Identification of MYB genes reveals their potential functions in cadmium stress response and the regulation of cannabinoid biosynthesis in hemp

Cadmium (Cd) is an inorganic heavy mutant pollutant in China. Industrial hemp (Cannabis sativa L.) is an important fiber crop used to remediate soils contaminated with heavy metals. Studies have shown that exogenous Cd stress can affect the production of secondary metabolites in industrial hemp plants. In the industrial hemp genome, we identified a total of 113 MYB genes, which are members of one of the largest and most important gene families that influences plant growth and secondary metabolite production. This study characterized 17 genes within the 1R-MYB subfamily, 88 genes in the 2R-MYB subfamily, and eight genes in the 3R-MYB subfamily. Synteny analysis indicated that there were three pairs of tandemly repeated CsMYBs, 21 pairs of segmental duplication, six CsMYBs were present before species differentiation, and 60 may be cannabis-specific CsMYBs. These results suggested that segmental duplication was the main factor during the evolutionary process that resulted in the expansion of the MYB family in hemp. Importantly, seven of these are key genes in response to Cd stress. Based on changes in gene expression and cannabinoid content under Cd stress, it was shown that CsMYB024 was affected by Cd stress and induced the cannabidiol biosynthesis pathway. Taken together, this study provides a comprehensive analysis of the cannabis MYB family and lays the foundation for the further study of biological functions of CsMYBs.