Abstract: When eggs of the bivoltine silkworm, Bombyx mori, are incubated at 25℃ under illumination and 15℃ under darkness, diapause and nondiapause eggs are laid, respectively. Our previous studies revealed that there was a significant difference in the level of hydrogen peroxide (H₂O₂) between the two incubation treatments in the bivoltine silkworm. Catalase is the key enzyme to scavenge H₂O₂ in insects. In this study the expression of catalase gene of the silkworm with two above incubation treatments was determined with RT-PCR to investigate the regulatory mechanism of H₂O₂ metabolism. The results indicated that compared to the 15℃ under darkness incubation, enhanced mRNA level and activity of catalase in the 25℃ under illumination incubation were observed at the induction and decision stage of diapause in maternal generation. In diapause eggs, catalase mRNA peaked at 24 h but disappeared at 72 h and thereafter while its activity increased until 96 h but kept at a low level and varied slightly 120 h after oviposition. In nondiapause eggs, however, both mRNA level and activity of catalase increased coinciding with embryogenesis. The results suggest that the induction of progeny diapause in the bivoltine B. mori by the 25℃ under illumination incubation may regulate the H₂O₂ level via affecting expression of catalase gene.

Key words: Bivoltine Bombyx mori, diapause, incubation, catalase, gene expression