Comparative transcriptome analysis reveals a role for anthocyanin biosynthesis genes in the formation of purple peel in Minhou wild banana (Musa itinerans Cheesman)

To investigate the purple peel formation mechanism of the Minhou wild banana (Musa itinerans), epidermal cells of the purple and green parts of peel were subjected to RNA sequencing. In total, 3,640 differently expressed unigenes (DEGs) were identified. A KEGG enrichment analysis showed that these DEGs were mainly involved in flavonoid biosynthesis, phenylpropanoid biosynthesis, plant hormone signal transduction, starch and sucrose metabolism, and phenylalanine metabolism pathways, which suggested that the differential accumulation of secondary metabolites leads to the colour difference. Anthocyanin biosynthesis-related and transcription-factor genes with homologues that were crucial for anthocyanin biosynthesis in other plant species were identified as DEGs. We hypothesised that anthocyanin gene expression and subsequently anthocyanin metabolism contributed to the colour difference. The anthocyanin content in the purple peel was significantly higher than in the green peel, which verified the hypothesis. Quantitative real-time PCR on 11 DEGs was largely consistent with the RNA sequencing, indicating that the transcriptome data was reliable. Thus, the differential expression of anthocyanin biosynthesis-related genes correlates with the formation of the purple peel of Minhou wild banana. The generated comprehensive gene expression data provide insights into the molecular mechanisms underlying anthocyanin biosynthesis in banana peel.