The Cytokinin Oxidase/Dehydrogenase TaCKX11-D Positively Regulates Grain Size in Wheat

Abstract

Grain size is one of the essential determinants of yield in wheat (Triticum aestivum L.). Cytokinin signaling affects grain size, and cytokinin oxidase/dehydrogenase (CKX) regulates cytokinin homeostasis by catalyzing cytokinin degradation. In this study, we identified that TaCKX11-D positively regulates wheat grain size. Overexpression of TaCKX11-D significantly increased grain length, grain width, grain thickness, and grain weight in Arabidopsis and wheat, whereas silencing TaCKX11-D in wheat decreased grain size and grain weight. Cytological analysis revealed that TaCKX11-D affects wheat grain size by regulating outer pericarp cell size. Overexpression of TaCKX11-D was determined to reduce endogenous cytokinin content in wheat. This demonstrates that TaCKX11-D promotes cell expansion and increases grain size by regulating cytokinin homeostasis. Moreover, we discovered that TaCKX11-D directly interacts with and is phosphorylated by TaMPK3 and TaMPK6. Our results reveal that TaCKX11-D positively regulates grain size and provide insights for wheat improvement breeding.

Keywords: TaCKX11-D; Triticum aestivum; Cytokinin oxidase/dehydrogenase; Grain size; Protein interaction; Transgenic plant.