The MYB transcription factor StMYBA1 from potato requires light to activate anthocyanin biosynthesis in transgenic tobacco

StMYBA1 from potato tuber was transformed into tobacco (Nicotiana tabacum) with the CaMV 35S promoter to investigate whether it can regulate anthocyanin biosynthesis in tobacco plants. As a result, anthocyanin accumulation was induced by overexpressing StMYBA1 in all tissues of transgenic tobacco lines. Several anthocyanin biosynthetic genes were highly expressed in leaves and roots of transgenic lines. In particular, the bHLH transcriptional partners NtAN1a and NtAN1b, especially NtAN1b, were up-regulated significantly in leaves and roots of StMYBA1-overexpressing tobacco. These results demonstrate that endogenous bHLH partners can be stimulated by overexpressing exogenous gene StMYBA1 in tobacco, and the elevated expression levels of bHLH partners are essential for anthocyanin production in plant tissues. Applying the dark conditions to the tobacco plants overexpressing StMYBA1 transiently, can down-regulate the expression levels of biosynthetic pathway genes and bHLH TFs, and subsequently reduce anthocyanin accumulation. We suggest that StMYBA1 can positively regulate anthocyanin biosynthesis in tobacco, and light is required for its function on anthocyanin accumulation.