The genome of unicellular green alga Chlamydomonas reinhardtii contains four genes encoding B-type methionine sulfoxide reductases, MSRBI.1, MSRB1.2, MSRB2.1, and MSRB2.2, with functions largely unknown. To understand...The genome of unicellular green alga Chlamydomonas reinhardtii contains four genes encoding B-type methionine sulfoxide reductases, MSRBI.1, MSRB1.2, MSRB2.1, and MSRB2.2, with functions largely unknown. To understand the cell defense system mediated by the methionine suifoxide reductases in Chlamydomonas, we analyzed expression and physiological roles of the MSRBs under different abiotic stress conditions using immunoblotting and quantitative polymerase chain reaction (PCR) analyses. We showed that the MSRB2.2 protein was accumulated in cells treated with high light (1,300 μE-/m2 per s), whereas MSRBI.1 was accumulated in the cells under 1 mmol/L H2O2 treatment or sulfur depletion. We observed that the cells with the MSRB2.2 knockdown and overexpression displayed increased and decreased sensitivity to high light, respectively, based on in situ chlorophyll a fluorescence measures. We also observed that the cells with the MSRBI.1 knockdown and overexpression displayed decreased and increased tolerance to sulfur-depletion and oxidative stresses, respectively, based on growth and H2- producing performance. The physiological implications revealed from the experimental data highlight the importance of MSRB2.2 and MSRBI.1 in protecting Chlamydomonas cells against adverse conditions such as high-light, sulfur-depletion, and oxidative stresses.展开更多
Summary We have identified hpm91, a Chlamydomonas mutant lacking Proton Gradient Regulation5 (PGRS) capable of producing hydrogen (H2) for 25 days with more than 3o-fold yield increase compared to wild type. Thus,...Summary We have identified hpm91, a Chlamydomonas mutant lacking Proton Gradient Regulation5 (PGRS) capable of producing hydrogen (H2) for 25 days with more than 3o-fold yield increase compared to wild type. Thus, hpm91 displays a higher capacity of H2 production than a previously characterized pgr5 mutant. Physiological and biochemical characterization of hpm91 reveal that the prolonged H2 production is due to enhanced stability of PSII, which correlates with increased reactive oxygen species (ROS) scavenging capacity during sulfur depriva- tion. This anti-ROS response appears to protect the photosynthetic electron transport chain from photo- oxidative damage and thereby ensures electron supply to the hydrogenase.展开更多
基金supported by the Ministry of Science and Technology of China (2009CB220000)Chinese Ministry of Agriculture (2009ZX08009-121B)the Chinese Academy of Sciences
文摘The genome of unicellular green alga Chlamydomonas reinhardtii contains four genes encoding B-type methionine sulfoxide reductases, MSRBI.1, MSRB1.2, MSRB2.1, and MSRB2.2, with functions largely unknown. To understand the cell defense system mediated by the methionine suifoxide reductases in Chlamydomonas, we analyzed expression and physiological roles of the MSRBs under different abiotic stress conditions using immunoblotting and quantitative polymerase chain reaction (PCR) analyses. We showed that the MSRB2.2 protein was accumulated in cells treated with high light (1,300 μE-/m2 per s), whereas MSRBI.1 was accumulated in the cells under 1 mmol/L H2O2 treatment or sulfur depletion. We observed that the cells with the MSRB2.2 knockdown and overexpression displayed increased and decreased sensitivity to high light, respectively, based on in situ chlorophyll a fluorescence measures. We also observed that the cells with the MSRBI.1 knockdown and overexpression displayed decreased and increased tolerance to sulfur-depletion and oxidative stresses, respectively, based on growth and H2- producing performance. The physiological implications revealed from the experimental data highlight the importance of MSRB2.2 and MSRBI.1 in protecting Chlamydomonas cells against adverse conditions such as high-light, sulfur-depletion, and oxidative stresses.
基金supported by grants from the National Natural Science Foundation of China (No. 31470340 and No. 31270288)National Basic Research Program of China (973Program, No. 2015CB150100)+1 种基金CAS XDB (No. 17030300)the Foreign Expert Program (J-D.R.)
文摘Summary We have identified hpm91, a Chlamydomonas mutant lacking Proton Gradient Regulation5 (PGRS) capable of producing hydrogen (H2) for 25 days with more than 3o-fold yield increase compared to wild type. Thus, hpm91 displays a higher capacity of H2 production than a previously characterized pgr5 mutant. Physiological and biochemical characterization of hpm91 reveal that the prolonged H2 production is due to enhanced stability of PSII, which correlates with increased reactive oxygen species (ROS) scavenging capacity during sulfur depriva- tion. This anti-ROS response appears to protect the photosynthetic electron transport chain from photo- oxidative damage and thereby ensures electron supply to the hydrogenase.