Gamma irradiation effects on the induction of three heat shock protein genes (piac25, hsc70 and hsp90) in the Indian meal moth, Plodia interpunctella

Effects of gamma irradiation on expression of heat shock protein genes and larval mortality were demonstrated in Plodia interpunctella, a serious pest of stored grains and food products. We obtained partial clones of three heat shock protein (hsp) genes (piac25, hsc70 and hsp90) and confirmed, by comparing deduced amino acid sequences, gene homology with corresponding hsps of other lepidopteran insects. Using Northern blot hybridization, expression levels of each gene were compared in fifth-instar larvae which were irradiated with gamma rays at doses from 0.1 to 2.0 kGy. The transcript level of hsc70 was increased at 0.5 kGy and higher doses, but the piac25 and hsp90 levels did not change. The hsc70 level also increased in irradiated pupae, but needed a 2.0 kGy dose. Mortality of irradiated larvae was also dose-dependent, and all larvae were killed by ≥1 kGy irradiation. Our results show that hsc70, but not piac25 and hsp90, was highly responsive to irradiation and suggest that specific hsp gene(s) may have a potential as molecular markers for the detection of irradiated insects.