Proteomic analysis of the immune response of the silkworm infected by Escherichia coli and Bacillus bombyseptieus

Abstract The silkworm, Bombyx mori, is an economically important insect with a 5 000‐year history of domestication. During evolution, the silkworm has developed highly effective defenses against invasion and parasitization by microorganisms. In this study, two microorganisms Escherichia coli and Bacillus bombyseptieus were orally infected to silkworm larvae. After infection with E. coli and B. bombyseptieus for 24 h, we investigated the polypeptide changes in the hemolymph, midgut and integument using two‐dimensional gel electrophoresis and matrix‐assisted laser desorption ionization time of flight mass spectrometry. Forty‐seven differentially expressed proteins were identified in these tissues. They belonged to a variety of functional classes, including immune proteins, metabolic proteins and structural proteins. Compared with controls, E. coli‐infected silkworms showed 21 up‐regulated proteins, 25 down‐regulated proteins and lost one protein. After infection with B. bombyseptieus, silkworms showed 15 up‐regulated proteins, 27 down‐regulated proteins, lost three proteins and retained two proteins unchanged. We speculate that all these proteins may play a role in the silkworm immune response, although it is unclear why and how the two kinds of bacteria can so markedly alter expression of these proteins. These results offer valuable insights for measuring the proteomic responses of the silkworm innate immune mechanism.