Institute for Protein Research, Osaka University, 3–2 Yamada-oka, Suita, 565–0871, Japan.
Abstracts of the papers presented at the International Conference of Indian Virological Society on “Emerging and Re-emerging viral Diseases of the Tropics and Subtropics” at Indian Agricultural Research Institute, New Delhi, India, December 11–14, 2007.
Rice dwarf virus (RDV), a spherical double-shelled virus with a diameter of 70 nm, belongs to the genus Phytoreovirus in the family Reoviridae. Structural studies of three reoviruses, RDV (1), Bluetong virus (RDV) (2–5) and mammalian orthreovirus (6–8) have been extensively performed. We have proposed hierarchical structural organization of RDV by inspecting inter-subunit interaction of the double-shelled virus (1). The viral genome of RDVconsists of 12 segmented double stranded RNA (dsRNA) that encode seven structural proteins (P1, P2, P3, P5, P7, P8 and P9) and five non-structural proteins (Pns4, Pns6, Pns10, Pns11 and Pns12). P8 and P3 proteins are main components of the outer shell and the core, respectively. P2 and P9 proteins attach to the outer shell, while P1, P5 and P7 proteins are included in the core.
Omura's group have elucidated biological roles of non-structural protein in terms of structural organization of the virus (9–11). Among the non-structural proteins of RDV, Pns6, Pns11 and Pns12 are constituents of a viroplasm where the structural organization of the core is performed. In the process of the structural organization the core proteins P1, P3, P5 and P7 are concentrated in the interior region of the viroplasm, while the outer capsid proteins P2, P8 and P9 are accumulated in the peripheral region of the viroplasm. Prior to the structural organization of the core, P3 dimer and transcription complexes consisting of P1, P3, P5, P7 and a viral RNA are formed. The core structure is constructed in the interior of the viroplasm. The core moves toward the peripheral region of the viroplasm. After P8 trimers are attached to the surface of core, P2 and P9 bind to the core to form RDV particle.
