@Article{IPB-1080, 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.}, 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}, url = {http://www.nature.com/nchembio/journal/v5/n5/full/nchembio.161.html}, 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.} }