Sucrose Phosphate Synthase Defends Nicotiana benthamiana against Potato Virus Y Infection via 14-3-3 Protein Interaction

Plant viruses disrupt host metabolic pathways to facilitate infection. Sucrose metabolism may modulate viral resistance, yet the mechanism remains unclear. We used label-free proteomics to investigate sucrose phosphate synthase (SPS) activity in Nicotiana benthamiana during potato virus Y (PVY) infection. We identified 464 differentially expressed proteins enriched in SPS activity, amino acid metabolism, and carbohydrate biosynthesis. Functional analysis demonstrated that PVY infection significantly upregulated NbSPS3 expression and enhanced SPS activity and sucrose accumulation, which reduced viral accumulation. Silencing NbSPS3 compromised sucrose synthesis and increased PVY accumulation, confirming an antiviral defense role. NbSPS3 specifically interacted with the 14-3-3 protein NbGF14a, a positive regulator of PVY resistance. Silencing NbGF14a also enhanced susceptibility to PVY, suggesting a coordinated defense mechanism involving sucrose metabolism and 14-3-3 signaling. NbSPS3-mediated sucrose biosynthesis was revealed as a critical metabolic defense strategy against PVY, offering new insights into plant-virus interactions and potential targets for engineering crop resistance.