Chlamydomonas reinhardtii
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ABSTRACT:
PROVIDER: PRJNA150239 | ENA |
REPOSITORIES: ENA
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Project description:The l-galactose (Smirnoff-Wheeler) pathway represents the major route to l-ascorbic acid (vitamin C) biosynthesis in plants. Arabidopsis thaliana VTC2 and its paralogue VTC5 function as GDP-l-galactose phosphorylases converting GDP-l-galactose to l-galactose-1-P, thus catalyzing the first committed step in the biosynthesis of l-ascorbate. Here we report that the l-galactose pathway of ascorbate biosynthesis described in higher plants is conserved in green algae. The Chlamydomonas reinhardtii genome encodes all the enzymes required for vitamin C biosynthesis via the Smirnoff-Wheeler pathway. We have characterized recombinant C. reinhardtii VTC2 as an active GDP-l-galactose phosphorylase. C. reinhardtii cells exposed to oxidative stress show increased VTC2 mRNA and l-ascorbate levels. We have also shown that enzymatic components of the ascorbate-glutathione system (e.g. ascorbate peroxidase, Mn superoxide dismutase, dehydroascorbate reductase) are up-regulated in response to increased oxidative stress. These results indicate that C. reinhardtii VTC2, like its plant homologs, is a key enzyme in ascorbate biosynthesis in green algae and together with components of the ascorbate recycling system represents the major route in providing protective levels of ascorbate in oxidatively stressed algal cells. Our results suggest that C. reinhardtii cells exposed to oxidative stress conditions produce more ascorbate both by de novo synthesis (Smirnoff-Wheeler pathway) and by recycling via the ascorbate-glutathione cycle. Sampling of Chlamydomonas 2137 exposed to hydrogen peroxide
2012-05-02 | E-GEOD-34826 | biostudies-arrayexpress
Project description:The l-galactose (Smirnoff-Wheeler) pathway represents the major route to l-ascorbic acid (vitamin C) biosynthesis in plants. Arabidopsis thaliana VTC2 and its paralogue VTC5 function as GDP-l-galactose phosphorylases converting GDP-l-galactose to l-galactose-1-P, thus catalyzing the first committed step in the biosynthesis of l-ascorbate. Here we report that the l-galactose pathway of ascorbate biosynthesis described in higher plants is conserved in green algae. The Chlamydomonas reinhardtii genome encodes all the enzymes required for vitamin C biosynthesis via the Smirnoff-Wheeler pathway. We have characterized recombinant C. reinhardtii VTC2 as an active GDP-l-galactose phosphorylase. C. reinhardtii cells exposed to oxidative stress show increased VTC2 mRNA and l-ascorbate levels. We have also shown that enzymatic components of the ascorbate-glutathione system (e.g. ascorbate peroxidase, Mn superoxide dismutase, dehydroascorbate reductase) are up-regulated in response to increased oxidative stress. These results indicate that C. reinhardtii VTC2, like its plant homologs, is a key enzyme in ascorbate biosynthesis in green algae and together with components of the ascorbate recycling system represents the major route in providing protective levels of ascorbate in oxidatively stressed algal cells. Our results suggest that C. reinhardtii cells exposed to oxidative stress conditions produce more ascorbate both by de novo synthesis (Smirnoff-Wheeler pathway) and by recycling via the ascorbate-glutathione cycle.
2012-05-03 | GSE34826 | GEO
Project description:We explore where transcriptional regulation of ascorbate concentration lies in plants. Is it in biosynthesis, recycling, regulation or consumption? Arabidopsis thaliana plants were grown under controlled environment at four photon flux density levels (PFD). Rosettes from plants were harvested at the four PFD levels and over a diurnal cycle and after a step change in PFD and analysed for ascorbate concentration and transcript levels measured by RNAseq. Ascorbate concentrations and expression of genes in the L-galactose ascorbate biosynthesis, recycling, consumption pathways and regulation are presented to provide a full analysis of the control of ascorbate by environmentally modulated gene expression. Ascorbate concentration responded to PFD levels but not to time of day and showed only a small response to change of PFD after 2 days. Of the L-galactose pathway genes, only GDP galactose phosphorylase (GGP) showed a significant response in to different PFDs, time of day and to change in PFD. Other genes also showed limited responses. This study compares gene expression of a range of ascorbate related genes to changes in environment in a unified way and supports the concept that GGP is the key regulatory gene in ascorbate biosynthesis and that post transcriptional regulation is also important.
2017-02-17 | GSE94995 | GEO
Project description:RNA populations in Chlamydomonas reinhardtii Keywords: Highly parallel pyrosequencing
2007-05-16 | GSE7308 | GEO
Project description:Linear tetrapyrrole (bilin)-based phytochrome sensors optimize photosynthetic light capture by mediating massive gene reprogramming in land plants, yet surprisingly, many sequenced chlorophyte (green) algae lack phytochrome genes. Previous studies on the heme oxygenase (hmox1) mutant of Chlamydomonas reinhardtii suggest that bilin biosynthesis in plastids is needed for regulation of a limited nuclear gene network implicated in oxygen detoxification during dark to light transitions. The hmox1 mutant is unable to grow photoautotrophically and poorly acclimates to increased illumination even in the presence of acetate. Here we show that these phenotypes reflect the reduced accumulation of PSI reaction centers as well as a loss of PSI and PSII antennae complexes during photoacclimation. Phenotypically, the hmox1 mutant is similar to the chlorophyll biosynthesis mutants, gun4, crd1 and cth1. However, many of the hmox1 phenotypes can be rescued by the application of exogenous biliverdin IXα, the bilin product of HMOX1; this rescue is independent of photosynthesis but strongly dependent upon blue light. RNA-Seq comparisons of hmox1, 4A+ wild type and two genetically complemented lines also reveal that bilins restore regulation of a small network of photosynthesis-associated nuclear genes. These include genes responsible for chlorophyll biosynthesis (CHLI1/2), PSI light-harvesting (LHCA4) and naphthoquinone metabolism (MEN2), all of which show reduced photoinduction in the hmox1 mutant. We propose that a bilin-based, blue light sensory system is responsible for the maintenance of a functional photosynthetic apparatus in light-grown C. reinhardtii. This critical and possibly ancestral role for bilins may be responsible for retention of bilin biosynthesis in all eukaryotic photosynthetic species.
2019-01-24 | GSE77388 | GEO
Project description:RNA populations in Chlamydomonas reinhardtii Keywords: Highly parallel pyrosequencing Small RNAs were prepared from Chlamydomonas reinhardtii total extracts,ligated to a 3' adaptor and a 5' acceptor sequentially, and then RT-PCR amplified. PCR products were reamplified using a pair of 454 cloning primers and provided to 454 Life Sciences (Branford, CT) for sequencing. For technical details, see Tao Zhao, Guanglin Li, Shijun Mi, Shan Li, Gregory J. Hannon, Xiu-Jie Wang, and Yijun Qi. 2007. A Complex System of Small RNAs in the Unicellular Green Alga Chlamydomonas reinhardtii. Genes & Development
2007-05-15 | E-GEOD-7308 | biostudies-arrayexpress
Project description:Chlamydomonas reinhardtii exposed to various concentrations of silver
2013-10-01 | GSE48677 | GEO
Project description:Comparison of gene expression for Chlamydomonas cells grown for 0h, 48h, 72h, 96h in sulfur depleted media
2014-09-08 | E-MTAB-1329 | biostudies-arrayexpress
Project description:Chlamydomonas reinhardtii forms lipid droplets rich in triacylglycerols when nutrient-deprived. To begin studying the mechanisms underlying this process, N-deprivation was used to induce triacylglycerol accumulation and changes in developmental programs such as gametogenesis. Comparative global analysis of transcripts under induced and non-induced conditions was applied as a first approach to study molecular changes that promote or accompany triacylglycerol accumulation in cells encountering a new nutrient environment. Towards this goal, high-throughput sequencing technology was employed to generate large numbers of expressed sequence tags of 8 biologically independent libraries (6 Illumina libraries, 2 454 libraries), four for each condition, N-replete and N-deprived, that allowed a statistically sound comparison of expression levels under the two tested conditions. Inferences on metabolism based on transcriptional analysis can only be indirect but were supported in parts by biochemical experiments. N-deprivation led to a marked redirection of metabolism as the carbon source acetate was no longer converted to cell building blocks by the glyoxylate cycle and gluconeogensis, but funneled directly into fatty acid biosynthesis. Protein biosynthesis and photosynthesis were down-regulated and genes of gametogenesis activated. A notable finding was that the genes encoding photosynthetic accessory PSBS proteins of currently unclear function in C. reinhardtii were strongly expressed following N-deprivation, providing a clue to their physiological role. Lipase-encoding genes were found to be some of the most regulated following N-deprivation, suggesting a remodeling of membranes under these conditions. The data provided here represent a rich source for the exploration of the mechanism of oil accumulation in microalgae. Examining N-replete and N-deprived conditions. Three biological replicates each condition.
2010-09-24 | E-GEOD-24365 | biostudies-arrayexpress
Project description:Phosphorus (P) is an essential nutrient that is limiting in many environments. When P is scarce organisms employ strategies for conservation of internal stores, and to efficiently scavenge P from their external surroundings. In this study we investigated the acclimation response of Chlamydomonas reinhardtii to P deficiency, comparing the transcriptional profiles of P starved wild-type cells to the P replete condition. RNA was prepared from P-containing or P-deprived logarithmic growth phase cells and subjected to RNA-Seq analysis. During the 24 hours after the imposition of P starvation we observed that from the 407 significantly changing genes (> 2 fold change, corrected p-value < 0.05) in the wild-type 317 genes were up-regulated, in average 8.36-fold, and 90 genes were down-regulated by 3.43-fold, in average. Many of the upregulated genes encoded enzymes involved in specific responses to P starvation, including PHOX, encoding the major secreted alkaline phosphatase, and multiple putative, high-efficiency phosphate transporter genes. More general responses included the up-regulation of genes involved in photoprotective processes (LHCSR3, LHCSR1, LHCBM9, PTOX1) and genes involved in protein modification and degradation. Down-regulated mRNAs indicated an early stage of the reduction of chloroplast ribosomal proteins, which are considered to be a reservoir for P in the cell.
2014-04-05 | GSE56505 | GEO