Natural Variation of TaSG-D1-TaWRKY53 Module Regulates Heading Date in Wheat

Heading date is a critical determinant of regional adaptation and yield potential. Here, we identify an E286K substitution in TaSG-D1, encoding an STKc_GSK3 kinase, which delays heading date in wheat. Mechanistically, this substitution strengthens the physical interaction between TaSG-D1 and TaWRKY53 and enhances the phosphorylation of TaWRKY53. Interestingly, the phosphorylation confers increased transcriptional activation of TaWRKY53 to the downstream gene VRN2. We further show that TaWRKY53 has been under artificial selection during Chinese wheat breeding. Modern cultivars frequently carry a premature stop codon in TaWRKY53, resulting in a 34 amino acid truncation relative to local landraces. This truncation eliminates phosphorylation of TaWRKY53 and impairs its transcriptional activity, which reduces VRN2 expression and ultimately accelerates heading. Our findings unveil a TaSG-D1-TaWRKY53 regulatory module controlling heading date and identify key genetic variants underlying wheat adaptation to the double-cropping system in China.