(+)-7-iso-Jasmonoyl-L-isoleucine is the endogenous bioactive jasmonate.
Hormone-triggered activation of the jasmonate signaling pathway in Arabidopsis thaliana requires SCF(COI1)-mediated proteasome degradation of JAZ repressors. (-)-JA-L-Ile is the proposed bioactive hormone, and SCF(COI1) 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.
Departamento de Genética Molecular de Plantas, Centro Nacional de Biotecnología-CSIC, Campus Universidad Autónoma, Madrid, Spain.
Sandra
S
Fonseca
Andrea
A
Chini
Mats
M
Hamberg
Bruce
B
Adie
Andrea
A
Porzel
Robert
R
Kramell
Otto
O
Miersch
Claus
C
Wasternack
Roberto
R
Solano
D017360:Arabidopsis / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D003517:Cyclopentanes / Q000378:metabolism*; D004951:Esterification; D007532:Isoleucine / Q000031:analogs & derivatives* / Q000378:metabolism; D015398:Signal Transduction; D020798:Two-Hybrid System Techniques
D003517:Cyclopentanes; C532883:jasmonoyl-isoleucine; D007532:Isoleucine