Objective  To study the difference of protein modification of silkworm(Bombyx mori) eggs during diapause induced by high or low temperature, and provide references for further exploration of molecular mechanism of insect diapause induction.

Method  The stable diapause silkworm strains induced by high or low temperature were screened out by raising the bivoltine silkworm varieties. Using the selected strains as materials, the eggs were incubated at 25 and 15 ℃ respectively. Samples were taken at the sensitive stage and the head pigmentation phase for epigenetic studies. The differences of protein modification were detected by SDS-PAGE electrophoresis and Western blot.

Result  The methylation level of protein in silkworm eggs in high temperature (25 ℃) group was always higher than that of low temperature (15 ℃) group, and there was significant difference at the head pigmentation phase. The levels of acetylation modification had always been significantly different between high and low temperature groups, and the high temperature group had significantly lower level compared with the low temperature group at the head pigmentation phase. The ubiquitination level of the low temperature group was always higher than that of the high temperature group, especially in the early stage of development. The levels of phosphorylation modification of both groups were high overall, and there was no significant difference between high and low temperature groups. The malonylation levels of protein in silkworm eggs did not change significantly between high and low temperature groups. The levels of succinylation modification of high and low temperature groups were always low, and there were obvious differential modification proteins in late developmental stage.

Conclusion  There are significant differences in the protein ubiquitination and acetylation modification level of silkworm eggs incubated at 25 ℃ compared with those at 15 ℃ throughout development, and the levels of methylation are significantly different at the head pigmentation phase, suggesting that methylation, ubiquitination and acetylation play important roles in early diapause induction process of silkworm.