MdMYS1 positively regulates cuticular wax formation by directly activating MdKCS7 in apple

Abstract

Epicuticular wax is a crucial component of the apple fruit cuticle that forms a protective barrier against non-stomatal water loss and pathogen invasion and contributes to fruit appearance, thereby affecting fruit quality and commercial value. Although the biochemical pathways of plant wax biosynthesis have been well characterized, the transcriptional regulation of cuticular wax synthesis in apple remains poorly understood. In this study, based on the transcriptome data of russeted and nonrusseted apple (Malus domestica) pericarps sampled at 120 days after full bloom, MYB-SHAQKYF (MYS) transcription factor, MdMYS1, that exhibited different expression between the two types, was identified as a candidate regulator of cuticular wax biosynthesis. MdMYS1 was localized to the nucleus. Transient overexpression and silencing of MdMYS1 in apple fruits, together with stable transgenic analyses in apple seedlings, demonstrated that MdMYS1 positively regulates wax accumulation. Heterologous overexpression of MdMYS1 in tomato further increased fruit wax accumulation, suggesting a conserved function in wax regulation. Yeast one-hybrid and dual-luciferase assays demonstrated that MdMYS1 directly binds to the promoter of β-ketoacyl-CoA synthase 7 (MdKCS7) and activates its transcription. These findings identify MdMYS1 as a positive regulator of cuticular wax biosynthesis and reveal a regulatory link between a MYS transcription factor and MdKCS7-mediated very-long-chain fatty acid elongation. This study provides new insights into the transcriptional regulation of cuticular wax biosynthesis in apple and offers potential candidate genes for the genetic improvement of fruit appearance and postharvest performance.