Tiller angle is a critical determinant of wheat plant architecture, which profoundly impacts yield potential. However, the regulatory mechanisms of tiller angle in wheat remain largely unexplored. To explore the underlying mechanisms, we identify two EMS-mutagenized wheat mutants tiller angle 1 (ta1) and ta2 with enlarged tiller angles. Molecular characterization reveals that TA1 and TA2 encode the DELLA protein Rht-A1 and TaLA1-D, respectively. Biochemical analyses demonstrate that the Rht-A1ta1 variant acquires enhanced protein stability, whereas TaLA1-Dta2 exhibits destabilization. We establish a mechanistic framework that Rht-A1 physically associates with TaPROG1 to synergistically repress TaLA1-D transcription. Moreover, we show that TaGSK3 directly interacts with and phosphorylates TaLA1-D to enhance its stability in reducing wheat tiller angles. Population genomic analyses uncover a significant selection for the elite TaLA1-DHap1 allele during modern wheat breeding, correlating with compact plant architecture and elevated thousand-grain weight. This study provides new insights into plant architecture regulation and target genes for improving yield potential in wheat. This study identifies a Rht-A1–TaLA1-D module controlling wheat tiller angle, elucidates its mechanism, and traces the selection trajectory of TaLA1-D during wheat breeding, providing new insights for developing ideotype wheat varieties.
Chen et al. (Tue,) studied this question.