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

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 petalspecific
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.