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

## TL;DR

This study shows that PSRP2/4 proteins in chloroplasts help a virus infect plants, and targeting these proteins could lead to sustainable antiviral strategies.

## Contribution

The study identifies PSRP2/4 as novel proviral factors in chloroplasts during TuMV infection.

## Key findings

- BcPSRP2/4 interacts with TuMV VPg and is localized to chloroplasts.
- Overexpression of BcPSRP2/4 increases viral cell-to-cell movement.
- Knockdown of BcPSRP2/4 reduces viral accumulation and disease symptoms without harming plant growth.

## Abstract

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.