Project description:This SuperSeries is composed of the following subset Series: GSE33039: replication experiment GSE33040: Sulfur starvation experiment in Chlamydomonas GSE33041: Chlamydomonas growth under nitrogen starvation Refer to individual Series
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.
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:Algal photo-bio hydrogen production, a promising method for producing clean and renewable fuel in the form of hydrogen gas, has been studied extensively over the last few decades. In this study, microarray analyses were used to obtain a global expression profile of mRNA abundance in the green alga Chlamydomonas reinhardtii at five different time points before the onset and during the course of sulphur depleted hydrogen production. The present work confirms previous findings on the impacts of sulphur deprivation but also provides new insights into photosynthesis, sulphur assimilation and carbon metabolism under sulphur starvation towards hydrogen production. For instance, while a general trend towards repression of transcripts encoding photosynthetic genes was observed, the abundance of Lhcbm9 (encoding a major light harvesting polypeptide) and LhcSR1 (encoding a chlorophyll binding protein) was strongly elevated throughout the experiment, suggesting remodeling of the photosystem II light harvesting complex as well as an important function of Lhcbm9 under sulphur starvation. This study presents the first global transcriptional analysis of C. reinhardtii during hydrogen production using five major time points at Peak Oxygen, Mid Oxygen, Zero Oxygen, Mid Hydrogen and Peak Hydrogen. Keywords: Time course, sulfur deprivation, hydrogen production.
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.
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