Soybean flower-specific R2R3-MYB transcription factor gene GmMYB108 induces anthocyanin production in Arabidopsis thaliana

R2R3-MYB transcription factors (TFs) are known to play a key role in regulating the expression of structural genes involved in plant flavonoid biosynthesis. However, the regulatory networks and related genes controlling isoflavonoid biosynthesis in soybean are poorly understood. We previously reported that ethephon application increases the production of isoflavonoids in soybean leaves. In this study, we attempted to identify a potential regulatory gene that positively controls isoflavonoid production in response to ethephon treatment in soybean (Glycine max L.). RNA sequencing (RNA-seq) revealed that ethephon application led to the upregulation of 22 genes, including the genes for R2R3-MYB TFs, related to isoflavonoid biosynthesis in soybean plants. Ethephon treatment highly induced the expression of GmMYB108, and its expression was exclusively enriched in flowers as determined using in silico and real-time quantitative PCR analyses. Furthermore, GmMYB108 overexpression resulted in an intense accumulation of anthocyanins as well as total flavonoid production in the leaf tissues of transgenic Arabidopsis plants. In addition, GmMYB108 overexpression increased the transcript levels of several genes involved in the biosynthesis of anthocyanins and their regulatory pathways in Arabidopsis. These results suggest that GmMYB108 is a potential positive regulator of the biosynthesis of flavonoids and anthocyanins in soybean flowers.