The PSRP2/4 Proteins Promote Viral Infection by Interacting with the VPg Protein of TuMV

Chloroplasts, which are essential for plant defense and phytohormone signaling, contain ribosomal proteins that play key roles in viral infection processes. Plastid-specific ribosomal proteins (PSRPs), unique to chloroplasts, remain unexplored in their mechanistic roles during plant-virus interactions. In this study, we identified two PSRPs from non-heading Chinese cabbage (Brassica campestris ssp. chinensis) as interacting with turnip mosaic virus (TuMV, Potyvirus rapae). Subcellular localization revealed that BcPSRP2/4 is targeted to chloroplasts, while BiFC, Y2H, and LCAs confirmed their interaction with TuMV VPg (virus protein, genome-linked). Intriguingly, VPg altered the subcellular localization of BcPSRP2/4, suggesting an important role for BcPSRP2/4 in TuMV infection. Strikingly, overexpression of BcPSRP2/4 enhanced TuMV cell-to-cell movement, while psrp2 knockdown mutants in Arabidopsis exhibited a significant reduction in viral accumulation, highlighting their proviral roles. Furthermore, virus-induced gene silencing (VIGS)-mediated suppression of BcPSRP2/4 in non-heading Chinese cabbage resulted in milder symptoms upon TuMV infection without compromising plant growth: a distinct advantage over conventional resistance genes that incur fitness costs. These findings highlight PSRP2/4 as pivotal molecular hinges in chloroplast-virus interplay, offering novel targets for engineering sustainable antiviral strategies in cruciferous crops.