An abscisic acid-responsive transcriptional regulatory module CsERF110-CsERF53 orchestrates citrus fruit coloration.

Carotenoid biosynthesis is closely associated with abscisic acid (ABA) during the ripening process of non-climacteric fruits, but the regulatory mechanism between ABA signaling and carotenoid metabolism remains largely unclear. Here, we identified two master regulators of ABA-mediated citrus fruit coloration, CsERF110 and CsERF53, which activated the expression of carotenoid metabolism genes (CsGGPPS, CsPSY, CsPDS, CsCRTISO, CsLCYB2, CsLCYE, CsHYD, CsZEP, and CsNCED2) to facilitate carotenoid accumulation. Further investigations showed that CsERF110 not only activated the expression of CsERF53 by binding to its promoter, but also interacted with CsERF53 to form a transcriptional regulatory module CsERF110-CsERF53. Furthermore, we discovered a positive feedback regulation loop between the ABA signal and carotenoid metabolism regulated by the transcriptional regulatory module CsERF110-CsERF53. Our results reveal that the transcriptional regulatory module CsERF110-CsERF53 responded to ABA signaling, thereby orchestrating citrus fruit coloration. Considering the importance of carotenoid content for citrus and many other carotenoid-rich crops, the revelation of molecular mechanisms underlying ABA-mediated carotenoid biosynthesis in plants will facilitate transgenic/gene editing approach development, further contributing to improving the quality of citrus and other carotenoid-rich crops.