Dipteran Parasitoid-Silkworm Interaction: Application of Genomic and Proteomic Tools in Host-Parasitoid Communication

The dipteran endoparasitoid Exorista bombycis (Tachinidae) infest the silkworm Bombyx mori (Lepidoptera: Bombycidae). The female fly lays eggs on host larval cuticle. E. bombycis eggs have proteinase containing a gluey substance on ventral surface that aids to attach egg on larval surface as well as in partial digestion of the larval cuticle for easy invasion of the newly hatched parasitoid larvae into hemocoel. On invasion, host hemocytes in circulating hemolymph recognize the foreign body that induces the accumulation of exclusive proteins in hemocytes and other tissues. These proteins/conjugates are identified by SDS-PAGE analysis or by 2D electrophoresis. Few of the exclusive protein bands/spots are analyzed by mass spectrometry coupled with de novo peptide sequencing. On E. bombycis infestation, detoxification mechanisms are activated in host hemocytes. Detoxification enzyme level, reactive oxygen species (hydrogen peroxide; H2O2), and lipid peroxidation activity are increased after the infestation. The antioxidative enzymes, viz., oxidase, superoxide dismutase, thioredoxin peroxidase, catalase, glutathione-S-transferase (GST), and peroxidases, showed enhanced presence in hemolymph plasma, hemocytes, and fat body. The infestation deactivated host defense by downregulated expression of several defense and immune genes as revealed by genome wide gene expression using hemocyte microarray and substantiated by quantitative PCR. Moreover, microarray showed inhibition of several genes encoding interacting proteins revealed by protein-protein interaction network. The review emphasized on the communication between dipteran parasitoid E. bombycis and the host larvae of B. mori as well as the supporting data from hymenopteran-lepidopteran interaction.