Profiling Heliothis virescens gut gene expression in response to Cry1Ac intoxication

We constructed an oligonucleotide microarray representing over 15,000 transcripts from Heliothis virescens larvae and used it to study gene expression upon feeding on diet containing Cry1Ac toxin from Bacillus thuringiensis. Developmentally synchronized 4th instar larvae were randomly assigned to experimental groups and starved for 6 hours. Larvae were then fed a commercial diet containing 1 µg/ml of Cry1Ac toxin and dissected after for 0, 0.5, 2, 6, or 24 hours. Total RNA isolated from larval gut tissue was used to produce dye-labeled complementary RNA (cRNA) for microarray hybridization. Expression levels of H. virescens gut-specific transcripts after Cry1Ac feeding were compared with those of control larvae. Genes that responded to Cry1Ac feeding by up- or down-regulation were identified and the expression profiles of these genes during the experiment time course established.