Recent discoveries show that jasmonate ZIM-domain (JAZ) transcriptional repressors are key regulators of jasmonate hormonal response. Jasmonate promotes interaction between JAZ proteins and the SCF(COI1) ubiquitin ligase, leading to JAZ degradation via the 26S proteasome in Arabidopsis thaliana. Elimination of JAZ repressors then frees the MYC2 transcription factor to stimulate jasmonate-dependent gene expression. Although jasmonic acid and methyl jasmonate were thought to be key regulators of jasmonate responses, they were ineffective in promoting SCF(COI1)-JAZ interaction and it is the isoleucine conjugate of jasmonic acid that acts in this signal transduction pathway. The discovery of JAZ transcriptional regulators greatly advances our understanding of how jasmonate signaling regulates plant growth and response to the environment.