Sec24C Participates in Cuticular Wax Transport by Facilitating Plasma Membrane Localization of ABCG5

Cuticular waxes synthesised in the endoplasmic reticulum of epidermal cells must be exported to the outer surface of the epidermis to fulfil their barrier function. Beyond transmembrane trafficking mediated by ABC transporters, little is known about the movement of wax molecules. In this study, we characterise a mutant named sugar-associated vitrified 1 (sav1), which exhibits a vitrified phenotype and displays a reduced root length when cultivated on sugar-free medium. The mutation in SAV1, which encodes the protein Sec. 24C, leads to ultrastructural alterations in cuticle membranes, decreased deposition of epicuticular wax crystals, and modifications in the chemical composition of very-long-chain fatty acids in cuticular waxes. SAV1 is a membrane protein and expressed during the early stages of seedling development. The defective phenotype of sav1-1 in sugar-free medium resembles that of abcg5, which encodes an ATP-BINDING CASSETTE TRANSPORTER subfamily G 5 (ABCG5) protein involved in cuticle layer formation. Further investigations reveal that SAV1 interacts with ABCG5, influencing the membrane localisation of ABCG5. Collectively, our results suggest that SAV1 plays a critical role in wax transport by altering the subcellular localisation of ABCG5.