Carotenoid Cleavage Dioxygenases: Identification, Expression, and Evolutionary Analysis of This Gene Family in Tobacco.

Carotenoid cleavage dioxygenases (CCDs) selectively catalyze carotenoids, forming smaller apocarotenoids that are essential for the synthesis of apocarotenoid flavor, aroma volatiles, and phytohormone ABA/SLs, as well as responses to abiotic stresses. Here, 19, 11, and 10 genes were identified in , , and respectively. For this family, we systematically analyzed phylogeny, gene structure, conserved motifs, gene duplications, -elements, subcellular and chromosomal localization, miRNA-target sites, expression patterns with different treatments, and molecular evolution. genes were classified into two subfamilies and nine groups. Gene structures, motifs, and tertiary structures showed similarities within the same groups. Subcellular localization analysis predicted that family genes are cytoplasmic and plastid-localized, which was confirmed experimentally. Evolutionary analysis showed that purifying selection dominated the evolution of these genes. Meanwhile, seven positive sites were identified on the ancestor branch of the tobacco CCD subfamily. -regulatory elements of the promoters were mainly involved in light-responsiveness, hormone treatment, and physiological stress. Different family genes were predominantly expressed separately in roots, flowers, seeds, and leaves and exhibited divergent expression patterns with different hormones (ABA, MeJA, IAA, SA) and abiotic (drought, cold, heat) stresses. This study provides a comprehensive overview of the gene family and a foundation for future functional characterization of individual genes.