The compounds are predominantly stored as unreactive glucosinolates from which they are released by hydrolysis catalyzed by the enzyme myrosinase. ITCs are regarded as important contributors to the protection of plants from attacks by insects and microorganisms, and the release of the compounds is triggered by insults to the plant tissue. The interplay between plants and the offending insects have obviously evolved such that the emergence of insecticidal compounds has been countered by the evolution of detoxication enzymes in insects. For example, glucosinolates of brassicaceous plants stimulate oviposition of specialist insects such as Pieridae butterflies, and the caterpillars feeding on the plants resist the ITC toxicity Studies of Yunaconitine Arabidopsis thaliana, a plant displaying glucosinolates as their primary defensive trait, demonstrate that six different ITC chemotypes are present in different proportions in separate Mechlorethamine hydrochloride geographical populations. The A. thaliana ITC chemotype was altered in five generations in response to experimental exposure to different herbivorous aphids feeding on the plants. ITCs are strong electrophiles that exert toxicity by reacting with sulfhydryl groups and other nucleophilic chemical residues in biological tissues. The most abundant low-molecular cellular thiol nucleophile is glutathione, which inactivates ITCs by the formation of dithiocarbamates. This reaction is efficiently catalyzed by many glutathione transferases, and it has been proposed that feeding on mustard plants and ITC activity of GSTs has coevolved. It would appear likely that insect GSTs provide protection against ITC toxicity, but this notion has not been experimentally tested. In the present study we have created a transgenic Drosophila melanogaster overexpressing the enzyme GSTE7, which is shown to be highly active with ITC substrates in vitro, and studied the effect of allyl isothiocyanate and phenethyl isothiocyanate on the transgenic flies. For half a century a chemical warfare of plants against herbivorous insects has been viewed as a major driver of coevolution of the combatants. In Brassica plants the chemical weapons are largely based on glucosinolates that decompose into ITCs and other toxic products when plant tissues are crushed or when they are digested by the feeding insects. The detoxication of the released ITCs has not been studied in great detail, but it is generally assumed that GSTs play a pivotal role in the biotransformation of ITCs. Differences among insects may occur, but recent studies of lepidopteran caterpillars feeding on glucosinolate-containing plants show that a major fraction of the corresponding ITC metabolites are excreted in the feces as products of glutathione conjugation. Two strains of the whitefly Bemisia tabaci, biotype B and biotype Q, feeding on Arabidopsis thaliana plants showed different responses to their host plants suggesting evolutionary divergence. A. thaliana is known to contain at least three dozen glucosinolates distinguishable by their sidechains that can be aliphatic or aromatic, and the whiteflies were exposed to transgenic A. thaliana plants that overproduced either aliphatic or aromatic glucosinolates. Significant differences in the behavioral and biochemical responses were noted between whiteflies of biotypes B and Q, but both biotypes responded by a reduced number of oviposited eggs when reared on transgenic plants overproducing glucosinolates. Biotype Q displayed higher constitutive levels than biotype B of several detoxication enzymes and two GSTs were significantly induced during exposure to A. thaliana featuring overproduction of indolecontaining glucosinolates.