Expression profiles of ten genes commonly up-regulated during plant defense against microbial pathogens were compared temporally during compatible and incompatible interactions with first-instar Hessian fly larvae, in two wheat lines carrying different resistance genes. Quantitative real-time PCR revealed that while a lipoxygenase gene (WCI-2 ) was strongly upregulated during the incompatible interactions, genes encoding b-1,3 endoglucanase (GNS ) and an integral membrane protein (WIR1 ) were moderately responsive. Genes for thionin-like protein (WCI-3 ), PR-17-like protein (WCI-5 ), MAP kinase (WCK-1 ), phenylalanine ammonia-lyase (PAL ), pathogenesis-related protein-1 (PR-1 ), receptor-like kinase (LRK10 ) and heat shock protein 70 (HSP70 ) were minimally responsive. The application of signaling molecules, salicylic acid (SA), methyl jasmonate (MJ) and abscisic acid (ABA), to insect-free plants demonstrated association of these genes with specific defense-response pathways. SA-induced up-regulation of a gene related to lipoxygenases that are involved in jasmonic acid (JA)-biosynthesis is suggestive of positive cross-talk between SA-and JA-mediated signaling pathways. Data suggest that alternative mechanisms may be involved since few of these classical defense-response genes are significantly upregulated during incompatible interactions between wheat and Hessian fly.