Peizhou Xu, Asif Ali , Yun Li, Hongyu Zhang, Xiaoqiong Chen, Shaohong Fu, Jin Yang, Zhongwei Zhang, Shu Yuan, Xianjun Wu
Homeotic mutations can affect the genetic architecture of flower structure. Some genes have been identified that specify shoot and floral meristem development. ABCDE and floral quartet are two widely accepted models that explain how genes interact to form all the whorls of a flower. In the current study, we identified an spp1 (SUPER PISTIL 1) mutant controlled by a single recessive nuclear gene mapping to chromosome 6 near RM50. Compared to wild type, spp1 mutants showed similar agronomic traits, except for panicle length and 1000-grain weight, which were significantly lower in the spp1 mutant plants. The mutation in the SPP1 gene induced complete homeotic transformations of paleae, lodicules, and stamens into carpelloid structures. Although lemmata were only marginally affected in the spp1 mutants, they developed a stigma-like structure on the top instead of an awn. Interestingly, stigma-like structures were also observed at the base of panicle branches. From the results, we propose that the SPP1 gene plays an important role in specifying the identity of lemmata/paleae, lodicules, stamens, and inflorescence meristem in rice. Identification of this mutant not only provides further evidence for validity of the ABCDE model in monocots, but also contributes to the understanding of meristem development.