AUTHOR=Xiao Yunyi , Li Ying , Ouyang Lejun , Yin Aiguo , Xu Bo , Zhang Ling , Chen Jianye , Liu Jinfeng 

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

JOURNAL=Frontiers in Plant Science

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2022.1036719

DOI=10.3389/fpls.2022.1036719

ISSN=1664-462X

ABSTRACT=<p>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 <italic>MaGWD1</italic>, <italic>MaPWD1</italic>, <italic>MaSEX4</italic>, <italic>MaLSF1</italic>, <italic>MaBAM1-MaBAM3</italic>, <italic>MaAMY2B</italic>/<italic>2C/3A/3C</italic>, <italic>MaMEX1</italic>/<italic>2</italic>, and <italic>MapGlcT2-1/2-2 via</italic> 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.</p>