COI1JAZ

COI1JAZ refers to the jasmonate signaling module in plants formed by the interaction of the F-box protein COI1 (CORONATINE INSENSITIVE1) with JAZ (JASMONATE ZIM-DOMAIN) proteins. COI1 is part of an SCF-type E3 ubiquitin ligase complex that partners with these repressors to regulate gene expression in response to jasmonates. The active jasmonate is JA-Ile, the conjugate of jasmonic acid with isoleucine, which serves as the endogenous ligand that enables COI1 to recognize and engage JAZ proteins.

In the presence of JA-Ile, COI1 binds JA-Ile and promotes the interaction with JAZ repressors. This interaction leads to ubiquitination of JAZ proteins by the SCFCOI1 complex and subsequent degradation by the 26S proteasome. As JAZ proteins repress transcription factors such as MYC2, their removal relieves repression and allows transcription of jasmonate-responsive genes involved in defense, stress responses, and development. Coronatine, a bacterial phytotoxin, can mimic JA-Ile and trigger the same pathway, highlighting the pathway’s ecological relevance.

JAZ proteins comprise a family characterized by a ZIM (TIFY) domain and a Jas (Jasmonate-associated) motif. The Jas motif acts as a degron in the JA-Ile–COI1–JAZ interaction, facilitating JAZ turnover. The COI1–JAZ module is conserved across many plant species, with multiple JAZ isoforms providing nuanced control over jasmonate responses. COI1 homologs and JAZ gene family expansion contribute to species- and tissue-specific signaling outcomes.

Biological significance of the COI1JAZ module includes defense against herbivores and pathogens, reproduction, and various developmental processes. The pathway integrates with other hormonal signals to coordinate growth and stress responses, representing a central node in plant adaptive signaling.