Differential Profile Of Protein Expression In Embryonic Stage Of Bivoltine Silkworm(Bombyx Mori) Under Low And High Temperature Incubation

The diapause ability is an important behavior for insects to live through adverse environmental conditions. Understanding the mechanism of diapause may help lay the foundation for the development and utilization of economic insects and the prevention and treatment of agricultural pests. Silkworm, Bombyx mori, is one of the model insects for studying diapause. The diapause ability of bivoltine silkworm eggs is controlled by the environmental conditions in the embryonic stage of the maternal generation. Study on diapause associated proteins in the embryonic stage provides the experimental evidence for elucidation of the molecular mechanism of diapause.The silkworm eggs of Qiufeng, a bivoltine silkworm strain, were incubated under 25℃and 18℃separately, and soluble proteins and insoluble proteins were prepared from the eggs of five different embryonic stages including the labrum stage, shortening stage, end reversal stage, teachea colouring stage and head pigmentation stage, respectively. And proteins of newly-hatched silkworm were extracted with a different method. The differential profiles of protein expression in different embryonic stages from low and high temperature incubation were obtained with two-dimensional electrophoresis (2-DE) and image analysis system.There were no magnificent longitudinal changes detected during the first four embryonic stages. However, a large amount of structural genes expressing acidic proteins were activated during the head pigmentation stage. No distinctive protein spots were detected from the first four embryonic stages and newly-hatched silkworms; however, five and seven distinctive protein spots were detected from head pigmentation stage in soluble proteins and insoluble proteins, respectively. In which eight spots were identified by mass spectrometry to have credible best match proteins including egg specific protein, vitellogenin, putative cuticle protein, and pyruvate dehydrogenase kinase. Egg specific protein and vitellogenin are involved in embryonic development and differentiation. Pyruvate dehydrogenase kinase inhibits the oxidative decarboxylation of pyruvate. These different proteins may result in different material metabolism and energy metabolism. It was therefore presumed that low and high temperature incubation might induce different physiological and biochemical responses in silkworm eggs.