Since pepc gene encoding phosphoenolpyruvate carboxylase （PEPCase） has been cloned from Anabaena sp. PCC 7120 and other cyanobacteria, the effects of pepc gene expression on photosynthesis have not been reported yet...Since pepc gene encoding phosphoenolpyruvate carboxylase （PEPCase） has been cloned from Anabaena sp. PCC 7120 and other cyanobacteria, the effects of pepc gene expression on photosynthesis have not been reported yet. In this study, we constructed mutants containing either upregu-lated （forward） or downregulated （reverse） pepc gene in Anabaena sp. PCC 7120. Results from real‐time quantitative polymerase chain reaction （RT‐qPCR）, Western blot and enzymatic analysis showed that PEPCase activity was signifi-cantly reduced in the reverse mutant compared with the wild type, and that of the forward mutant was obviously increased. Interestingly, the net photosynthesis in both the reverse mutant and the forward mutant were higher than that of the wild type, but dark respiration was decreased only in the reverse mutant. The absorbance changes of P700 upon saturation pulse showed the photosystem I （PSI） activity was inhibited, as reflected by Y（I）, and Y（NA） was elevated, and＆amp;nbsp;dark reduction of P700t was stimulated, indicating enhanced cyclic electron flow （CEF） around PSI in the reverse mutant. Additional y, the reverse mutant photosynthesis was higher than that of the wild type in low temperature, low and high pH, and high salinity, and this implies increased tolerance in the reverse mutant through downregulated pepc gene.展开更多
基金supported by the National High-tech R&D Program (863 Program) (Nos.2009AA064401 and 2014AA093506)National Administration Project from Chinese Ministry of Environmental Protection (No.04)supported by Shanghai Universities First-class Disciplines Project of Fisheries
文摘Since pepc gene encoding phosphoenolpyruvate carboxylase （PEPCase） has been cloned from Anabaena sp. PCC 7120 and other cyanobacteria, the effects of pepc gene expression on photosynthesis have not been reported yet. In this study, we constructed mutants containing either upregu-lated （forward） or downregulated （reverse） pepc gene in Anabaena sp. PCC 7120. Results from real‐time quantitative polymerase chain reaction （RT‐qPCR）, Western blot and enzymatic analysis showed that PEPCase activity was signifi-cantly reduced in the reverse mutant compared with the wild type, and that of the forward mutant was obviously increased. Interestingly, the net photosynthesis in both the reverse mutant and the forward mutant were higher than that of the wild type, but dark respiration was decreased only in the reverse mutant. The absorbance changes of P700 upon saturation pulse showed the photosystem I （PSI） activity was inhibited, as reflected by Y（I）, and Y（NA） was elevated, and＆amp;nbsp;dark reduction of P700t was stimulated, indicating enhanced cyclic electron flow （CEF） around PSI in the reverse mutant. Additional y, the reverse mutant photosynthesis was higher than that of the wild type in low temperature, low and high pH, and high salinity, and this implies increased tolerance in the reverse mutant through downregulated pepc gene.
