Barley stripe mosaic virus γb protein disrupts chloroplast antioxidant defenses to optimize viral replication

The plant antioxidant system plays important roles in response to diverse abiotic and biotic stresses. However, the effects of virus infection on host redox homeostasis and how antioxidant defense pathway is manipulated by viruses remain poorly understood. We previously demonstrated that the Barley stripe mosaic virus (BSMV) gamma b protein is recruited to the chloroplast by the viral alpha a replicase to enhance viral replication. Here, we show that BSMV infection induces chloroplast oxidative stress. The versatile gamma b protein interacts directly with NADPH-dependent thioredoxin reductase C (NTRC), a core component of chloroplast antioxidant systems. Overexpression of NbNTRC significantly impairs BSMV replication in Nicotiana benthamiana plants, whereas disruption of NbNTRC expression leads to increased viral accumulation and infection severity. To counter NTRC-mediated defenses, BSMV employs the gamma b protein to competitively interfere with NbNTRC binding to 2-Cys Prx. Altogether, this study indicates that beyond acting as a helicase enhancer, gamma b also subverts NTRC-mediated chloroplast antioxidant defenses to create an oxidative microenvironment conducive to viral replication.

Automated summary

The study reveals that BSMV infection induces chloroplast oxidative stress, and the gamma b protein interacts with NTRC to affect viral replication in plants. Overexpression of NbNTRC inhibits BSMV replication, while disruption of NbNTRC expression leads to increased viral accumulation and severity of infection.