@Article{IPB-10941, author = {Fonseca, S. and Chini, A. and Hamberg, M. and Adie, B. and Porzel, A. and Kramell, R. and Miersch, O. and Wasternack, C. and Solano, R. and}, title = {{(\+)-7-iso-Jasmonoyl-L-isoleucine is the endogenous bioactive jasmonate}}, year = {2009}, pages = {344-350}, journal = {Nat. Chem. Biol.}, doi = {10.1038/nchembio.161}, volume = {5}, abstract = {Hormone-triggered activation of the jasmonate signaling pathway in Arabidopsis thaliana requires SCFCOI1-mediated proteasome degradation of JAZ repressors. (−)-JA-L-Ile is the proposed bioactive hormone, and SCFCOI1 is its likely receptor. We found that the biological activity of (−)-JA-L-Ile is unexpectedly low compared to coronatine and the synthetic isomer (\+)-JA-L-Ile, which suggests that the stereochemical orientation of the cyclopentanone-ring side chains greatly affects receptor binding. Detailed GC-MS and HPLC analyses showed that the (−)-JA-L-Ile preparations currently used in ligand binding studies contain small amounts of the C7 epimer (\+)-7-iso-JA-L-Ile. Purification of each of these molecules demonstrated that pure (−)-JA-L-Ile is inactive and that the active hormone is (\+)-7-iso-JA-L-Ile, which is also structurally more similar to coronatine. In addition, we show that pH changes promote conversion of (\+)-7-iso-JA-L-Ile to the inactive (−)-JA-L-Ile form, thus providing a simple mechanism that can regulate hormone activity through epimerization.} }