Epigenetic Activation of Enoyl-CoA Reductase By An Acetyltransferase Complex Triggers Wheat Wax Biosynthesis.

The epidermal surface of bread wheat (Triticum aestivum) is coated with a hydrophobic cuticular wax layer that protects plant tissues against environmental stresses. However, the regulatory mechanism of cuticular wax biosynthesis remains to be uncovered in bread wheat. Here, we identified wheat Enoyl-CoA Reductase (TaECR) as a core component responsible for biosynthesis of wheat cuticular wax. Silencing ofTaECRin bread wheat resulted in a reduced cuticular wax load and attenuated conidia germination of the adapted fungal pathogen powdery mildew (Blumeria graminisf.sp.tritici). Furthermore, we established thatTaECRgenes are direct targets ofTaECRpromoter-binding MYB transcription factor1 (TaEPBM1), which could interact with the adapter protein Alteration/Deficiency in Activation2 (TaADA2) and recruit the histone acetyltransferase General Control Nonderepressible5 (TaGCN5) toTaECRpromoters. Most importantly, we demonstrated that the TaEPBM1-TaADA2-TaGCN5 ternary protein complex activatesTaECRtranscription by potentiating histone acetylation and enhancing RNA polymerase II enrichment atTaECRgenes, thereby contributing to the wheat cuticular wax biosynthesis. Finally, we identified very-long-chain aldehydes as the wax signals provided by the TaECR-TaEPBM1-TaADA2-TaGCN5 circuit for triggeringB.graminisf.sp.triticiconidia germination. These results demonstrate that specific transcription factors recruit the TaADA2-TaGCN5 histone acetyltransferase complex to epigenetically regulate biosynthesis of wheat cuticular wax, which is required for triggering germination of the adapted powdery mildew pathogen. A transcriptional activator recruits a histone acetyltransferase complex that epigenetically regulates the biosynthesis of wheat cuticular wax and is essential for triggering the germination of the powdery mildew pathogen.