Maize glossy6 is involved in cuticular wax deposition and drought tolerance

Cuticular waxes, long-chain hydrocarbon compounds, form the outermost layer of plant surfaces in most terrestrial plants. The presence of cuticular waxes protects plants from water loss and other environmental stresses. Cloning and characterization of genes involved in the regulation, biosynthesis, and extracellular transport of cuticular waxes onto the surface of epidermal cells have revealed the molecular basis of cuticular wax accumulation. However, intracellular trafficking of synthesized waxes to the plasma membrane for cellular secretion is poorly understood. Here, we characterized a maize glossy (gl6) mutant that exhibited decreased epicuticular wax load, increased cuticle permeability, and reduced seedling drought tolerance relative to wild-type. We combined an RNA-sequencing-based mapping approach (BSR-Seq) and chromosome walking to identify the gl6 candidate gene, which was confirmed via the analysis of multiple independent mutant alleles. The gl6 gene represents a novel maize glossy gene containing a conserved, but uncharacterized, DUF538 domain. This study suggests that the GL6 protein may be involved in the intracellular trafficking of cuticular waxes, opening the door to elucidating the poorly understood process by which cuticular wax is transported from its site of biosynthesis to the plasma membrane.