Abstract
BACKGROUND: The cytochrome P450 superfamily comprises a large group of enzymes crucial for the biosynthesis and metabolism of diverse endogenous and exogenous secondary metabolites in plants. Chrysanthemum, an ornamental genus with considerable medicinal value, is one of the most economically important floricultural crops in the world. The characteristics and functions of CYP450 genes in Chrysanthemum species, however, remain largely unknown. RESULTS: In this study, we identified 371 CYP450 genes in the Chrysanthemum indicum genome, and categorized them into 8 clans and 44 families through phylogenetic analysis. Gene duplication analysis revealed 111 genes in 47 tandem duplicated clusters and 28 genes in 15 syntenic blocks, suggesting that extensive duplication events may account for the rapid expansion of CiCYP450 superfamily. Additionally, extensive variations in gene structure, motif composition, and cis-regulatory element likely enhance the functional diversity of CiCYP450 proteins. Volatile metabolomic analysis detected a total of 53 distinct volatile organic compounds across the leaves, stems, and roots of C. indicum, with 19 and 16 compounds being exclusive to leaves and stems, respectively. Transcriptomic analysis identified 248 expressed CiCYP450 genes, with 31, 40, and 88 specifically or preferentially expressed in leaves, stems, and roots, respectively. Further correlation analyses between gene expression levels and compound contents highlighted 36 candidate CiCYP450 genes potentially responsible for the biosynthesis of 47 volatile organic compounds. CONCLUSIONS: The genome-wide analyses of cytochrome P450 superfamily offers essential genomic resources for functional studies of CiCYP450 genes, and is significant for the molecular breeding of Chrysanthemum.