RcMYB84 and RcMYB123 synergistically mediate JA induced defense against Botrytis cinerea in Rosa chinensis. Rosa chinensis cultivar:Old Blush

The role and functional mechanism of jasmonate (JA) in woody flower rose plants are not clear. In the present study, exogenous application of methyl jasmonate (MeJA) increased the resistance to Botrytis cinerea in Rosa chinensis Old blush, while silence of Allene Oxide Synthase (AOS) gene in the core JA biosynthetic pathway, or CORONATINE INSENSITIVE 1 (COI1) which acts as the co-receptor for JA perception, both suppressed rose defenses to B. cinerea, indicating the essential role of JA in B. cinerea resistance of rose plants. Further transcriptome analyses proposed the balance of primary and secondary metabolism was a crucial step for immunity initiation in roses and identified a group of MYB gene family members as good candidates of JAZ-interacting transcription factors having pivotal roles in JA triggered immunity. Moreover, based on the lesion sizes the protection role of JA spraying against Botrytis infection was inhibited significantly both in the double mutant of Ri-RcMYB84 and Ri-RcMYB123 and the single mutant of Ri-RcMYB84 or Ri-RcMYB123, further confirmed the crucial roles of RcMYB84 and RcMYB123 in the JA-induced defense to B. cinerea. Additionally, the key repressor of JA signaling JAZ1 direct interacted with RcMYB84 and RcMYB123 to deplete their free pools, and meanwhile enabled the binding of JAZ1-RcMYB84 complex to the promoter of RcMYB123 via CAACTG motifs to block its transcription, therefore, not only the expression of RcMYB123 but also the proteins of RcMYB84 and RcMYB123 were de-repressed with JAZ1 degradation upon JA treatment, and in turn activated the protection responses of rose plants to cope with B. cinerea infection. Collectively, our results proposed RcMYB84 and RcMYB123 synergistically mediated JA induced defense against B. cinerea, and shed light on the molecular mechanism underlying JA-induced pathogen resistance in roses.