A banana transcriptional repressor MaAP2a participates in fruit starch degradation during postharvest ripening

Abstract

Fruit postharvest ripening is a crucial course for many fruits with significant conversion of biosubstance, which forms an intricate regulatory network. Ethylene facilitates the ripening process in banana with a remarkable change of fruit starch, but the mechanism adjusting the expression of starch degradation-related enzyme genes is incompletely discovered. Here, we describe a banana APETALA2 transcription factor (MaAP2a) identified as a transcriptional repressor with its powerful transcriptional inhibitory activity. The transcriptional level of MaAP2a gradually decreased with the transition of banana fruit ripening, suggesting a passive role of MaAP2a in banana fruit ripening. Moreover, MaAP2a is a classic nucleoprotein and encompasses transcriptional repressor domain (EAR, LxLxLx). More specifically, protein–DNA interaction assays found that MaAP2a repressed the expression of 15 starch degradation-related genes comprising MaGWD1, MaPWD1, MaSEX4, MaLSF1, MaBAM1-MaBAM3, MaAMY2B/2C/3A/3C, MaMEX1/2, and MapGlcT2-1/2-2 via binding to the GCC-box or AT-rich motif of their promoters. Overall, these results reveal an original MaAP2a-mediated negative regulatory network involved in banana postharvest starch breakdown, which advances our cognition on banana fruit ripening and offers additional reference values for banana varietal improvement.

Integrated Bioinformatics and Multi-Omics Analyses Reveal Possible Molecular Mechanisms for Seed Starch Content Differences between Glycine max and Cicer arietinum

“…Then, previous studies showed that Dof3 [77], MADS36 [78], bHLH6 [79], and bHLH-137 [80] have been experimentally demonstrated to regulate BMY expression to promote starch degradation. In our study, starch degradation-related genes BMY and PHS were found to have high expression levels in soybean (Table S1), and GmBMY was positively regulated by MYB, NAC, bZIP, Dof, bHLH, TCP, WRKY, ERF, and HD-ZIP.…”