Insect feeding elicits the synthesis and emission of volatile compounds in the infested plants as part of the indirect defense against herbivory. By using an artificial caterpillar, MecWorm, it is possible to analyze the impact of mechanical wounding and chemical signals separately. Studies with lima bean revealed that long lasting continuous wounding of plant tissues is sufficient to induce volatile blends which are similar to those emitted after insect-feeding. Microarray techniques were used to investigate gene regulation processes on transcript levels in Arabidopsis thaliana
upon insect feeding and MecWorm treatment, respectively. On the whole genome background, significant changes in transcript levels have been found locally as well as systemically in both cases for about 5700 genes. Among these genes, 4100 were identically regulated, independently from the presence or absence of insect chemical components. In contrast, the observation of about 3200 regulated genes in systemically induced leaves indicates that insect signal compounds are involved in long distance responses.