Metabolic characterization of hemolymph in Bombyx mori varieties after Bombyx mori nucleopolyhedrovirus infection by GC-MS-based metabolite profiling.

The "Huakang 2" silkworm variety, bred by the Sericulture Research Institute of the Chinese Academy of Agricultural Sciences, is highly resistant to Bombyx mori nucleopolyhedrovirus (BmNPV) and effectively solves the issue of frequent Bombyx mori nuclear polyhedrosis in sericultural production. The molecular mechanism of its resistance to BmNPV, however, is still unknown. The purpose of the present study was therefore to identify these anti-BmNPV mechanisms by using metabolomics in combination with transcriptomics after subcutaneous injection of budded virus (BV) with high concentrations of BmNPV from specimens of the Baiyu N variety (which is highly resistant to BmNPV) and the Baiyu variety (which is sensitive to BmNPV). A total of 375 differential metabolites were identified, which mainly included sugars, acids, amines, alcohols, glycosides, and other small molecules. KEGG enrichment analysis and functional clustering of differential metabolites identified possible metabolic pathways, including tyrosine metabolism, oxidative phosphorylation, and alanine, aspartate, and glutamate metabolism. The differentially expressed genes (DEGs) identified by transcriptome analysis were annotated in KEGG. Association analysis showed that the metabolic pathways of different silkworm varieties are affected differently by BmNPV infection, triggering a series of complex physiological and biochemical changes in the organism. In particular, oxidative phosphorylation might be an essential pathway involved in regulation of disease resistance.