Wheat WW Domain-Containing Protein TaCFL1 Negatively Regulates Cuticular Wax Biosynthesis.

Waxy cuticle covers plant aerial organs and protects plants against environmental challenges. Although improved cuticle-associated traits are aimed at the wheat breeding programs, the mechanism governing wheat cuticular wax biosynthesis remains to be elucidated. Herein, wheat WW domain-containing protein TaCFL1 is characterized as a negative regulator of wax biosynthesis. The knockdown of expression results in a 15% increase in wax accumulation and decreased leaf cuticle permeability in bread wheat. Furthermore, wheat class IV homeodomain transcription factors TaHDG1.1 and TaHDG1.2 are identified as partially redundant activators of wax biosynthesis. The silencing of or expression leads to an 11% reduction in epidermal wax accumulation and an increase in leaf cuticle permeability wax, while the co-silencing of and results in a 31% reduction in epidermal wax accumulation and a further increase in wax in the leaf cuticle permeability. Moreover, wheat 3-Ketoacyl-CoA synthase TaKCS10 is isolated as an essential component of the wax biosynthetic machinery. The silencing of expression results in a 22% reduction in wax accumulation and increased leaf cuticle permeability. In addition, we demonstrated that the expression is activated by TaHDG1.1 and TaHDG1.2, and that TaCFL1 attenuates the TaHDG1-mediated transcriptional activation of . This evidence supports that the WW domain-containing protein TaCFL1 negatively regulates wax biosynthesis via attenuating the transcriptional activation of the gene mediated by HD-ZIP IV transcription factor TaHDG1.