Genome-wide analysis of the cytochrome P450 superfamily suggests its roles in coumarin biosynthesis and salt stress response in Melilotus albus

Coumarin, a secondary metabolite from the plant phenylpropane pathway, was certified as an important natural product for plants in response to abiotic stresses. Cytochrome P450s represent the largest monooxygenase superfamily in kingdoms, participating in various biochemical processes including coumarin biosynthesis. Here, we reported a total of 290 P450 genes identified from the Melilotus albus genome, and these MaP450s were grouped into 9 clans. These genes were unevenly distributed in eight chromosomes and all of them contain highly conserved feature motifs of P450s. MaCYP82L1 was differentially expressed in JiMa46 and JiMa49, meanwhile up-regulated in response to NaCl treatment. The heterologous expression in yeast showed that the MaCYP82L1 transformed yeast cells exhibited obvious resistance under drought and salt stresses. Furthermore, overexpression of MaCYP82L1 increased coumarin content in transgenic hairy roots. This study not only identified MaCYP82L1 as an important regulator that adjusts drought and salt resistance, but also provided a link between coumarin metabolism and abiotic stresses.