TaMYB72-B and TaGSK3 coordinately modulate wheat tillering through transcriptional and post-translational regulation of TN1

Tiller number is a pivotal agronomic trait directly determining grain yield in wheat (Triticum aestivum L.). Although TN1 is a key positive regulator of tillering, its regulatory network remains incompletely characterized. In this study, we identify TaMYB72-B and TaGSK3 as convergent regulators of TN1 that together fine-tune tiller number. Promoter analysis established TaMYB72-B as an upstream transcriptional repressor of TN1, and its overexpression reduced tiller number, confirming that TaMYB72-B suppresses tillering through TN1. Independently, the kinase TaGSK3 physically interacts with and phosphorylates TN1, destabilizing the protein and accelerating its degradation; overexpression of TaGSK3 likewise reduced tiller number significantly. Together, these findings define a dual-layer regulatory mechanism in which transcriptional repression and post-translational modification converge on TN1 to precisely control tiller development. Haplotype analysis across global wheat germplasm identified TaMYB72-B Hap 1 as an elite haplotype associated with an optimal balance between reduced tiller number and increased grains per spike, a combination that has been preferentially selected during modern breeding. This study, therefore, uncovers a novel regulatory module governing wheat tillering and offers actionable genetic targets for molecular design breeding aimed at optimizing plant architecture and yield.