that in free-living cells; their strength is shown to lie in the specific testable predictions they generate about expected similarity patterns among genes. Although disdained for many decades, endosymbiotic hypotheses have gradually become very popular. In the wake of that popularity, endosymbiotic hypotheses have been formulated to explain the origins of eukaryotic cell compartments and structures that have no biochemical similarity to free-living cells. In particular, it has become fashionable in recent years to entertain the century-old notion that the nucleus might also descend from an endosymbiotic bacterium. A critique of that hypothesis is formulated and a simple ...
Single-strand annealing mechanism for plastid DNA replication. This single-strand annealing (SSA), recombination-dependent replication model for ptDNA is based
Phosphoenolpyruvate (PEP) plays an essential role in plant metabolism. In catabolic direction, it delivers ATP and pyruvate by the action of pyruvate kinase, which can be fed into mitochondrial respiration. PEP and pyruvate also represent essential precursors for anabolism i.e. PEP is the precursor for the synthesis of aromatic amino acids, secondary plant products and pyruvate is important for the production of fatty acids, branched-chain amino acids or isoprenoids via the mevalonate-independent way. These pathways are exclusively localized to the plastid stroma. PEP may be imported into the plastids via a PEP/phosphate translocator (PPT) of the inner envelope membrane or it may also be generated inside the stroma by complete plastid glycolysis starting from hexose phosphates. Glycolysis as the main route for PEP production involves the enzymatic sequence of 3-phosphoglycerate to PEP conversion catalyzed by phosphoglyceromutase (PGyM) and enolase (ENO). However, biochemical studies indicate ...
Palmitic acid (16:0) is the most common fatty acid (saturated) found in animals, plants and microorganisms. Coenzyme A (CoA) also presents in living organisms, is bound to Palmitic acid for synthesis and oxidates several fatty acids. These 2 elements reacts to form the first metabolite of our pathway 16:CoA, which is generated by the endoplastic reticulum (plastid membrane). AraGEM model is compounded by 1737 metabolites and 1601 reactions. These elements are organized in the stoichiometric matrix S[1737x1601] to use them in the FBA optimization take into account some constraints. Our efforts were aimed at the optimization of Palmitic Acid or Hexadecanoic32 Acid_acc (16:0), which is the precursor of our pathway. 16:0 is located in the cytosol and the reaction takes place using one influx V1 and two effluxes V2, V3. The efflux V2 was incorporated as an exchange reaction in order to generate branch in the original pathway of 16:0 metabolism. As our metabolic pathway is linear starting from 16:0, ...
The genomics and evolution of carbon fixation. We use the evolution of carbon fixation as a model for studying the origin and evolution and processes and pathways. Our work includes genomic studies of the reverse TCA cycle (e.g., [http://www.pnas.org/cgi/content/full/104/28/11784 here], [http://www.pnas.org/cgi/content/full/99/14/9509 here] and [http://www.ncbi.nlm.nih.gov/pubmed/9595663?ordinalpos=4&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum here]), methylotrophy ([http://biology.plosjournals.org/perlserv/?request=get-document&doi=10.1371/journal.pbio.0020303 here]), Carboxydotrophs (e.g., [http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.0010065 here]), plastid evolution and/or the Calvin cycle (e.g., [http://www.pnas.org/cgi/content/full/102/20/7315 here], [http://www.nature.com/nature/journal/v419/n6906/abs/nature01097.html here], [http://www.nature.com/nature/journal/v415/n6872/abs/415630a.html here], ...
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Plastids have a tremendous importance in plants as they are the photosynthetic organelles. But their importance extends way beyond this physiological role, as they are also part of the regulatory network that controls the life cycle of the entire plant. Our research is focussed on the integration of the cell organelles (plastids as well as mitochondria) into cellular response regulation of plants with a particular focus on dually targeted proteins.
We analysed the size, relative age and chromosomal localization of nuclear sequences of plastid and mitochondrial origin (NUPTs-nuclear plastid DNA and NUMTs-nuclear mitochondrial DNA) in six completely sequenced plant species. We found that the largest insertions showed lower divergence from organelle DNA than shorter insertions in all species, indicating their recent origin. The largest NUPT and NUMT insertions were localized in the vicinity of the centromeres in the small genomes of Arabidopsis and rice. They were also present in other chromosomal regions in the large genomes of soybean and maize. Localization of NUPTs and NUMTs correlated positively with distribution of transposable elements (TEs) in Arabidopsis and sorghum, negatively in grapevine and soybean, and did not correlate in rice or maize. We propose a model where new plastid and mitochondrial DNA sequences are inserted close to centromeres and are later fragmented by TE insertions and reshuffled away from the centromere or ...
plastid: Any of several pigmented cytoplasmic organelles found in plant cells and other organisms, having various physiological functions, such as the synthesis and storage of food.
Jim Cummins wrote: , , In article ,53t6kq$h9j at bignews.shef.ac.uk,, T.S.Bibby at shef.ac.uk (T S , Bibby) wrote: , , , Hello, am doing a project entitled Chloroplasts and Gastarbeiter in , , eukaryotic cells. What is foregin about them and to what extent have , , they become integrated. Anything (references etc) envolving this , , subject would be useful. , , Check out Margulis and Sagan 1986 Origins of Sex Yale University Press Actually, there has been lots of molecular work done on this since the Margulis book. Look to the primary literature for authors such as: Mike Gray, Mike Reith, Richard Hallick. There are tons other references you can find by looking in the references of papers by these authors. Gray wrote a huge review paper in 1992 (Int. Rev. Cytol.) on mitochondria and chloroplasts. When you talk about integrated, I imagine you are thinking of things like transfer of plastid genes of the nucleus. Much plastid DNA has been transferred to the nucleus (one could safely say that ...
Sánchez-Ken, J. G. & L. G. Clark 2010. Phylogeny and a new tribal classification of the Panicoideae sl (Poaceae) based on plastid and nuclear sequence data and structural data. Amer. J. Bot. 97:1732-1748 ...
Klaus SMJ, Kunji ERS, Bozzo GG, Noiriel A, de la Garza RDíaz, Basset GJC, Ravanel S, Rébeillé F, Gregory JF & Hanson AD (2005) Higher plant plastids and cyanobacteria have folate carriers related to those of trypanosomatids. J Biol Chem 280, 38457-63 ...
Advances in single-cell technologies have revealed vast differences between cells once thought to be in the same category, calling into question how we define cell type in the first place ...
Daily News How Gaining and Losing Weight Affects the Body Millions of measurements from 23 people who consumed extra calories every day for a month reveal changes in proteins, metabolites, and gut microbiota that accompany shifts in body mass.. ...
Savolainen, V., M. W. Chase, S. B. Hoot, C. M. Morton, D. E. Soltis, C. Bayer, M. F. Fay, A. Y. d. Bruijn, S. Sullivan, and Y.-L. Qiu. 2000. Phylogenetics of flowering plants based on combined analysis of plastid atpB and rbcL gene sequences. Syst. Biol. 49:306-362 ...
Hereditay acids present in the nucleus are called nucleic acids. They are called so because they were discovered first in the nucleus. But they are present outside the nucleus also that is cytoplasm, mitochondria and plastids. DNA and RNA are the two basic nucleic acids in the living world ...
A cDNA encoding the plastid ω-3 fatty acid desaturase was isolated from a tobacco (Nicotiana tabacum cv. SR1) leaf cDNA library. The amino terminal extension of the deduced amino acid sequence of this clone had a characteristic feature of the transit peptides of plastid-destined proteins. Northern analysis indicated that the mRNA corresponding to this cDNA was present in leaves, but was not detected in roots. Responses to wounding of the plastid and microsome ω-3 desaturase genes were investigated in tobacco leaves. The mRNA level of the plastid ω-3 desaturase gene increased to about 2-fold that of unwounded controls at 12 h after a wounding treatment. On the other hand, the mRNA level of the microsome ω-3 desaturase gene remained constant in the wounded leaves. Linolenic acid contents of major leaf polar lipids increased by wounding. These results indicate that wounding enhances the accumulation of the plastid ω-3 desaturase mRNA, and increases the conversion of linoleic acid to linolenic ...
Most apicomplexan parasites harbor a relict chloroplast, the apicoplast, that is critical for their survival. While the apicoplast maintains a small genome, the bulk of its proteins are nuclear-encoded and imported into the organelle. Several models have been proposed to explain how proteins might cross the four membranes that surround the apicoplast, however experimental data discriminating these models is largely missing. Here we present genetic evidence that apicoplast protein import depends on elements derived from the ER associated protein degradation (ERAD) system of the endosymbiont. We identify two sets of ERAD components in Toxoplasma gondii, one associated with the ER and cytoplasm and one localized to the membranes of the apicoplast. We engineer a conditional null mutant in apicoplast Der1, the putative pore of the apicoplast ERAD complex, and find that loss of Der1Ap results in loss of apicoplast protein import and subsequent death of the parasite ...
The new study at UFs Florida Museum of Natural History analyzed 86 complete plastid genome sequences from a wide range of plant species. Plastids are the plant cell component responsible for photosynthesis.. Previous genetic analyses of Pentapetalae failed to untangle the relationships among living species, suggesting that the plants diverged rapidly over 5 million years. Researchers selected genomes to sequence based on their best guess of genetic relationships from the previous sequencing work.. Genome sequencing is more time-consuming for plants than animals because plastid DNA is about 10 times larger than the mitochondrial DNA used in studying animal genomes. But continual improvements in DNA sequencing technology are now allowing researchers to analyze those larger amounts of data more quickly.. The study provides an important framework for further investigating evolutionary relationships by providing a much clearer picture of the deep divergence that led to the split within flowering ...
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Plants possess acclimation responses in which structural reconfigurations adapt the photosynthetic apparatus to fluctuating illumination. Long-term acclimation involves changes in plastid and nuclear gene expression and is controlled by redox signals from photosynthesis. The kinetics of these signals and the adjustments of energetic and metabolic demands to the changes in the photosynthetic apparatus are currently poorly understood. Using a redox signaling system that preferentially excites either photosystem I or II, we measured the time-dependent impact of redox signals on the transcriptome and metabolome of Arabidopsis thaliana. We observed rapid and dynamic changes in nuclear transcript accumulation resulting in differential and specific expression patterns for genes associated with photosynthesis and metabolism. Metabolite pools also exhibited dynamic changes and indicate readjustments between distinct metabolic states depending on the respective illumination. These states reflect ...
Investigation of the chlorophyll synthesis in plastid membranes:. The initial enzyme to start the synthesis of chlorophyll in light is NADPH-protochlorophyllide oxidoreductase (EC 1.3.1.33, POR). The group has studied the aggregation state of the POR, its localization in the lipid phase of the membranes and the enzyme conformational changes after irradiation, by energy transfer from tryptophan residues of membrane proteins to the fluorescence probes 1-aniline-8-naphthalene sulfonate (ANS) and pyrene. The membranes investigated were those accumulated in dark-grown wheat leaves - prolamellar bodies (PLBs) and prothylakoids (PTs). Changes in protein - probe interactions of the PLBs after irradiation has shown that POR is localized close to the membrane surface, most probably on the level of lipid polar heads. This supports the idea that the enzyme is not an integral membrane protein and is most probably localized on the membrane surface.. Photodynamic effect of pigment precursor in plants:. Some ...
The term evolutionary tinkering refers to evolutionary innovation by recombination of functional units, and includes the creation of novel proteins from pre-existing modules. A novel instance of evolutionary tinkering was recently discovered in the flowering plant genus Nicotiana: the conversion of a nuclear transcription factor into the plastid-resident protein WIN4 (wound-induced clone 4) involved in environmental stress responses. In this issue of the Biochemical Journal, Kodama and Sano now show that two steps are necessary for the establishment of the novel plastid protein: the acquisition of an internal translation initiation site and the use of multiple transcription starts to produce short mRNA variants that encode the plastid-targeted protein form. ...
Chloroplasts contain 3000-4000 different proteins but only a small subset of them is encoded in the plastid genome while the majority is encoded in the nucleus. Expression of these genes therefore requires a high degree of co-ordination between nucleus and chloroplast. This is achieved by a bilateral information exchange between both compartments including nucleus-to-plastid (anterograde) and plastid-to-nucleus (retrograde) signals. The latter represent a functional feedback control which couples the expression of nuclear encoded plastid proteins to the actual functional state of the organelle. The efficiency of photosynthesis is a very important parameter in this context since it is influenced by many environmental conditions and therefore represents a sensor for the residing environment. Components of the photosynthetic electron transport chain exhibit significant changes in their reduction/oxidation (redox) state depending on the photosynthetic electron flow and therefore serve as signalling ...
Chloroplasts contain 3000-4000 different proteins but only a small subset of them is encoded in the plastid genome while the majority is encoded in the nucleus. Expression of these genes therefore requires a high degree of co-ordination between nucleus and chloroplast. This is achieved by a bilateral information exchange between both compartments including nucleus-to-plastid (anterograde) and plastid-to-nucleus (retrograde) signals. The latter represent a functional feedback control which couples the expression of nuclear encoded plastid proteins to the actual functional state of the organelle. The efficiency of photosynthesis is a very important parameter in this context since it is influenced by many environmental conditions and therefore represents a sensor for the residing environment. Components of the photosynthetic electron transport chain exhibit significant changes in their reduction/oxidation (redox) state depending on the photosynthetic electron flow and therefore serve as signalling ...
The results we have shown here and in a previous report (Sauret-Güeto et al., 2006) confirm a strong and specific influence of plastid cues in the regulation of the MEP pathway for isoprenoid biosynthesis. Evidence provided in this work unveils a mechanism for such regulation involving the participation of the plastidic Clp protease complex. Impaired expression of the plastid genome in rif1, rif10, and CAP-treated Col seedlings unexpectedly resulted in increased levels of the plastome-encoded ClpP1 subunit of the catalytic ClpPR core of the complex (Figure 7). It is possible that ClpP1 levels are modulated not only by their biosynthetic rate but also by a regulatory feedback mechanism at the posttranslational level. As a result, a defective production of ClpP1 in the first stages of plastid development might result in an altered proportion of subunits within the ClpPR core and an insufficient Clp protease activity, which in turn might lead to the observed upregulation of ClpP1 levels as a ...
Most heterokonts are biflagellated at some stage of their life cycles, usually at least as gametes. The two flagella are structurally distinct, the leading-end flagella ("tinsel") being branched, the lateral or subapical flagellum is smooth and shorter or even rudimentary. Their plastid envelops consist of 4 membrane layers. The innermost 2 layers are derived from the original cyanobacterial endosymbiont. The next layer is the relic of the cell membrane of the red alga from which the stramenopilie acquired the plastid by seconadry endosymbiosis. The outermost layer is actually the host endoplasmic reticulum, inside of which the plastids reside.. Diatoms are the most familiar members of this group, and are perhaps the most abundant and diverse as well. By some estimates, they may be responsible for up to half of marine primary production. Most are unicellular. Gametes are flagellated, but diploids are non-motile or motile by gliding, and are encased in a intricate 2-part silica (glass) shells. ...
Pathways of intracellular communication: tetrapyrroles and plastid-to-nucleus signaling. Checkpoint signaling: epigenetic events sound the DNA strand-breaks alarm to the ATM proein kinase