The SAGA histone acetyltransferase complex functions in concert with RNA processing machinery to regulate wheat wax biosynthesis

Wax mixtures comprising very long-chain fatty acids and their derivatives represent the major cuticular components and protect plant tissues from environmental stresses. Uncovering the regulatory mechanisms underlying wax biosynthesis is essential for the genetic improvement of the agronomically important crop bread wheat (Triticum aestivum L.). Herein, partially redundant ECERIFERUM 3 (TaCER3) proteins were characterized as essential components of wheat wax biosynthetic machinery. Furthermore, we demonstrated that the wheat Enoyl-CoA Reductase promoter-binding MYB transcription factor 1 (TaEPBM1)could directly target TaCER3 genes and recruit components of the SAGA histone acetyltransferase complex to mediate histone acetylation, thereby stimulating TaCER3 transcription and potentiating wax biosynthesis. Wheat RNA processing machineries, including the RNA exosome, SUPERKILLER (SKI) complex, cap-binding complex (CBC) components, TaSERRATE and its partners, as well as elongator subunits, affected the accumulation of TaCER3 transcripts and controlled wax biosynthesis. Silencing of wheat CBC components, TaSERRATE, and elongator subunits resulted in the accumulation of TaCER3 transcripts and increased wax biosynthesis. Importantly, the activation of wheat wax biosynthesis in the absence of RNA processing factors was suppressed by silencing TaCER3 expression. These findings suggest that the SAGA histone acetyltransferase complex functions in concert with the RNA processing machinery to regulate wheat wax biosynthesis, probably via affecting TaCER3 genes.