Sucrose signaling regulates storage protein synthesis in maize endosperm

Sucrose plays a crucial role as a primary carbon source during seed development. In addition to this metabolic function, sucrose and its breakdown products (hexoses) serve as important signaling molecules that regulate cell fate and seed development in maize. However, the precise molecular mechanisms through which sucrose influences storage protein synthesis during seed development remain poorly understood. In this study, we identified a novel allelic mutant of Incw2, named vitreous endosperm 2 (ven2). The loss-of-function mutation in Incw2 led to a significant reduction in grain weight, accompanied by a marked increase in sucrose levels in the basal endosperm. This was also associated with substantial increases in the accumulation of the 19 kDa and 22 kDa α-zein proteins. In contrast, overexpression of Incw2 resulted in lower sucrose and zein contents. Furthermore, we discovered that the transcription factor Sugar Response Factor 1 (SRF1), which is responsive to sucrose, regulates the expression of the 19 kDa and 22 kDa α-zein genes by directly binding to their promoters. These findings suggest that disruption of sucrose metabolism due to the Incw2 mutation modulates α-zein gene expression and affects protein synthesis during seed development.