Yunchuan Liu, Mingming Wang, Yaojia Wang, Haixia Liu, Wei Xi, David Seung, Xiaolu Wang, Lei Zhuang, Huifang Li, Tian Li, Hongxia Liu, Jian Hou, Xu Liu, Chenyang Hao, Xueyong Zhang

Molecular Plant; 2025; 24.1

DOI:10.10.16/j.molp.202506.007

Abstract

Starch is the principal storage compound in wheat grain, essential for flour quality and grain weight. In this study, we identified TaMYB44, an R2R3-MYB transcription factor gene, through a genome-wide association study. The TaMYB44 homoeologs exhibited predominant expression in developing grains, with peak levels observed at 10 days after pollination. Functional analyses revealed that TaMYB44 acts as a negative regulator of starch synthesis in the endosperm and limits grain size by repressing starch synthesis-related genes and modulating secondary metabolism. Knockout mutants of TaMYB44 exhibited significantly increased starch accumulation, larger grain size, and enhanced yield stability across different growing environments. Additionally, we discovered that TaWDR1 interacts with TaMYB44, alleviating its repressive effects to restore starch synthesis and enhance grain weight. Moreover, we found that the functions of MYB44 are partially conserved in both wheat and rice, underscoring its potential as a target for genetic improvement. Our findings provide valuable insights into the transcriptional regulation of starch synthesis and present genetic resources for improving grain yield in wheat and rice.