Methyl jasmonate is blowing in the wind, but can it act as a plant–plant airborne signal?

Interplant communication in nature is beginning to look like a reality with the field demonstration that tobacco plants downwind of damaged sagebrush suffer less herbivory, a response that appears to be mediated by an airborne signal. Sagebrush constitutively releases methyl jasmonate (MeJA), a compound that is highly active in inducing a number of physiological responses in plants. Damage increases the absolute quantity of the MeJA released as well as the proportion of MeJA in the isomeric cis form. Several studies have shown that volatile MeJA, when released in sufficient quantities, can simulate responses elicited by direct MeJA applications. Additionally, the thermodynamically unstable cis isomer, which is responsible for the characteristic jasmine odor, is thought to be the biologically active form of MeJA. To examine the hypothesis that the cis-MeJA release is responsible for the apparent inter-plant communication, we developed methods to: (1) entrain sagebrush constituents in water which preserved the isomeric shift in the MeJA released after damage; (2) chemically manipulate the MeJA trans : cis ratio; and (3) isolate nearly pure cis-MeJA by HPLC. These treatments were applied as aqueous sprays to a natural population of tobacco plants, however, an outbreak of specialist herbivores consumed all treated plants and chemical analysis on previously harvested treated leaf material was inconclusive. The hypothesis is currently being carefully investigated with laboratory experiments.