The MabZIP5–MaMYB69 module cooperates with MaERF55 to modulate banana fruit ripening via cell wall degradation

Abstract

The MYB protein family comprises numerous transcription factors with important functions in various biological processes in plants; however, their role in modulating banana fruit ripening has been rarely investigated. In this study, we identified an R2R3-type MYB gene, MaMYB69, which promotes fruit ripening by directly modulating cell wall degradation. The expression of MaMYB69, which encodes a nucleus-localized transcription activator, was induced by ethylene and upregulated during banana ripening. MaMYB69 activated the expression of MaPE, MaPL1, MaGAL, and MaPG3 by directly targeting their promoters. MaMYB69 overexpression in tomato and banana accelerated fruit ripening and stimulated cell wall-modifying gene expression. Moreover, MaMYB69 interacted with MaERF55 and strengthened its transactivation activity through downstream target genes. MabZIP5, an aroma biosynthesis regulator, acted directly upstream of MaMYB69, enhancing its transcription. MaMYB69 also formed a homodimer with itself and activated its expression. Collectively, our results show that MaMYB69 is pivotal in controlling banana ripening and softening and improve our understanding of the regulatory cascades involved in fruit ripening. MaMYB69 may serve as a potential target for improving fruit quality and extending the shelf life.