Brassinosteroid synthesis genes CcCPD/CcDWF4/CcDET2 in Carya cathayensis enhance resilience to salt stress through multi-faceted regulatory mechanisms

Hickory (Carya cathayensis), a valuable woody oil species with considerable economic importance, often suffers from reduced yields in its primary production regions due to soil salinization. Brassinosteroids (BRs), essential hormones that regulate plant growth, development, and stress responses, play a pivotal role in enhancing plant stress resistance. However, the functions and underlying mechanisms of key genes involved in BR biosynthesis in C. cathayensis under salt stress have yet to be fully elucidated. This study centered on the key BR biosynthetic genes CcCPD, CcDWF4, and CcDET2 in C. cathayensis, systematically examining their fundamental characteristics, including evolutionary conservation, protein properties, subcellular localization, and tissue expression patterns. Our findings also revealed that these genes exhibited dynamic expression patterns in response to salt, drought, and cold stresses, indicating their potential involvement in stress resistance through the modulation of BR biosynthesis. Functional validation through heterologous expression in Saccharomyces cerevisiae and overexpression in Arabidopsis thaliana further substantiated the roles of these genes in stress responses and unveiled their multifaceted regulatory mechanisms in salt tolerance. These mechanisms involve the maintenance of ion homeostasis, enhancement of antioxidant capacity and osmotic adjustment, as well as potential remodeling membrane integrity via fatty acid metabolism. This study provides preliminary insights into the mechanisms by which BR biosynthetic genes in C. cathayensis enhance salt tolerance, offering vital targets for the molecular breeding of salt-tolerant woody plants.