Research summary

The plant hormone jasmonates (JA) mediates plant defense responses against environmental stresses such as herbivore and pathogen attacks. 7-iso-(+)-jasmonoyl-L-isoleucine (JA-Ile), an active form of JA, induces protein-protein interaction (PPI) between COI1, the F-box protein in the SCF^COI1 ubiquitin E3 ligase complex, and the JAZ transcriptional repressor protein. This interaction causes JAZ degradation via proteasome, leading to plant defense responses, as well as growth inhibition or senescence. COI1 and 13 subtypes of JAZ are encoded in the genome of Arabidopsis thaliana, and JA-Ile can induce PPI between COI1 and most of JAZ subtypes to cause various physiological responses at the same time. However, the detailed function or ubiquitination sites/patterns of most of JAZ subtypes have not been elucidated so far, partially due to the genetic redundancy of JAZ genes. We developed comprehensive detection methods for PPI between COI1 and JAZ or JAZ and transcriptional factors (TFs). Based on these methods, we succeeded in the rational design of JAZ-subtype selective agonist that induces PPI between specific JAZ and COI1 (Nat. Commun. 2018). Furthermore, we have recently developed a JAZ-based stapled peptide as a selective inhibitor for JA-related TFs (RSC Chem. Biol. 2021). In this project, by using our original chemical tools, we would elucidate such complexed JA signaling pathway related to the regulation mechanism of the plant growth and defense responses, as well as the ubiquitination analyses of JAZ in planta