Identification of a co-segregative protein associated with the tillering trait in rice (Oryza sativa L.)

Tillering is an important trait for grain production in rice. To understand the mechanism underlying tillering regulation in rice, a combined proteomic and genetic approach was taken to analyze potential protein markers associated with the high-tillering dwarf phenotype. Total proteins were extracted from basal internodes of rice plants and subjected to 2-dimensional gel electrophoresis. Proteomes were compared between control rice cultivars and tillering mutant lines that are known to have a reduced number of culms or contain the d10 allele. A total of 33 polymorphic protein markers were identified between the wild-type cultivar GLA4 and the mutant line JHCA with dwarf and high tillering phenotype. A protein spot was found to behave as a qualitative trait, cosegregating with the normal-tillering phenotype in the F-2 population. This protein was present in the wild-type plants, but was undetectable in the mutant line JHCA and the high-tillering dwarf F-2 plants. Mass spectrometry analysis identified the protein as putative carboxyvinyl-carboxyphosphonate phosphorylmutase (CPPM; EC 2.7.8.23), which may catalyze the formation of a unique C-P bond from phosphoenolpyruvate and may participate in the biosynthesis of unidentified compounds with an inhibitory effect on tillering in rice. Real-time PCR analysis revealed that the mRNA level of CPPM was down-regulated in the high-tillering d10 dwarf plants, suggesting that the expression of the CPPM gene requires the function of D10. We propose that CPPM may play a role that is related to the tillering regulation in rice.