Cuticular wax deficiency in glossy kale: molecular mechanisms and physiological consequences

Cuticular wax forms the outermost barrier on aerial plant surfaces, playing pivotal roles in water retention, defense against pathogens and pests, and adaptation to abiotic stresses. In kale (Brassica oleracea var. acephala), naturally occurring glossy mutants lacking epicuticular wax exhibit heightened sensitivity to drought, increased pathogen susceptibility, and reduced post-harvest shelf life. This review synthesizes recent advances in the molecular, biochemical, and physiological understanding of wax deficiency in glossy kale. We detail the biosynthetic pathways responsible for wax component production, including very-long-chain fatty acid (VLCFA) elongation, alkane and alcohol formation, and wax transport. The genetic and regulatory basis of glossiness is explored, highlighting mutations in core biosynthetic genes (CER1, CER3, KCS6, MAH1) and disruption of ABCG transporter-mediated export. Environmental and developmental regulation of wax production is examined, revealing complex interactions with drought, light, and organ identity. Finally, we evaluate breeding and biotechnological strategies for wax trait improvement, from marker-assisted selection to CRISPR-mediated gene editing. Understanding and manipulating cuticular wax biosynthesis in kale holds substantial promise for enhancing crop resilience, sustainability, and quality in a changing climate.