A Gain-of-Function Mutation in DELLA Selectively Alters Protein Interactions to Regulate Wheat Tiller Angle and Plant Height.

Plant architecture, especially plant height and tiller angle, plays a pivotal role in determining wheat yield. In this study, we characterize a wheat mutant termed prostrate and semidwarf 1 (prose1), exhibiting both a prostrate growth habit and semidwarfism. Map-based cloning of the causal gene of prose1 identifies a semi-dominant mutation in Rht-A1-a homoeolog of the canonical Green Revolution genes-resulting in a glycine-to-glutamate substitution in the DELLA protein (designated Rht-A1h). The mutant protein displays enhanced physical interactions with tiller angle regulators including TaPROG1, TaLAZY1, TaLAZY4 and TaD14, while showing weakened interaction with TaHST1L. Consistently, overexpression of TaPROG1 phenocopies the enlarged tiller angle defect of prose1. We further demonstrate that Rht-A1h and TaPROG1 together repress their co-regulated downstream genes, exemplified by the shoot gravitropism-regulating TaWOX11. Knockout of TaWOX11 indeed recapitulates the enlarged tiller angle and defective shoot gravitropic response. A parallel study independently identified the same Rht-A1h mutation and its interaction with TaPROG1; our work provides complementary mechanistic insight by establishing TaWOX11 as a downstream target of this regulatory module. Together, our findings reveal a gain-of-function DELLA mutation that coordinates plant height and tiller angle through enhanced TaPROG1 interaction and TaWOX11 repression, and offer a genetic resource for fine-tuning wheat plant architecture in breeding.