Ectopic Expression of the Transcriptional Regulator silky3 Causes Pleiotropic Meristem and Sex Determination Defects in Maize Inflorescences

Abstract

Maize (Zea mays) is a monoecious plant, in which inflorescence morphogenesis involves complicated molecular regulatory mechanisms. Although many related genes have been cloned, our understanding of the molecular mechanism underlying maize inflorescence development remains limited. Here, we identified a maize semi-dominant mutant Silky3 (Si3), which displays pleiotropic defects during inflorescence development, including loss of determinacy and identity in meristems and floral organs, as well as the sexual transformation of tassel florets. We cloned the si3 gene using a map-based approach. Functional analysis reveals that SI3 is a nuclear protein and may act as a transcriptional regulator. Transcriptome analysis reveals that the ectopic expression of si3 strongly represses multiple biological processes, especially the flower development pathways. RNA in situ hybridization similarly shows that the expression patterns of genes responsible for flower development are changed in the Si3 mutant. In addition, the homeostasis of jasmonic acid and gibberellic acid are altered in the Si3 young tassels, and application of exogenous jasmonic acid can rescue the sex reversal phenotype of Si3. The defects we characterized in various regulatory pathways can explain the complex phenotypes of Si3 mutant, and this study deepens our knowledge of maize inflorescence development.