Involved in jasmonate (JA) signaling. Required for jasmonate signaling in plant defense responses. Can complement Arabidopsis coi1-1 mutant and restore jasmonate signaling. Required for JA-regulated defense responses to infestation by the leaffolder Cnaphalocrocis medinalis. May act on an initial response of jasmonate-regulated gene expression toward drought tolerance as part of a BHLH148-TIFY11D/JAZ12-COI1A complex (By similarity). Component of SCF(COI1) E3 ubiquitin ligase complexes, which may mediate the ubiquitination and subsequent proteasomal degradation of target proteins, including TIFY/JAZ family (By similarity). Interacts with TIFY6A/JAZ3, TIFY6B/JAZ4 and TIFY11D/JAZ12 in a coronatine-dependent manner. Interacts with TIFY9/JAZ5, TIFY10A/JAZ6, TIFY10B/JAZ7, TIFY11A/JAZ9 and TIFY11C/JAZ11 in a coronatine-dependent manner.