1Bio-oriented Technology Research Advancement Institution, Tokyo 105-0001, Japan.
2Laboratory of Ecological Information, Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan.
3Laboratory of Insect Physiology, Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan.
Plants infested by herbivores are known to emit specific blends of induced volatiles. Further, some of those induced volatiles influence the neighboring conspecific plants to be defensive against herbivores or pathogens. However, whether, and if so, how such specific blends of volatiles activate specific defense mechanisms in neighboring plants remained unanswered. Here we showed by RT-PCR analysis that volatiles emitted by Lima bean leaves infested by herbivorous mites (Tetranychus urticae) or beet armyworms (Spodoptera exigua), or by artificially damaged ones differentially activated asmonate-related defensive genes, basic basic pathogenesis-related (PR) proteins, lipoxygenase and phenylalanine ammonia-lyase, in neighboring uninfested lima bean leaves. This indicates the presence of different regulation mechanisms in jasmonate-related signaling pathway. Further, from inhibitory analysis, we found the possible involvement of the flux of Ca2+ to the cells, protein phosphorylation and dephosphrylation in the signaling pathway activated in the neighboring leaves. Direct defense against T. urticae and emission of volatile compounds that attract carnivorous natural enemies of T. urticae were also found in leaves neighboring to T. urticae-infested leaves. We conclude that neighboring plants may use volatiles emitted by herbivore-damaged plants to defend themselves directly and indirectly against the influx of herbivores by activating jasmonate-related signaling pathway.