Dwarf and Brittle Culm 3, encoding a glycosyltransferase, is required for mechanical strength in rice

Plant mechanical strength affects lodging resistance and stress tolerance, highlighting the importance of elucidating the regulatory mechanisms underlying cell wall development. In this study, we identified a novel dwarf and brittle culm mutant, dbc3, which exhibited reduced culm mechanical strength due to a thinner secondary cell wall, irregular distribution of the sclerenchyma cells under the epidermal layer and vascular bundle cells, as well as a significant reduction in cellulose and lignin content. Map-based cloning revealed that DBC3 encodes a xylan arabinosyltransferase belonging to the GT61 family. GUS staining and qRT-PCR showed that DBC3 was expressed in all tested tissues. Yeast one-hybrid, dual-luciferase assays and EMSA demonstrated that OsMYB63 directly bound to the DBC3 promoter to activate its expression. In the osmyb63 knockout mutant, DBC3 expression was significantly reduced, accompanied by a moderate decrease in stem mechanical strength. Taken together, these findings suggest that DBC3, as a direct target gene of OsMYB63, plays an important role in regulating plant mechanical strength by modulating cell wall development.