Wheat Class I TCP Transcription Factor TaTCP15 Positively Regulates Cutin and Cuticular Wax Biosynthesis

Cutin matrices and wax mixtures are major components of lipophilic cuticles, shielding plant tissues from stressful environments. Identifying the key regulators governing biosynthesis of cutin and cuticular wax in bread wheat (Triticum aestivum L.) could contribute to wheat breeding for stress resistance. In this study, we reported that the wheat class I TCP transcription factor TaTCP15 positively regulates cutin and cuticular wax biosynthesis. The CYP86A family cytochrome P450 enzymes, TaCYP86A2 and TaCYP86A4, were characterized as essential components of wheat cutin biosynthetic machinery. Wheat transcription factor TaSHN1 targets TaCYP86A2, TaCYP86A4, and wax biosynthesis gene TaECR and recruits the mediator subunit TaCDK8 to activate these genes' transcription. Furthermore, we demonstrated that TaSHN1 gene transcription is directly activated by the transcription factor TaTCP15. Expression of TaSHN1, TaCYP86A2, TaCYP86A4, and TaECR genes, as well as cutin and wax accumulation, was attenuated by silencing of the TaTCP15 gene. Collectively, these findings suggest that wheat class I TCP transcription factor TaTCP15 positively regulates cutin and cuticular wax biosynthesis, probably via directly targeting the TaSHN1 gene and upregulating TaCYP86A2, TaCYP86A4, and TaECR expression, providing valuable information for developing wheat plants with improved cuticle-associated traits.