A molecular framework of the Rht-A1-TaLA1-D module controlling tiller angle in wheat.

Abstract

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-A1^ta1 variant acquires enhanced protein stability, whereas TaLA1-D^ta2 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-D^Hap1 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.