Three R2R3-MYB transcription factors from banana (Musa spp.) activate structural anthocyanin biosynthesis genes as part of an MBW complex

Bananas are among the most popular fruits in the world and provide food security and employment opportunities in several developing countries. An increased anthocyanin content could enhance the health promoting properties of banana fruits. The biosynthesis of anthocyanins is largely regulated at the transcriptional level. However, little is known about transcriptional activation of anthocyanin biosynthesis in banana. We analysed the regulatory activity of three MusaMYBs predicted by bioinformatic analysis to transcriptionally regulate anthocyanin biosynthesis in banana. MusaMYBA1, MusaMYBA2 and MusaMYBPA2 did not complement the anthocyanin deficiency phenotype of the A. thaliana pap1/pap2 mutant. However, co-transfection experiments in A. thaliana protoplasts showed that MusaMYBA1, MusaMYBA2 and MusaMYBPA2 function as components of a transcription factor complex with a bHLH and WD40 protein, called MBW complex, resulting in the activation of the anthocyanin synthase and dihydroflavonol 4-reductase promoters from A. thaliana. The activation potential of MusaMYBA1, MusaMYBA2 and MusaMYBPA2 increased when combined with the monocot bHLH ZmR instead of the dicot AtEGL3. This work paves the path towards decoding the MBW complex-mediated transcriptional activation of anthocyanin biosynthesis in banana. Moreover, it facilitates research towards an elevated anthocyanin content in banana and other monocot crops.