Hypothesis on particle structure and assembly of rice dwarf phytoreovirus: interactions among multiple structural proteins

This study investigates protein-protein interactions in rice dwarf phytoreovirus (RDV), a plant virus with a 70 nm icosahedral structure containing 12 dsRNA segments. Researchers used the yeast two-hybrid system and far-Western blotting to map interactions among four major structural proteins: P1 (RNA polymerase), P3 (major core protein), P7 (nucleic acid-binding protein), and P8 (major outer capsid protein). Key findings showed that P3 binds to itself and to both P7 and P8, while P7 binds to P1, P3, and P8. Computer-aided analysis estimated protein copy numbers per virion as P1:P3:P7:P8 = 36:180:180:540. Based on these interactions and molecular ratios, the authors propose a structural assembly model where P3-P3 interactions form the core shell, and P7 functions as a central 'hinge' protein linking core and outer capsid components while also interacting with genomic RNA. The model suggests P1 polymerase associates with channels at the particle surface. These findings represent the first assembly model for plant reoviral particles based on experimentally observed protein-protein interactions.

Key findings

• P3 self-interacts to form the core shell, while P7 binds to three other structural proteins (P1, P3, P8), positioning it as a central assembly linker
• Protein stoichiometry determined as P1:P3:P7:P8 ratio of 36:180:180:540 copies per virion
• P7 functions as a 'hinge' protein integrating core and capsid layers while binding genomic dsRNA, facilitating both assembly and replication
• P1 polymerase interacts exclusively with P7 and likely localizes near the 32 channel sites at pentamer and hexamer centers