A Proteomic Approach to Analyze Differential Regulation of Proteins During Bud Outgrowth Under Apical Dominance Based on the Auxin Transport Canalization Model in Rice (Oryza sativa L.)

Apical dominance refers to the inhibition of shoot branching by the dominant shoot apex. The underlying mechanisms of apical dominance, especially in rice (Oryza sativa), remain a subject of debate. Here, we studied apical dominance in the indica rice variety 'Yangdao 6' and carried out a comparative proteomic analysis to analyze the different levels of expression of proteins after decapitation. A total of 38 differentially expressed proteins in nodes and buds were successfully identified by MALDI-TOF/TOF and these proteins comprised ten functional categories. Among them, several proteins in this study involved in signal transduction, transporters, and cytokinin biosynthesis may play an important role in the mechanism of apical dominance. In addition, qRT-PCR was used to quantitate the expression levels of several genes in rice nodes and buds. The results showed that after decapitation, the expression level of a CK synthesis gene, OsLOG7, was reduced in buds, however, expression levels of several CK synthesis genes, OsIPTs, were markedly increased in nodes, indicating that after panicle removal, cytokinins were synthesized in nodes and subsequently delivered to buds, which will trigger release from dormancy in buds. Expression levels of several strigolactone-related genes were reduced in nodes after decapitation, which may become a factor facilitating auxin transport out of buds to stems.