Genome-wide identification and characterization of R2R3-MYB gene family and functional exploration on MYB34 in Isatis indigotica

MYB gene family plays crucial roles in growth and development, hormone signal transduction and metabolite regulation in plants. In this study, the identification and characterization of R2R3-MYBs and exploration on MYB34 were investigated in Isatis indigotica. The results revealed that there were 105 IiR2R3-MYB members, distributed across seven chromosomes. They were classified into 25 subfamilies, showing evolutionary and functional similarities to Arabidopsis thaliana. Moreover, 32 IiR2R3-MYBs involved in secondary metabolism pathways, whose expression patterns in different organs and stages were further studied using qRT-PCR. Furthermore, the functions of IiMYB34 were investigated. When IiMYB34 was introduced in Isatis indigotica, a notable decrease was observed both in the content of glucosinolates (GSLs) and the expression levels of IiCYP79F1 and IiCYP83A1 involved in aliphatic GSL biosynthesis, and IiCYP79B2, IiCYP83B1 and IiSOT16 involved in indolic GSL biosynthesis. Besides, over-expression of IiMYB34 in Nicotiana benthamiana resulted in an increased content of flavonoids and anthocyanins, and expression level of related enzyme genes. These findings contributed to the exploration on the regulatory mechanisms of MYBs involved in GSL biosynthesis and provided the potential molecular breeding strategies for Isatis indigotica.