Variations of Hydrogen Peroxide and Catalase Gene Expression in Bombyx mori Diapause Eggs and HCl-treated Eggs During Cold Storage

The 48 h-old diapause eggs and the hydrochloric acid (HCl)-treated eggs of the silkworm,Bombyx mori, were chilled at 5 ℃ for over 30 d.It was found that hatchability of the diapause eggs increased markedly and that of the HCl-treated eggs decreased markedly.To clarify molecular mechanism underlying distinct effects of chilling on the hatch-ability of diapause eggs and the HCl-treated diapause eggs,hydrogen peroxide (H2O2) content,catalase mRNA transcriptional level and catalase activity in these two types of eggs were determined during chilling at 5 ℃.The results showed that,during chilling,as H2O2 content increased remarkably,mRNA transcriptional level of CAT gene was also up-regulated in both types of eggs.After chilling for 10～70 d,although H2O2 content,catalase mRNA transcriptional level and catalase activity all increased remarkably,H2O2 content in the diapause eggs was still significantly higher than that in the HCl-treated eggs,while catalase mRNA transcriptional level and catalase activity were lower than the HCl-treated eggs.That H2O2 content in HCl-treated eggs increased remarkably during chilling were likely to cause oxidation injury to the embryos and thus lead to the decrease of hatchability.Nevertheless,catalase mRNA transcriptional level and catalase activity in the diapause eggs during chilling were relatively lower and H2O2 content was relatively higher, but the embryos were not injured by oxidation,suggesting that chilling might have led to the induction of other anti-oxidation reactions in the diapause eggs.