Maize transcription factor ZmEREB167 negatively regulates starch accumulation and kernel size.

Abstract

Transcription factors play critical roles in the regulation of gene expression during maize kernel development. The maize endosperm is a large storage organ, accounting for nearly 90% of the dry weight of mature kernel, and is also the main place for starch storage. In this study, we identify an endosperm-specific EREB gene, ZmEREB167, which encodes a nucleus-localized EREB protein. Knockout of ZmEREB167 significantly increases kernel size and weight, as well as the starch and protein content compared with wild type kernels. In situ hybridization experiments show that ZmEREB167 is highly expressed in the BETL as well as PED regions of maize kernels. Dual-luciferase assay show that ZmEREB167 exhibits transcriptionally inhibitory function in maize protoplasts. Transcriptome analysis reveals that a large number of genes were up-regulated in zmereb167-C1 mutant compared with wild type, including the key genetic factors of ZmMRP-1 and ZmMN1, and numbers of transporters during maize endosperm development. Overlay of the RNA-seq and ChIP-seq results reveals 68 ZmEREB167-modulated target genes. We find that ZmEREB167 directly targets OPAQUE2, ZmNRT1.1, ZmIAA12, ZmIAA19, and ZmBIZP20, and repressed their expression. Our study reveals that ZmEREB167 functions as a negative regulator in maize endosperm development and affects the starch accumulation and kernel size.