Beyond dwarfism: Green Revolution gene Rht-D1b orchestrates tiller angle and canopy architecture in wheat

The Green Revolution genes Rht-B1b and Rht-D1b encode truncated DELLA proteins that confer gibberellin (GA)-insensitive semi-dwarfism in wheat. Their roles in reducing plant height and enhancing lodging resistance are well established, but their pleiotropic effects on specific components of plant architecture require further genetic dissection. Here, we reveal a previously unrecognized role of Rht-D1b in regulating tiller angle, a key determinant of canopy architecture. Quantitative trait locus (QTL) mapping identified Rht-D1b as a major locus controlling tiller angle. Functional validation showed that Rht-D1b not only reduces plant height but also increases tiller angle and tiller number, thereby optimizing canopy structure for enhanced yield potential. Transcriptome profiling indicated that Rht-D1b modulates the expression of genes involved in auxin signaling and polar auxin transport. Broad-scale phenotyping across diverse wheat accessions demonstrated that both Rht-B1b and Rht-D1b significantly increase tiller angle and leaf area index, with double mutants exhibiting the strongest effects on tiller architecture. Notably, the frequency of Rht-B1b and Rht-D1b has risen in modern cultivars, coinciding with a historical trend toward wider tiller angle. Together, these findings establish a novel pleiotropic role for the Green Revolution genes, demonstrating that they not only reduce plant height but also coordinate tiller angle and tiller number to optimize canopy architecture, ultimately elevating yield in wheat.