Analysis of Differential Expression of Proteins in Rice Leaf Sheath During Grain Filling

To reveal the molecular mechanism of metabolism in rice (Oryza sativa L.) leaf sheath, differential expression of proteome in rice leaf sheath was investigated with a large panicles and high grain-setting rate cultivar, i.e., Jinhui 809. Through the method of differential proteomics, 23 proteins were detected, and 11 proteins were identified to be the functional proteins. These functional proteins were classified into 6 categories according to their dynamic patterns of expression during grain-filling stage. The first class, such as oxaloacetate decarboxylase alpha subunit, showed down-regulation during grain filling. The second class, which included ribulose bisphosphate carboxylase small chain and ADP-ribosylation factor 1, exhibited up-regulation at first and then down-regulation. The third class, such as auxin response factor, zinc finger, C3HC4 type family protein, vacuolar proton-ATPase, and ribulose bisphosphate carboxylase/oxygenase activase, was down-regulation first and then up-regulation and down-regulation alternatively. The fourth class included Rubisco binding-protein alpha subunit, showing an expression pattern of up and down-regulation alternatively twice during grain filling. The fifth class performed a decreasing at first and then gradually increasing expression pattern. This class included class II metallothionein-like protein 1A and geranylgeranyl diphosphate synthase. The sixth class was protein kinase family protein performing a gradually increasing expression pattern. These 6 classes of proteins were involved in photosynthesis, hormone regulation, substance transportation, resistant response to plant senescence, and cell signal transduction in leaf sheath, respectively. They regulated the transition of sink to source together.