Caffeic Acid -Methyltransferase Gene Family in Mango ( L.) with Transcriptional Analysis under Biotic and Abiotic Stresses and the Role of in Salt Tolerance.

Caffeic acid -methyltransferase () participates in various physiological activities in plants, such as positive responses to abiotic stresses and the signal transduction of phytohormones. In this study, 18 genes were identified in the chromosome-level reference genome of mango, named . A phylogenetic tree containing nine groups (I-IX) was constructed based on the amino acid sequences of the 71 COMT proteins from seven species. The phylogenetic tree indicated that the members of the MiCOMTs could be divided into four groups. Quantitative real-time PCR showed that all genes have particularly high expression levels during flowering. The expression levels of were different under abiotic and biotic stresses, including salt and stimulated drought stresses, ABA and SA treatment, as well as pv. and infection, respectively. Among them, the expression level of was significantly up-regulated at 6-72 h after salt and stimulated drought stresses. The results of gene function analysis via the transient overexpression of the gene in showed that the gene can promote the accumulation of ABA and MeJA, and improve the salt tolerance of mango. These results are beneficial to future researchers aiming to understand the biological functions and molecular mechanisms of genes.