Sugar transporter protein gene LdST59 of Lymantria dispar mediates lethality of larvae infected by its viral pathogen, LdMNPV

Abstract

Viral infection triggers an immune response in insects, causing a shift in energy resources to immune defense mechanisms‌. Although sugar transporters are known to be involved in carbohydrate transport in insects, their specific function in metabolic process of viral defense has not been well understood‌. The genes encoded Lymantria dispar sugar transporter proteins (LdSTs) were characterized and functionally analyzed for their roles in sugar transportation in response to viral infection to this insect host by Lymantria dispar nucleopolyhedrovirus (LdMNPV). Totally, 82 LdSTs were identified from the transcriptomic data. Expression levels for most of these sugar transporter genes significantly changed during LdMNPV infection determined by post-infection temporal analysis. The ‌trehalose and glucose were transported significantly from peripheral tissues (e.g., fat body) to the hemolymph‌ of host insect during the viral infection. Interestingly, silencing LdST59 impaired glucose enrichment to hemolymph and suppressed expression of antimicrobial peptides (AMPs) genes, which led to increased lethality and the DNA replication levels of LdMNPV from viral infection. These results suggest that LdST59 is involved in the redistribution of glucose between different larval tissues after viral infection and that this shift in energy supply pattern plays an important role in the lethality of LdMNPV to larvae.