A Single-Base Mutation in TaWAK3-B Reduces Plant Height via Cytoskeleton in Bread Wheat

Introduction of Reduced height (Rht) genes into modern wheat cultivars has resulted in 'Green Revolution' that skyrocketed wheat grain yields worldwide since the 1960s. These 'Green Revolution' cultivars show shorter plant height, but higher lodging resistance and harvest index. The identification and exploitation of novel Rht genes are of great significance for the development of high-yielding wheat cultivars. In this study, a semi-dwarf wheat mutant, d14078, with reduced plant height and grain size, was generated by ethyl methanesulfonate (EMS) mutagenesis. Here, through map-based cloning, we cloned the causal gene for the semi-dwarf phenotype of d14078 as TaWAK3-B that encodes a cell wall-associated receptor kinase 3. A single-base mutation occurred in the coding region of TaWAK3-B, resulting in an amino acid mutation from Glu to Lys (E938K) at residue 938, which reduces its stability and the formation of homodimers. The cytoskeletons were changed in both the d14078 and TaWAK3-B knockout mutants, as well as the TaWAK3-B overexpression of transgenic plants. Further investigation revealed that TaWAK3-B directly forms stable protein assembly with TaADF3-A (actin depolymerisation factor), TaKLCR1-A (kinesin light chain-related protein 1), and TaIQD2-D (IQ67-domain protein 2). These interactions and complex formations were significantly attenuated by the TaWAK3-B^E938K mutation. Therefore, our findings clarify TaWAK3-B regulating the microfilament and microtubule formation that elucidate on the regulation of wheat stem development.