Plant negative-strand RNA virus phosphoprotein condensates exploit host trafficking and lipid synthesis for viral factory assembly.

Abstract

RNA viruses often remodel host intracellular membranes to establish specialized replication compartments through viral protein-induced phase separation. However, the mechanisms underlying membrane remodeling and the characteristics that render these sites conducive to replication remain poorly understood, particularly in plant negative-strand RNA viruses. Here, we demonstrate that the phosphoprotein (P) of rice stripe mosaic virus (RSMV) forms biomolecular condensates via liquid-liquid phase separation (LLPS) to recruit essential components for viral replication factories (VFs). We identify a direct interaction between RSMV P and adenosine diphosphate (ADP) ribosylation factor 1 (OsARF1C), a crucial regulator of the coatomer protein I (COP I) vesicle transport pathway that is vital for viral replication. This interaction indirectly recruits OsARF1C's partner, phosphatidylinositol 4-kinase beta (OsPI4KB), which drives localized phosphatidylinositol-4 phosphate (PI4P) synthesis. Concurrently, the P protein modulates its aggregates and LLPS droplets through PI4P, thereby expanding the replication site and enhancing viral replication.