Project description:We used Chlamydomonas microarray v2.0 to compare the time course expression profiles of two Chlamydomonas reinhardtii strains: wild-type WT and the high hydrogen producing mutant Stm6Glc4 during sulfur starvation induced hydrogen production. Major cellular reorganizations in photosynthetic apparatus, sulfur and carbon metabolism upon H2 production were confirmed as common to both strains. More importantly, our results pointed out factors which lead to the higher hydrogen production in the mutant including higher light sensitivity and lower competitions with hydrogenase by alternative electron sinks. Under S-starvation induced H2 producing conditions the induction of LHCSR3, a chlorophyll binding protein involving in non photochemical quenching, was significantly lower in Stm6Glc4 resulting in significant higher photodamage to photosystem II. Consequently, Stm6Glc4 had a shorter aerobic phase, consumed less starch reserves, and produced H2 earlier at higher rates than WT. We also showed that the loss of mitochondrial DNA-binding protein MOC1 in both knockdown and knockout mutant resulted in higher light sensitivity and improved H2 yield. Furthermore, by comparing our data with previously published ‘omics’ data, we were able to identify genes that responded specifically to either sulfur starvation, anaerobiosis or hydrogen production as well as to provide a more complete picture of S-deprived H2 production in the green alga C. reinhardtii. A total of 33 microarray hydridizations were performed covering samples taken during the course of S deprivation induced H2 producction. The samples included 4 time points in the high hydrogen producing mutant Stm6Glc4 (taken at 16, 28, 52 and 76h) and 6 time points in the wildtype CC-406 (taken at 16, 28, 52, 68, 92, 116h). Samples from each time point were compared directly with the sample taken prior to S starvation from the corresponding strain. Three biological replicates were tested at each time point.

Project description:Responses of photosynthetic organisms to sulfur starvation include (i) increasing the capacity of the cell for transporting and/or assimilating exogenous sulfate, (ii) restructuring cellular features to conserve sulfur resources, and (iii) modulating metabolic processes and rates of cell growth and division. We used microarray analyses to obtain a genome-level view of changes in mRNA abundances in the green alga Chlamydomonas reinhardtii during sulfur starvation. The work confirms and extends upon previous findings showing that sulfur deprivation elicits changes in levels of transcripts for proteins that help scavenge sulfate and economize on the use of sulfur resources. Changes in levels of transcripts encoding members of the light-harvesting polypeptide family, such as LhcSR2, suggest restructuring of the photosynthetic apparatus during sulfur deprivation. There are also significant changes in levels of transcripts encoding enzymes involved in metabolic processes (e.g., carbon metabolism), intracellular proteolysis, and the amelioration of oxidative damage; a marked and sustained increase in mRNAs for a putative vanadium chloroperoxidase and a peroxiredoxin may help prolong survival of C. reinhardtii during sulfur deprivation. Furthermore, many of the sulfur stress-regulated transcripts (encoding polypeptides associated with sulfate uptake and assimilation, oxidative stress, and photosynthetic function) are not properly regulated in the sac1 mutant of C. reinhardtii, a strain that dies much more rapidly than parental cells during sulfur deprivation. Interestingly, sulfur stress elicits dramatic changes in levels of transcripts encoding putative chloroplast-localized chaperones in the sac1 mutant but not in the parental strain. These results suggest various strategies used by photosynthetic organisms during acclimation to nutrient-limited growth. An all pairs experiment design type is where all labeled extracts are compared to every other labeled extract. Keywords: all_pairs

Project description:Responses of photosynthetic organisms to sulfur starvation include (i) increasing the capacity of the cell for transporting and/or assimilating exogenous sulfate, (ii) restructuring cellular features to conserve sulfur resources, and (iii) modulating metabolic processes and rates of cell growth and division. We used microarray analyses to obtain a genome-level view of changes in mRNA abundances in the green alga Chlamydomonas reinhardtii during sulfur starvation. The work confirms and extends upon previous findings showing that sulfur deprivation elicits changes in levels of transcripts for proteins that help scavenge sulfate and economize on the use of sulfur resources. Changes in levels of transcripts encoding members of the light-harvesting polypeptide family, such as LhcSR2, suggest restructuring of the photosynthetic apparatus during sulfur deprivation. There are also significant changes in levels of transcripts encoding enzymes involved in metabolic processes (e.g., carbon metabolism), intracellular proteolysis, and the amelioration of oxidative damage; a marked and sustained increase in mRNAs for a putative vanadium chloroperoxidase and a peroxiredoxin may help prolong survival of C. reinhardtii during sulfur deprivation. Furthermore, many of the sulfur stress-regulated transcripts (encoding polypeptides associated with sulfate uptake and assimilation, oxidative stress, and photosynthetic function) are not properly regulated in the sac1 mutant of C. reinhardtii, a strain that dies much more rapidly than parental cells during sulfur deprivation. Interestingly, sulfur stress elicits dramatic changes in levels of transcripts encoding putative chloroplast-localized chaperones in the sac1 mutant but not in the parental strain. These results suggest various strategies used by photosynthetic organisms during acclimation to nutrient-limited growth. An all pairs experiment design type is where all labeled extracts are compared to every other labeled extract. Computed

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Chlamydomonas reinhardtii

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