Identification of the Cinnamyl Alcohol Dehydrogenase Gene Family in U-Triangle Species and Its Potential Roles in Response to Abiotic Stress and Regulation of Seed Coat Color in L.

Cinnamyl alcohol dehydrogenase (CAD) is essential for lignin precursor synthesis and responses to various abiotic stresses in plants. However, the functions of CAD in species, especially in , remain poorly characterized. In the present study, we identified a total of 90 genes across the U-triangle species, including , , , , , and . Comprehensive analyses of phylogenetic relationships, sequence identity, conserved motifs, gene structure, chromosomal distribution, collinearity, and acting elements were performed. Based on phylogenetic analysis, these genes were categorized into four groups, designated as groups I to IV. Most of the genes were implicated in mediating responses to abiotic stresses and phytohormones. Notably, members in group III, containing the bona fide genes, were directly involved in lignin synthesis. Furthermore, the expression profiles of genes exhibited differential responses to drought, osmotic, and ABA treatments. The expression levels of the , , , and genes were detected and found to be significantly lower in yellow-seeded compared to the black-seeded ones. This study provides a comprehensive characterization of genes in U-triangle species and partially validates their functions in , thereby contributing to a better understanding of their roles. The insights gained are expected to facilitate the breeding of yellow-seeded cultivars with enhanced stress tolerance and desirable agronomic traits.