Analysis of thylakoid membrane protein and photosynthesis-related key enzymes in super high-yield hybrid rice LYPJ grown in field condition during senescence stage

A proteomic analysis combining photosynthesis-related key enzymes measurement and mRNA level analysis was used to investigate the variations of proteins involved in the photosynthetic apparatus in flag leaves of high-yield rice LYPJ during senescence under field conditions. The stability of chlorophyll-protein complexes of thylakoid membranes was measured by BN-PAGE system. Our findings revealed that the LHCII complexes were more stable than F0F1-ATPase and Cyb(6)/f complexes. Thylakoid membranes proteins during the senescence stage were separated by two-dimensional gel electrophoresis. We identified 13 photosynthesis-related proteins (a fivefold or greater variation), including electron transport, Calvin-Benson cycle and chloroplast protease during senescence of flag leaves. Moreover, our data showed that Ca2+-ATPase was more stable during senescence of flag leaves in rice, compared to Mg2+-ATPase. In enzymes activities analyses, it was observed that a little increment of C4 photosynthetic enzymes activities at the beginning of flag leaves senescence might compensate, to some degree, for the larger reductions in Rubisco activity, confirmed by quantitative RT-PCR analysis.