ZmMYB127 Modulates Maize Kernel Texture and Size by Integrating the Synthesis of Starch, Zein Proteins and Auxin.

Kernel texture is an important agronomic trait that determines the end-uses of maize kernels and affects their integrity at harvest and susceptibility to pests and diseases. The ratio of the vitreous endosperm (RVE) is the key index for assessing kernel texture, and identifying key genes involved in its formation is crucial for maize breeding. Here, through genome-wide association study (GWAS), haplotype analysis and transgenic kernels phenotyping, we characterised ZmMYB127, an endosperm-specific R2R3-MYB transcription factor, which positively regulates vitreous endosperm (VE) formation. ZmMYB127 is preferentially expressed in VE cells during the filling stage and antagonistically regulates zein protein and starch synthesis in the endosperm. Notably, ZmMYB127 interacts with OPAQUE2 (O2) to synchronously transactivate genes encoding α-zein proteins and interacts with prolamin-box binding factor 1 (PBF1) to additively suppress genes involved in starch synthesis, thereby governing kernel texture. Moreover, ZmMYB127 negatively regulates genes involved in indole-3-acetic acid (IAA) synthesis in the endosperm, affecting endosperm development and size, thereby linking the function of ZmMYB127 to kernel size. In conclusion, our study unravels the transcription factor ZmMYB127 that modulates kernel texture and size by integrating regulation of starch, zein and auxin synthesis pathways in maize endosperm. Additionally, our findings provide valuable genetic resources for breeding or engineering maize varieties with improved kernel texture and quality.