Vap27-1 Interacts with Kcs6 and Cer2 to Facilitate the Biosynthesis of Very- Long-Chain Fatty Acids

Abstract

Cuticular wax, primarily composed of very-long-chain fatty acids (VLCFAs) and their derivatives, forms a critical hydrophobic layer on plant surfaces, acting as a protective barrier against biotic and abiotic stresses. The biosynthesis of VLCFAs and their derivative wax occurs in the endoplasmic reticulum (ER) and is subsequently transported to the plant surface. While substantial research has focused on cuticular wax biosynthesis enzymes and their transcriptional regulation, the mechanisms by which these enzymes are modulated by proteins within cytosol organelles remain poorly understood. In this study, we identified that β-ketoacyl-CoA synthase 6 (KCS6), an ER-localized rate-limiting enzyme in VLCFAs biosynthesis, is enriched at ER-plasma membrane contact sites (EPCS). We further demonstrated that KCS6 and its cofactor ECERIFERUM 2 (CER2) interact with vesicle-associated membrane protein-associated protein 27-1 (VAP27-1), a key regulator of EPCS formation and stabilization. Overexpression of VAP27-1 in Arabidopsis thaliana resulted in a significant increase in total wax content, particularly in components with chain lengths longer than C28. Additionally, heterologous expressions of VAP27-1 in yeast enhanced the ability of KCS6-CER2 complex to produce VLCFAs. In conclusion, this study emphasized the critical role of VAP27-1 in regulating the biosynthesis of cuticular wax mediated by KCS6-CER2, providing new insights into the fine-tuning mechanisms of cuticular wax biosynthesis within the ER.

Keywords: Very-long-chain fatty acids, Endoplasmic reticulum, Cuticle wax, VAP27-1, KCS6, CER2, EPCS