The Preliminary Research Of Proteomics For The Process Of The Densvirus Infection Of The Silkworm

Bombyx mori densovirus (BmDNV) is one of the pathogenic viruses to the silkworm. The virus infects epithelial cells of midgut of silkworm and the pathogenic changes appear first in the cells at the anterior and posterior parts of midgut. Different silkworm varieties vary in susceptibility to the virus infection. When the susceptible varieties are infected by the virus, a series of tissue and cellular pathogenic changes develop as the disease advances. In order to understanding the molecular mechanism of densovirus infection to the silkworm, proteomic comparative studies were conducted to a susceptible silkworm variety on the midgut and haemolymph of both infected and healthy larvae by employing two-dimensional (2D) electrophoresis and matrix-assisted laser ionization time-of-flight mass spectrometry (MALDI-TOF MS) .The proteins separately extracted from the anterior, middle and posterior parts of midgut were comparatively analysed by 2D electrophoresis and MALDI-TOF MS. The results showed that there was less difference in the number, location and shape of the spots on the 2D image of proteins among the anterior, middle and posterior parts of midgut. Four distinguished specific spots which were found in the anterior and posterior parts of midgut might be lipoprotein precursor, vacuolar ATP synthase subunit B, alpha trypsin Chain A and actin respectively. One spot which was found in the middle part of midgut might be Kunitz trypsin inhibitor Chain A.As compared with the healthy larvae, some differentiated spots of proteins were identified in the midgut at different period post inoculation of BmDNV (Zhenjiang strain). In the early stage of infection, the cytochrome C reductase was expressed specifically. This enzyme is speculated functional in regulating and controlling apoptosis. In the middle stage of infection, chaperonin subunit zeta and cytochrome P450 were identified. They are also speculated to regulate and control apoptosis. In the late stage of infection, some important proteins such as trypsin, 30K lipoprotein and caspase-1 disappeared, which might be related to the lose of digestion function.Some differentiated spots of proteins were also identified in the haemolymph after inoculation of the virus. In the early stage of infection, some proteins such as phosphatase 2A inhibitor and peptidoglycan recognition protein were expressed responsively to the infection. In the middle stage of infection, some proteins such as cytochrome C oxidase were identified. While in the late stage of infection, a lot of proteins related to the regulation of cellular metabolism disappeared. These results implied that densovirus infection might also induce the expression and secretion of immunity-related proteins in the cells of fat body and heamolymph.As indicated above, the differentially expressed proteins in the midgut and haemolymph of the infected larvae, such as cytochrome C reductase, cytochrome C oxidase, cytochrome P450 and caspase-1, are speculated to be related to the regulation of the process of apoptosis. These implied the apoptosis may play an important role in the silkworm to defense the densovirus infection.