Differential Expression and Function Analysis of Proteins in Flag Leaves of Rice During Grain Filling

To investigate the molecular mechanism of metabolism in rice (Oryza sativa L.) source organs, protein expression pattern in flag leaves of rice cultivar Jinhui 809, a cultivar with large panicle and high seed-setting percentage, was analyzed during grain-filling period. Using two-dimensional electrophoresis and mass spectrometry, 17 protein spots with differential expression were detected. Among them, 3 protein spots had the most expression amount from early to medium stage, 9 protein spots for middle–late stages, and 4 protein spots for late stage. In addition, 1 protein spot had two-expression peaks at early and late stages of grain filling. Twelve differential proteins were identified with MALDI-TOF/MS analysis and database searching. They were involved in biosynthesis and degradation, carbohydrate transportation, antioxidation reaction, hormone metabolism, cytoskeleton construction, and tissue maturation. Ribose/galactose/methyl galactoside importing ATP-binding protein 1 participated in photosynthate transportation from leaf to grain in early and medium stages. Auxin-responsive protein IAA27 influenced photosynthate transportation through regulating the activity of ATPase. N-acetyl-glutamate semialdehyde dehydrogenase delayed leaf senescence through regulating polyamine metabolism in late stage. In addition, glutathione S-transferase and superoxide dismutase played an important role in plant detoxification and fighting against active oxygen damage at late stage of grain filling.