Genome-Wide Analysis and Characterization of CYP450 Gene Family and Its Functional Analysis in Celery Seeds (Apium graveolens L.)

The Cytochrome P450 (CYP) superfamily plays an important role in the regulation of plant growth and development. However, the composition, evolutionary characteristics, and potential functions of CYPs in celery remain largely unexplored. Therefore, the objective of this study was to perform a genome-wide characterization of the Apium graveolens Cytochrome P450 (AgCYP) gene family and investigate its potential roles in seed development. In this study, a total of 227 AgCYPs were identified, and phylogenetic analysis classified them into six clades. Conserved motif and domain evaluations indicated that most AgCYP proteins possess conserved P450 domains. Chromosomal localization revealed an unequal distribution of AgCYPs across the 11 celery chromosomes. Duplicated AgCYP gene pairs were identified by synteny and Ka/Ks analyses, indicating that the duplicated AgCYPs have undergone strong purifying selection. Inter-genomic synteny analysis further reflects the closer relationship within Apiaceae. Analysis of cis-acting elements in the promoter regions identified an abundance of elements associated with light, hormone, and environmental stress. Moreover, AgCYPs showed stage-specific expression patterns and were correlated with monoterpene and phthalide accumulation during celery seed development, suggesting their potential functions in secondary metabolism in seed development. Treatment with exogenous auxin and its transport and biosynthesis inhibitors differentially induced distinct expression responses among AgCYPs, indicating their possible participation in auxin-related regulatory pathways. Moreover, candidate genes were selected. They exhibited diverse tissue-specific expression patterns and were potentially localized to the endoplasmic reticulum and interacted with some auxin-related proteins. In conclusion, this study provides the first comprehensive framework for understanding the functional diversification of AgCYPs in celery seeds, providing new insights into the evolutionary features and biological functions of the AgCYP gene family and establishing a foundation for future functional studies and molecular breeding applications.