Dataset Information

Time-course global expression profiles of Chlamydomonas reinhardtii during photo-biological H? production.

ABSTRACT: We used a microarray study in order to compare the time course expression profiles of two Chlamydomonas reinhardtii strains, namely the high H? producing mutant stm6glc4 and its parental WT strain during H? production induced by sulfur starvation. Major cellular reorganizations in photosynthetic apparatus, sulfur and carbon metabolism upon H? production were confirmed as common to both strains. More importantly, our results pointed out factors which lead to the higher H? production in the mutant including a higher starch accumulation in the aerobic phase and a lower competition between the H?ase pathway and alternative electron sinks within the H? production phase. Key candidate genes of interest with differential expression pattern include LHCSR3, essential for efficient energy quenching (qE). The reduced LHCSR3 protein expression in mutant stm6glc4 could be closely related to the high-light sensitive phenotype. H? measurements carried out with the LHCSR3 knock-out mutant npq4 however clearly demonstrated that a complete loss of this protein has almost no impact on H? yields under moderate light conditions. The nuclear gene disrupted in the high H? producing mutant stm6glc4 encodes for the mitochondrial transcription termination factor (mTERF) MOC1, whose expression strongly increases during -S-induced H? production in WT strains. Studies under phototrophic high-light conditions demonstrated that the presence of functional MOC1 is a prerequisite for proper LHCSR3 expression. Furthermore knock-down of MOC1 in a WT strain was shown to improve the total H? yield significantly suggesting that this strategy could be applied to further enhance H? production in other strains already displaying a high H? production capacity. By combining our array data with previously published metabolomics data we can now explain some of the phenotypic characteristics which lead to an elevated H? production in stm6glc4.

SUBMITTER: Nguyen AV

PROVIDER: S-EPMC3248568 | biostudies-literature | 2011

REPOSITORIES: biostudies-literature

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Time-course global expression profiles of Chlamydomonas reinhardtii during photo-biological H₂ production.

Nguyen Anh Vu AV Toepel Joerg J Burgess Steven S Uhmeyer Andreas A Blifernez Olga O Doebbe Anja A Hankamer Ben B Nixon Peter P Wobbe Lutz L Kruse Olaf O

PloS one 20111229 12

We used a microarray study in order to compare the time course expression profiles of two Chlamydomonas reinhardtii strains, namely the high H₂ producing mutant stm6glc4 and its parental WT strain during H₂ production induced by sulfur starvation. 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 H₂ production in the mutant ...[more]

PMID: 22242116

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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. Time course microarray analyses were used to analyze the global gene expression in sulfur depleted hydrogen producing C. reinhardtii. When depleted of sulfur, a sealed an illuminated C. reinhardtii culture slowly becomes anaerobic and produces hydrogen gas. Based on the changes in the dissolved O2 level and H2 production rate, the whole course of H2 production from the starting of S deprivation to the end of H2 production can be divided into five phases including an Aerobic Phase (I) in which the dissolved O2 level goes up (I), an O2 Consumption Phase (II), an Anaerobic Phase (III), a H2 Production Phase (IV) and a Termination phase (V). Samples were taken from three different bioreactors (biological replicates) at the following time points after the start of S depletion: 6 h, 16 h, 21 h, 37 h and 52 h corresponding to Peak O2, Mid O2, Zero O2, Mid H2 and Peak H2.

Dataset Information

Time-course global expression profiles of Chlamydomonas reinhardtii during photo-biological H? production.

Publications

Time-course global expression profiles of Chlamydomonas reinhardtii during photo-biological H₂ production.

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