In
Arabidopsis, photoperiodic
flowering is controlled by the regulatory
hub gene CONSTANS (
CO), whereas floral organ senescence is regulated by the
jasmonates (JAs). Because these processes are chronologically ordered, it remains unknown whether there are common regulators of both processes. In this study, we discovered that CO protein accumulates in
Arabidopsis flowers after
floral induction, and 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. We found that CO has a ZIM (ZINC-FINGER
INFLORESCENCE MERISTEM) like domain that mediates its interaction with the JA response
repressor JAZ3 (jasmonate ZIM-domain 3). Their interaction inhibits the repressor activity of JAZ3, resulting in activation of downstream transcription factors involved in promoting flower senescence. Furthermore, we showed that CO, JAZ3, and the
E3 ubiquitin ligase COI1 (Coronatine Insensitive 1) 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 coordinated recruitment of photoperiodic and JA
signaling pathways could be an efficient way for plants to chronologically order floral processes and ensure the success of offspring production.