The Ion Beam Crop Germplasm Creation and Utilization at the Institute of Intelligent Machines, Hefei Institute of Physical Science, Chinese Academy of Sciences, has identified a key molecular module that regulates rice plant architecture.
Their study was published in Plant Communications.
Rice tiller angle is an important trait that affects population structure, light utilization, planting density, and yield potential. While several genes affecting tiller angle have been reported, the upstream regulatory networks connecting gravity sensing and hormone distribution remained largely unknown.
Using heavy ion beam mutagenesis, the team identified a mutant, ita1, with a significantly increased tiller angle. Map-based cloning revealed a 740 bp deletion in the promoter of ITA1, a MYB transcription factor, resulting in its upregulation. Functional studies showed that ITA1 directly activates the expression of BRXL4, which regulates the localization of LAZY1 and the asymmetric distribution of auxin, weakening the plant' s gravitropic response. ITA1 also affects other auxin-related and developmental genes, such as OsIAA20, WOX6, and WOX11, highlighting its central role in tiller angle regulation.
Upstream, the transcription factor LPA1 binds to the ITA1 promoter to inhibit its expression, forming the LPA1-ITA1-BRXL4 regulatory module. Genetic analysis confirmed the hierarchical relationship between LPA1 and ITA1 in controlling tiller angle.
This discovery provides valuable genetic resources and regulatory modules for molecular breeding, enabling the design of ideal rice plant types and more precise control of crop architecture to improve population yield, according to the team.
Fig.1 Phenotypic analysis of the ita1 mutant (Image by CHENG Weimin)
Fig.2 Model of the LPA1-ITA1-BRXL4 module regulating the molecular mechanism of tiller angle in rice (Image by CHENG Weimin)
