The RhHY5-RhMYB114a module coordinates anthocyanin biosynthesis and carotenoid degradation to drive light-responsive sequential color change in rose petal

Abstract

Sequential flower color change after anthesis is a distinctive trait with both adaptive significance and ornamental value; however, its molecular basis remains poorly understood. In ‘Mutabilis’ rose, petals undergo a light-dependent color transition involving coordinated remodeling of anthocyanin and carotenoid metabolism. Here, we reveal that the light signaling module RhHY5- RhMYB114a orchestrates both pigment pathways to drive this transition. We demonstrate that the MYB transcription factor RhMYB114a is strongly induced by light after anthesis and directly activates anthocyanin biosynthetic genes (RhANS, Rh3GT) and carotenoid cleavage dioxygenase genes (RhCCD4a, RhCCD7a), thereby simultaneously promoting anthocyanin synthesis and carotenoid degradation. RhHY5, a core light signaling component preferentially expressed after anthesis, binds specifically to a unique G-box3-G-box4 cis-regulatory module in the RhMYB114a promoter of the color-changing cultivar, driving high RhMYB114a expression and thereby “rebooting” anthocyanin biosynthesis. Promoter editing confirmed that the G-box3-G-box4 module confers stronger transcriptional activation of RhMYB114a promoter than a single G-box and suffices to reproduce the sequential color changing phenotype in tobacco, identifying it as the key genetic determinant. Furthermore, RhMYB114a directly binds its own promoter, forming a positive feedback loop that reinforces the regulatory circuit. Together, our study systematically elucidates the molecular mechanism by which the canonical light signaling pathway drives the reactivation of anthocyanin biosynthesis after flowering through cis-regulatory module in promoter. Furthermore, it provides novel strategies and potential targets for the generation of new plant cultivars via precise editing of key cis-regulatory elements.