A novel MYB transcription factor from durian (Durio zibethinus), DzMYB1, regulates flavonoid biosynthesis in fruit pulp

Abstract

Flavonoids are phenolic substances and exhibit strong antioxidant properties. The biosynthesis of flavonoids is regulated by various transcription factors (TFs), with MYB TFs playing a key role in controlling essential genes within this pathway. In this study, we identified candidate MYB TFs from our pulp transcriptome database of durian ‘Monthong’ cultivar. MYBs exhibiting upregulation during the ripe stage were considered transcriptional activators, due to their positive correlation with flavonoid gene expression and flavonoid accumulation in ripe durian pulps. One candidate MYB activator, DzMYB1, which was highly expressed at the ripe stage, was selected for functional characterization. Studies involving transient expression of DzMYB1 in Solanum lycopersicum cv. Micro-Tom fruit demonstrated increased flavonoid content, as analyzed by LC–MS/MS, compared with the GFP control. Moreover, we showed that DzMYB1 controls flavonoid biosynthesis by interacting with the promoters of various flavonoid biosynthetic genes, including chalcone synthase, chalcone isomerase, and flavanone 3-hydroxylase, resulting in their transcriptional activation. Additionally, we found that DzMYB1 functions as a homodimer and binds to a homodimerized DzbHLH1 in the intricate regulation of flavonoid biosynthesis. These findings provide comprehensive insights into the functional roles of MYB protein in the regulation of the flavonoid pathway within durian pulps.