Abstract
Active development of rachis branches leads to the production of more spikelets, and finally to generation of larger panicle. We identified a dominant mutant, APO1-D3, containing increased number of rachis branches and spikelets. APO1-D3 was caused by an insertion of an active transposon nDart1-0 in promoter region of APO1. The expression of APO1 was increased in APO1-D3, suggesting that APO1 regulates the transition timing from rachis branch meristem to spikelet meristem. The effect of APO1 on rachis branch development was confirmed by the APO1 over-expression (APO1ox) analysis. Approximately half of the APO1ox plants showed a hyper-branching phenotype with the severity in proportion to the APO1 expression level. In addition, the size of inflorescence meristem of APO1-D3 was enlarged compared with that of wild type. These results indicate that the expression level of APO1 regulates the panicle size through controlling cell proliferation in inflorescence meristem.
