Abstract
Background: Grain size is a critical factor that affects yield in wheat (Triticum aestivum). CRINKLY4 (CR4) receptor-like kinase regulates epidermal cell differentiation and seed development in several plant species, yet its functional role in wheat remains to be clarified. Results: In this study, we identified the TaCR4 gene, which encodes the CRINKLY4 receptor-like kinase homolog in wheat. We created overexpressing (OE) wheat lines with increased TaCR4-A expression and found that the grain length, width, thickness, and weight of the OE lines increased. Cytological analysis revealed that the overexpression of TaCR4-A increased the length, width, and area of wheat grain outer pericarp cells. Conclusions: This study demonstrated that TaCR4 positively regulates wheat grain size by regulating the size of grain epidermal cells.