Abstract
BACKGROUND: White spot syndrome virus (WSSV), one of the most devastating pathogens in global shrimp aquaculture, has been shown to hijack and reprogram host metabolic pathways to support its replication. Among the various host metabolic circuits, the malate-aspartate shuttle (MAS) is a key redox-balancing mechanism that facilitates the translocation of cytosolic NADH into mitochondria, thereby sustaining glycolysis and mitochondrial function. To date, however, the involvement of MAS in WSSV pathogenesis has not been documented. METHODS: In this study, we investigated the role of the MAS pathway in WSSV replication. We first assessed the mRNA level changes of MAS-related genes in WSSV infected shrimp. dsRNA-mediated gene silencing was also employed to examine its impact on the virus replication. To determine the direction of MAS during WSSV infection, we first silenced the MAS-related genes (e.g., GOT1 or GOT2), and subsequently replenished the corresponding metabolite to assess whether it could rescue the virus replication. RESULTS: At the viral genome replication stage of WSSV infection (12 hpi), significant upregulation of key MAS-related genes, including LvGOT1, LvGOT2, LvMDH1, LvAGC, and LvOGC, was observed in hemocytes of infected shrimp. Functional knockdown of these genes by in vivo dsRNA-mediated gene silencing significantly reduced WSSV gene expression and viral genome copy number, indicating that MAS activity is required for efficient WSSV replication. Furthermore, metabolite rescue experiments revealed a potential reversal of the MAS flux during the infection: supplementation with aspartate or α-ketoglutarate restored viral replication in LvGOT1-silenced shrimp, while oxaloacetate supplementation reversed the lowered replication caused by LvMDH1 silencing. CONCLUSION: This study demonstrates that WSSV activates the host MAS pathway to facilitate its replication and highlights the dynamic reprogramming of redox-associated mitochondrial metabolism in response to WSSV infection. The WSSV-induced reversed MAS might supply specific metabolites such as aspartate needed for virus replication or to prevent the TCA shut down.