Banana MaWRKY49 and MaWRKY111 cooperate with MabZIP21 to activate the transcription of MaACS1 and MaACO1 during fruit ripening

Ethylene is essential for the ripening of climacteric fruit such as banana, but the transcriptional modulation of ethylene formation in ripening banana is not well studied. In this work, two WRKY transcription factors MaWRKY49 and MaWRKY111 were identified from banana fruit. MaWRKY49 and MaWRKY111 were both nucleus-localized transcriptional activators, the transcription of which continued to increase following banana fruit ripening. MaWRKY49 and MaWRKY111 not only stimulated the transcription of themselves to constitute the feedback regulatory loop, but also promoted the transcription of ethylene biosynthesis genes MaACS1 and MaACO1 by directly targeting the W-box elements. Moreover, MaWRKY49 and MaWRKY111 interacted with each other to form the heterodimer, contributing to further enhancement of their target gene transcription. Importantly, both MaWRKY49 and MaWRKY111 interacted with another transcriptional activator MabZIP21, which synergistically strengthened the transcription of MaACS1 and MaACO1. Collectively, our findings suggest that MaWRKY49 and MaWRKY111 cooperate with MabZIP21 to positively regulate the ripening of banana by promoting transcription of ethylene biosynthesis genes MaACS1 and MaACO1.