New roles for cis-jasmone as an insect semiochemical and in plant defense

cis-Jasmone, or (Z)-jasmone, is well known as a component of plant volatile s, and its release can be induced by damage, for example during insect herb ivory. Using the olfactory system of the lettuce aphid to investigate volat iles from plants avoided by this insect, (Z)-jasmone was found to be electr ophysiologically active and also to be repellent in laboratory choice tests . In field studies, repellency from traps was demonstrated for the damson-h op aphid, and with cereal aphids numbers were reduced in plots of winter wh eat treated with (Z)-jasmone. In contrast, attractant activity was found in laboratory and wind tunnel tests for insects acting antagonistically to ap hids, namely the seven-spot ladybird and an aphid parasitoid. When applied in the vapor phase to intact bean plants, (Z)-jasmone induced the productio n of volatile compounds, including the monoterpene (E)-beta-ocimene, which affect plant defense, for example by stimulating the activity of parasitic insects. These plants were more attractive to the aphid parasitoid in the w ind tunnel when tested 48 h after exposure to (Z)-jasmone had ceased. This possible signaling role of (Z)-jasmone is qualitatively different from that of the biosynthetically related methyl jasmonate and gives a long-lasting effect after removal of the stimulus. Differential display was used to comp are mRNA populations in bean leaves exposed to the vapor of (Z)-jasmone and methyl jasmonate. One differentially displayed fragment was cloned and sho wn by Northern blotting to be up-regulated in leaf tissue by (Z)-jasmone. T his sequence was identified by homology as being derived from a gene encodi ng an a-tubulin isoform.