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Jean David Rochaix - One of the best experts on this subject based on the ideXlab platform.
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mterf8 a member of the mitochondrial transcription termination factor family is involved in the transcription termination of Chloroplast Gene psbj
Plant Physiology, 2020Co-Authors: Haibo Xiong, Jean David Rochaix, Qingbo Yu, Chao Huang, Jing Wang, Jiaxing Zhang, Linshan Ye, Zhongnan YangAbstract:Members of the mitochondrial transcription terminator factor (mTERF) family, originally identified in vertebrate mitochondria, are involved in the termination of organellular transcription. In plants, mTERF proteins are mainly localized in Chloroplasts and mitochondria. In Arabidopsis (Arabidopsis thaliana), mTERF8/pTAC15 was identified in the plastid-encoded RNA polymerase (PEP) complex, the major RNA polymerase of Chloroplasts. In this work, we demonstrate that mTERF8 is associated with the PEP complex. An mTERF8 knockout line displayed a wild-type–like phenotype under standard growth conditions, but showed impaired efficiency of photosystem II electron flow. Transcription of most Chloroplast Genes was not substantially affected in the mterf8 mutant; however, the level of the psbJ transcript from the psbEFLJ polycistron was increased. RNA blot analysis showed that a larger transcript accumulates in mterf8 than in the wild type. Thus, abnormal transcription and/or RNA processing occur for the psbEFLJ polycistron. Circular reverse transcription PCR and sequence analysis showed that the psbJ transcript terminates 95 nucleotides downstream of the translation stop codon in the wild type, whereas its termination is aberrant in mterf8. Both electrophoresis mobility shift assays and Chloroplast chromatin immunoprecipitation analysis showed that mTERF8 specifically binds to the 3′ terminal region of psbJ. Transcription analysis using the in vitro T7 RNA polymerase system showed that mTERF8 terminates psbJ transcription. Together, these results suggest that mTERF8 is specifically involved in the transcription termination of the Chloroplast Gene psbJ.
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Conditional repression of essential Chloroplast Genes: Evidence for new plastid signaling pathways.
Biochimica et biophysica acta, 2014Co-Authors: Jean David Rochaix, Silvia RamundoAbstract:The development of a repressible Chloroplast Gene expression system in Chlamydomonas reinhardtii has opened the door for studying the role of essential Chloroplast Genes. This approach has been used to analyze three Chloroplast Genes of this sort coding for the α subunit of RNA polymerase (rpoA), a ribosomal protein (rps12) and the catalytic subunit of the ATP-dependent ClpP protease (clpP1). Depletion of the three corresponding proteins leads to growth arrest and cell death. Shutdown of Chloroplast transcription and translation increases the abundance of a set of plastid transcripts that includes mainly those involved in transcription, translation and proteolysis and reveals multiple regulatory feedback loops in the Chloroplast Gene circuitry. Depletion of ClpP profoundly affects plastid protein homeostasis and elicits an autophagy-like response with extensive cytoplasmic vacuolization of cells. It also triggers changes in Chloroplast and nuclear Gene expression resulting in increased abundance of chaperones, proteases, ubiquitin-related proteins and proteins involved in lipid trafficking and thylakoid bioGenesis. These features are hallmarks of an unfolded protein response in the Chloroplast and raise new questions on plastid protein homeostasis and plastid signaling. This article is part of a Special Issue entitled: Chloroplast BioGenesis.
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Repression of Essential Chloroplast Genes Reveals New Signaling Pathways and Regulatory Feedback Loops in Chlamydomonas
The Plant cell, 2013Co-Authors: Silvia Ramundo, Michèle Rahire, Olivier Schaad, Jean David RochaixAbstract:Although reverse Genetics has been used to elucidate the function of numerous Chloroplast proteins, the characterization of essential plastid Genes and their role in Chloroplast bioGenesis and cell survival has not yet been achieved. Therefore, we developed a robust repressible Chloroplast Gene expression system in the unicellular alga Chlamydomonas reinhardtii based mainly on a vitamin-repressible riboswitch, and we used this system to study the role of two essential Chloroplast Genes: ribosomal protein S12 (rps12), encoding a plastid ribosomal protein, and rpoA, encoding the α-subunit of Chloroplast bacterial-like RNA polymerase. Repression of either of these two Genes leads to the arrest of cell growth, and it induces a response that involves changes in expression of nuclear Genes implicated in Chloroplast bioGenesis, protein turnover, and stress. This response also leads to the overaccumulation of several plastid transcripts and reveals the existence of multiple negative regulatory feedback loops in the Chloroplast Gene circuitry.
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Potential for hydrogen production with inducible Chloroplast Gene expression in Chlamydomonas
Proceedings of the National Academy of Sciences, 2007Co-Authors: R. Surzycki, Gilles Peltier, Laurent Cournac, Jean David RochaixAbstract:An inducible Chloroplast Gene expression system was developed in Chlamydomonas reinhardtii by taking advantage of the properties of the copper-sensitive cytochrome c(6) promoter and of the nucleus-encoded Nac2 Chloroplast protein. This protein is specifically required for the stable accumulation of the Chloroplast psbD RNA and acts on its 5' UTR. A construct containing the Nac2 coding sequence fused to the cytochrome c(6) promoter was introduced into the nac2-26 mutant strain deficient in Nac2. In this transformant, psbD is expressed in copper-depleted but not in copper-replete medium. Because psbD encodes the D2 reaction center polypeptide of photosystem II (PSII), the repression of psbD leads to the loss of PSII. We have tested this system for hydrogen production. Upon addition of copper to cells pregrown in copper-deficient medium, PSII levels declined to a level at which oxygen consumption by respiration exceeded oxygen evolution by PSII. The resulting anaerobic conditions led to the induction of hydrogenase activity. Because the Cyc6 promoter is also induced under anaerobic conditions, this system opens possibilities for sustained cycling hydrogen production. Moreover, this inducible Gene expression system is applicable to any Chloroplast Gene by replacing its 5' UTR with the psbD 5' UTR in the same Genetic background. To make these strains phototrophic, the 5' UTR of the psbD Gene was replaced by the petA 5' UTR. As an example, we show that the reporter Gene aadA driven by the psbD 5' UTR confers resistance to spectinomycin in the absence of copper and sensitivity in its presence in the culture medium.
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Selectable marker recycling in the Chloroplast
Molecular & general genetics : MGG, 1996Co-Authors: Nicolas Fischer, Otello Stampacchia, Kevin Redding, Jean David RochaixAbstract:The bacterial GeneaadA is an important and widely used selectable marker for manipulation of the Chloroplast genome through biolistic transformation. Because no other such marker is available, two strategies for recycling of theaadA cassette have been developed. One utilizes homologous recombination between two direct repeats flanking theaadA cassette to allow its loss under non-selective growth conditions. A second strategy is to perform co-transformation with a plasmid containing a modified, non-essential Chloroplast Gene and another plasmid in which theaadA cassette disrupts a Chloroplast Gene known to be essential for survival. Under selective growth conditions the first mutation can be transferred to all Chloroplast DNA copies whereas theaadA insertion remains heteroplasmic. Loss of the selectable marker can be achieved subsequently by growing the cells on non-selective media. In both cases it is possible to reuse theaadA cassette for the stepwise disruption or mutaGenesis of any Gene in the same strain.
Lixin Zhang - One of the best experts on this subject based on the ideXlab platform.
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interaction of the pentatricopeptide repeat protein delayed greening 1 with sigma factor sig6 in the regulation of Chloroplast Gene expression in arabidopsis cotyledons
Plant Journal, 2010Co-Authors: Wei Chi, Juan Mao, Meijuan Zou, Lixin ZhangAbstract:The pentatricopeptide-repeat (PPR) protein DELAYED GREENING 1 (DG1) has been shown to be involved in the regulation of early Chloroplast development and Chloroplast Gene expression in Arabidopsis. To gain insight into the mode of DG1 action, we used a yeast two-hybrid screening approach and identified a partner, SIG6, which is a Chloroplast sigma factor responsible for the transcription of plastid-encoded RNA polymerase (PEP)-dependent Chloroplast Genes in cotyledons. Further analysis showed that the C-terminal region of DG1 and the N-terminal region of SIG6 are responsible for such interactions. High-level expression of a truncated C-terminal DG1 in wild-type Arabidopsis caused a dominant-negative phenotype. The sig6 dg1 double mutant displayed a more severe chlorotic phenotype, and the PEP-dependent Chloroplast Gene transcripts were greatly reduced compared with transcript levels in the single mutants. Overexpression of SIG6 rescued the chlorophyll deficiency in dg1 cotyledons but not in young leaves. In addition, increased SIG6 promoted PEP-dependent Chloroplast Gene transcript accumulation in the dg1 mutant background. These results suggest that the interaction of DG1 and SIG6 is functionally significant in the regulation of PEP-dependent Chloroplast Gene transcription in Arabidopsis cotyledons.
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Interaction of the pentatricopeptide‐repeat protein DELAYED GREENING 1 with sigma factor SIG6 in the regulation of Chloroplast Gene expression in Arabidopsis cotyledons
The Plant journal : for cell and molecular biology, 2010Co-Authors: Wei Chi, Juan Mao, Meijuan Zou, Lixin ZhangAbstract:The pentatricopeptide-repeat (PPR) protein DELAYED GREENING 1 (DG1) has been shown to be involved in the regulation of early Chloroplast development and Chloroplast Gene expression in Arabidopsis. To gain insight into the mode of DG1 action, we used a yeast two-hybrid screening approach and identified a partner, SIG6, which is a Chloroplast sigma factor responsible for the transcription of plastid-encoded RNA polymerase (PEP)-dependent Chloroplast Genes in cotyledons. Further analysis showed that the C-terminal region of DG1 and the N-terminal region of SIG6 are responsible for such interactions. High-level expression of a truncated C-terminal DG1 in wild-type Arabidopsis caused a dominant-negative phenotype. The sig6 dg1 double mutant displayed a more severe chlorotic phenotype, and the PEP-dependent Chloroplast Gene transcripts were greatly reduced compared with transcript levels in the single mutants. Overexpression of SIG6 rescued the chlorophyll deficiency in dg1 cotyledons but not in young leaves. In addition, increased SIG6 promoted PEP-dependent Chloroplast Gene transcript accumulation in the dg1 mutant background. These results suggest that the interaction of DG1 and SIG6 is functionally significant in the regulation of PEP-dependent Chloroplast Gene transcription in Arabidopsis cotyledons.
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the pentratricopeptide repeat protein delayed greening1 is involved in the regulation of early Chloroplast development and Chloroplast Gene expression in arabidopsis
Plant Physiology, 2008Co-Authors: Dongyuan Zhang, Congming Lu, Fan Chen, Lixin ZhangAbstract:An Arabidopsis (Arabidopsis thaliana) mutant that exhibited a delayed greening phenotype (dg1) was isolated from a population of activation-tagged Arabidopsis lines. Young, inner leaves of dg1 mutants were initially very pale, but gradually greened and mature outer leaves, more than 3 weeks old, appeared similar to those of wild-type plants. Sequence and transcription analyses showed that DG1 encodes a Chloroplast protein consisting of eight pentratricopeptide repeat domains and that its expression depends on both light and developmental status. In addition, analysis of the transcript profiles of Chloroplast Genes revealed that plastid-encoded polymerase-dependent transcript levels were markedly reduced, while nucleus-encoded polymerase-dependent transcript levels were increased, in dg1 mutants. Thus, DG1 is probably involved in the regulation of plastid-encoded polymerase-dependent Chloroplast Gene expression during early stages of Chloroplast development.
Sujith Puthiyaveetil - One of the best experts on this subject based on the ideXlab platform.
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Sigma factor 1 in Chloroplast Gene transcription and photosynthetic light acclimation.
Journal of experimental botany, 2019Co-Authors: Lauren A. Macadlo, Iskander M. Ibrahim, Sujith PuthiyaveetilAbstract:Sigma factors are dissociable subunits of bacterial RNA polymerase that ensure efficient transcription initiation from Gene promoters. Owing to their prokaryotic origin, Chloroplasts possess a typical bacterial RNA polymerase together with its sigma factor subunit. The higher plant Arabidopsis thaliana contain as many as six sigma factors for the hundred or so of its Chloroplast Genes. The role of this relatively large number of transcription initiation factors for the miniature Chloroplast genome, however, is not fully understood. Using two Arabidopsis T-DNA insertion mutants, we show that sigma factor 1 (SIG1) initiates transcription of a specific subset of Chloroplast Genes. We further show that the photosynthetic control of PSI reaction center Gene transcription requires complementary regulation of the nuclear SIG1 Gene at the transcriptional level. This SIG1 Gene regulation is dependent on both a plastid redox signal and a light signal transduced by the phytochrome photoreceptor.
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Transients in Chloroplast Gene transcription
Biochemical and biophysical research communications, 2008Co-Authors: Sujith Puthiyaveetil, John F. AllenAbstract:Transcriptional regulation of Chloroplast Genes is demonstrated by Quantitative Polymerase Chain Reaction (qPCR). These Genes encode apoproteins of the reaction centres of photosystem I and photosystem II. Their transcription is regulated by changes in wavelength of light selectively absorbed by photosystem I and photosystem II, and therefore by the redox state of an electron carrier located between the two photosystems. Chloroplast transcriptional redox regulation is shown to have greater amplitude, and the kinetics of transcriptional changes are more complex, than suggested by previous experiments using only DNA probes in Northern blot experiments. Redox effects on Chloroplast transcription appear to be superimposed on an endogenous rhythm of mRNA abundance. The functional significance of these transients in Chloroplast Gene transcription is discussed.
Rongcheng Lin - One of the best experts on this subject based on the ideXlab platform.
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A pentatricopeptide repeat protein DUA1 interacts with sigma factor 1 to regulate Chloroplast Gene expression in Rice.
Photosynthesis research, 2020Co-Authors: Mo Weiping, Tang Weijiang, Lijin Tian, Rongcheng LinAbstract:Chloroplast Gene expression is controlled by both plastid-encoded RNA polymerase (PEP) and nuclear-encoded RNA polymerase and is crucial for Chloroplast development and photosynthesis. Environmental factors such as light and temperature can influence transcription in Chloroplasts. In this study, we showed that mutation in DUA1, which encodes a pentatricopeptide repeat (PPR) protein in rice (Oryza sativa), led to deficiency in Chloroplast development and chlorophyll biosynthesis, impaired photosystems, and reduced expression of PEP-dependent transcripts at low temperature especially under low-light conditions. Furthermore, we demonstrated that sigma factor OsSIG1 interacted with DUA1 in vitro and in vivo. Moreover, the levels of chlorophyll and PEP-dependent Gene expression were significantly decreased in the Ossig1 mutants at low-temperature and low-light conditions. Our study reveals that the PPR protein DUA1 plays an important role in regulating PEP-mediated Chloroplast Gene expression through interacting with OsSIG1, thus modulates Chloroplast development in response to environmental signals.
Lauren A. Macadlo - One of the best experts on this subject based on the ideXlab platform.
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Sigma factor 1 in Chloroplast Gene transcription and photosynthetic light acclimation.
Journal of experimental botany, 2019Co-Authors: Lauren A. Macadlo, Iskander M. Ibrahim, Sujith PuthiyaveetilAbstract:Sigma factors are dissociable subunits of bacterial RNA polymerase that ensure efficient transcription initiation from Gene promoters. Owing to their prokaryotic origin, Chloroplasts possess a typical bacterial RNA polymerase together with its sigma factor subunit. The higher plant Arabidopsis thaliana contain as many as six sigma factors for the hundred or so of its Chloroplast Genes. The role of this relatively large number of transcription initiation factors for the miniature Chloroplast genome, however, is not fully understood. Using two Arabidopsis T-DNA insertion mutants, we show that sigma factor 1 (SIG1) initiates transcription of a specific subset of Chloroplast Genes. We further show that the photosynthetic control of PSI reaction center Gene transcription requires complementary regulation of the nuclear SIG1 Gene at the transcriptional level. This SIG1 Gene regulation is dependent on both a plastid redox signal and a light signal transduced by the phytochrome photoreceptor.