Blue-light-enhanced interaction between ZmCRY1s and GL2 modulates epidermal wax composition in Zea mays

Cryptochromes (CRYs) are photolyase-like blue-light/ultraviolet-A (UV-A) receptors that regulate diverse aspects of plant growth and development. Maize (Zea mays), a major crop often grown under high UV-B radiation, harbors four copies of CRY. However, whether CRYs in maize have evolved to improve UV tolerance or acquire novel functions remains unclear. In this study, CRISPR-Cas9-engineered Zmcry mutants are used to investigate the functions of ZmCRYs in maize. The findings reveal that ZmCRYs act redundantly in mediating blue light signaling and inhibiting mesocotyl elongation. Furthermore, we demonstrate that ZmCRYs mediate blue light-enhanced UV-B stress tolerance in maize by upregulating the expression of genes involved in the biosynthesis of UV-B stress tolerance-related metabolites, including phenylpropanoids, flavonoids, and fatty acids. Further analyses show that blue light modulates both the accumulation and composition of epidermal waxes, suggesting that blue light enhances epidermal wax accumulation for UV-B stress tolerance. Notably, we identify that ZmCRY1 directly interacts with GLOSSY2 (GL2), a key acyltransferase in very-long-chain fatty acid metabolism, in a blue light-strengthened manner to mediate blue light-promoted C32 aldehyde accumulation, shedding new light on the enigma of the aldehyde-forming pathway in plants. These results highlight the critical roles of ZmCRY1s in mediating blue light-regulated epidermal wax biosynthesis and UV-B tolerance in Zea mays.