Expression of stress-related genes in diapause of European corn borer (Ostrinia nubilalis Hbn.).

Abstract Diapause is a state of arrested development during which insects cope with many external and internal stressful factors. European corn borer, Ostrinia nubilalis , overwinters as a fifth instar freeze-tolerant diapausing larva. In order to explore diapause-linked stress tolerance processes, the expression of selected genes coding for stress-related proteins—glutathione S-transferase ( Gst ), thioredoxin ( Trx ), glutaredoxin ( Grx ), ferritin ( Fer ), metallothionein ( Mtn ), and heat shock proteins Hsp90 , Hsc70 , Hsp20.4 , and Hsp20.1 —was assessed in the fat body of diapause-destined, warm (22 °C) and cold (5 °C) acclimated diapausing larvae using the quantitative real-time PCR. Gene expression was normalised to mRNA transcripts for Actin and Rps03, and relative expression was calculated using non-diapausing larvae as a control group. During the initiation phase of diapause, the abundance of mRNA transcripts of Grx , Hsp90 , Hsc70 , and Hsp20.1 was significantly upregulated, Trx , Fer , Mtn , and Hsp20.1 were unchanged, while only Gst was clearly downregulated in comparison to non-diapause control. Later, in the early phase of diapause, the expression of most genes (except Trx and Hsp20.1 ) was upregulated in warm-acclimated larvae, while only Trx and Hsp90 were upregulated in cold-acclimated larvae. Furthermore, the relative expression of all genes (except Trx ) increased gradually throughout the diapause in cold-acclimated larvae. This result indicates that the half-life of mRNAs is prolonged during diapause at low temperature, which may lead to a gradual accumulation of mRNA transcripts. Our results show that both diapause programming and temperatures affect the expression of stress-related genes in Ostrinia nubilalis .