Genome-wide identification and expression profiling of the carotenoid cleavage dioxygenase (CCD) gene family in Brassica napus L

Carotenoid cleavage dioxygenase (CCD), a key enzyme in carotenoid metabolism, cleaves carotenoids to form apo-carotenoids, which play a major role in plant growth and stress responses. CCD genes had not previously been systematically characterized in Brassica napus (rapeseed), an important oil crop worldwide. In this study, we identified 30 BnCCD genes and classified them into nine subgroups based on a phylogenetic analysis. We identified the chromosomal locations, gene structures, and cis-promoter elements of each of these genes and performed a selection pressure analysis to identify residues under selection. Furthermore, we determined the subcellular localization, physicochemical properties, and conserved protein motifs of the encoded proteins. All the CCD proteins contained a retinal pigment epithelial membrane protein (RPE65) domain. qRT-PCR analysis of expression of 20 representative BnCCD genes in 16 tissues of the B. napus cultivar Zhong Shuang 11 ('ZS11') revealed that members of the BnCCD gene family possess a broad range of expression patterns. This work lays the foundation for functional studies of the BnCCD gene family.