This study investigates the differences in gene expression in Arabidopsis leaves in response to mechanical wounding and insect feeding by larvae of the cabbage butterfly (Pieris rapae). Using a cDNA microarray, researchers analyzed the expression of 150 genes in mechanically wounded leaves and identified genes that are specifically induced by insect feeding but not by wounding. They also found that water stress contributes to the regulation of a significant number of these genes. Comparing the results of mechanical wounding with insect feeding revealed distinct transcript profiles, with insect feeding inducing a unique gene (HEL) not induced by wounding. The study highlights the feeding strategy of P. rapae, which may minimize the activation of water stress-inducible defense genes. The results show that mechanical wounding and insect feeding trigger different gene expression patterns, with some genes being induced by both, while others are specifically activated by one or the other. The study also identifies COI1-dependent and COI1-independent wound-inducible genes, with COI1-dependent genes being regulated by jasmonate signaling. Water stress was found to influence the expression of many wound-inducible genes, and the study suggests that insect feeding may reduce the activation of water stress-related genes. The findings provide insights into the molecular mechanisms underlying plant responses to mechanical wounding and insect feeding, and the role of different signaling pathways in regulating gene expression in response to these stresses. The study also demonstrates the utility of cDNA microarrays in identifying gene expression patterns in response to various environmental stresses.This study investigates the differences in gene expression in Arabidopsis leaves in response to mechanical wounding and insect feeding by larvae of the cabbage butterfly (Pieris rapae). Using a cDNA microarray, researchers analyzed the expression of 150 genes in mechanically wounded leaves and identified genes that are specifically induced by insect feeding but not by wounding. They also found that water stress contributes to the regulation of a significant number of these genes. Comparing the results of mechanical wounding with insect feeding revealed distinct transcript profiles, with insect feeding inducing a unique gene (HEL) not induced by wounding. The study highlights the feeding strategy of P. rapae, which may minimize the activation of water stress-inducible defense genes. The results show that mechanical wounding and insect feeding trigger different gene expression patterns, with some genes being induced by both, while others are specifically activated by one or the other. The study also identifies COI1-dependent and COI1-independent wound-inducible genes, with COI1-dependent genes being regulated by jasmonate signaling. Water stress was found to influence the expression of many wound-inducible genes, and the study suggests that insect feeding may reduce the activation of water stress-related genes. The findings provide insights into the molecular mechanisms underlying plant responses to mechanical wounding and insect feeding, and the role of different signaling pathways in regulating gene expression in response to these stresses. The study also demonstrates the utility of cDNA microarrays in identifying gene expression patterns in response to various environmental stresses.