Regulation of floral senescence in Arabidopsis by coordinated action of CONSTANS and jasmonate signaling

Abstract

In Arabidopsis, photoperiodic flowering is controlled by the hub gene CONSTANS (CO), while floral organ senescence is regulated by the jasmonates (JAs). As both processes are chronologically ordered, it remains unknown whether there are common regulators of both processes. In this study, we discovered that CO protein is accumulated in Arabidopsis flowers after the floral induction, whereas it displays a diurnal pattern in floral organs different from that in the leaves. We observed that altered CO expression could affect flower senescence and abscission by interfering with JA response, as shown by petal-specific transcriptomic analysis as well as CO overexpression in JA synthesis and signaling mutants. Interestingly, we found that CO has a ZIM-like domain that can mediate its interaction with the JA response repressor JAZ3 (jasmonate ZIM-domain 3). Their interaction could inhibit the repressor activity of JAZ3, resulting in the activation of downstream transcription factors involved in promoting flower senescence. Furthermore, we showed that CO, JAZ3 and the E3 ubiquitin ligase Coronatine Insensitive 1 (COI1) could form a protein complex in planta, which promotes the degradation of both CO and JAZ3 in the presence of JAs. Taken together, our results indicate that CO, a key regulator of photoperiodic flowering, is also involved in promoting flower senescence and abscission by augmenting JA signaling and response. We propose that the coordinated recruitment of photoperiodic and JA signaling pathways could be an efficient way for plants to chronologically order the floral process and ensure the success of offspring production.