Genome-wide identification of the cytochrome P450 superfamily in Olea europaea helps elucidate the synthesis pathway of oleuropein to improve the quality of olive oil

Oleuropein, a secoiridoid derivative, is a major secondary metabolite in Olea europaea fruit that helps plants resist biological and abiotic stress and affects the quality of olive oil. Cytochrome P450 has been shown to be involved in the synthesis pathway of secoiridoid in other plants. However, no studies have analyzed the cytochrome P450 superfamily in olive at the whole-genome level. This study identified 335 olive P450 genes (OeCYPs) belonging to 10 clans and 50 families. Their structures, evolution, motif compositions, cis-acting elements, miRNA target sites, duplication events, Gene Ontology annotations, and expression patterns in different tissues were investigated. Comparison of the expression levels of OeCYPs and the metabolite contents revealed the functions of certain OeCYPs during fruit ripening. Homologous searching revealed some OeCYPs belonging to the CYP72 or CYP76 family that may regulate the biosynthesis of oleuropein. Based on this, we mapped the oleuropein synthesis pathway and predicted the functions of these OeCYPs in this pathway. This study provides a foundation for further verification of the functions of OeCYPs and can inform the cultivation of new varieties of O. europaea.