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Viroplasm matrix protein Pns9 from rice gall dwarf virus forms an octameric cylindrical structure

Fusamichi Akita1, Naoyuki Miyazaki2,3, Hiroyuki Hibino1

  • 1National Agricultural Research Center, 3-1-1 Kan-nondai, Tsukuba, Ibaraki 305-8666, Japan.

The Journal of General Virology
|May 27, 2011
PubMed

Insights

The non-structural Pns9 protein is essential for rice gall dwarf virus (RGDV) viroplasm inclusion formation. This protein forms octameric structures, suggesting a conserved role in viral morphogenesis across reoviruses.

Area of Science:

  • Plant Virology
  • Structural Biology
  • Molecular Virology

Background:

  • Viroplasm inclusions are key structures in viral morphogenesis for many viruses in the Reoviridae family.
  • The non-structural Pns9 protein of rice gall dwarf virus (RGDV) is known to accumulate in these inclusions.

Purpose of the Study:

  • To determine the role of the Pns9 protein in the formation of RGDV-induced viroplasm inclusions.
  • To investigate the structural properties of the Pns9 protein.

Main Methods:

  • Immunofluorescence and immunoelectron microscopy were used on RGDV-infected cells.
  • Pns9 protein was expressed in Spodoptera frugiperda cells.
  • Conventional and cryo-electron microscopy were employed to analyze Pns9 structure.
  • Size-exclusion chromatography confirmed protein oligomerization.

Main Results:

  • Pns9 was identified as the minimal viral factor required for viroplasm inclusion formation during RGDV infection.
  • Pns9 was observed to form ring-like aggregates (approx. 100 Å diameter) in solution.
  • Cryo-electron microscopy revealed these aggregates as cylinders of octameric Pns9.
  • Octamerization of Pns9 was confirmed by size-exclusion chromatography.

Conclusions:

  • The Pns9 protein is the essential viral component for RGDV viroplasm inclusion assembly.
  • Pns9 self-assembles into octameric structures, forming cylindrical aggregates.
  • The octameric structure of Pns9 suggests a conserved role in morphogenesis, similar to rotavirus NSP2, in both plant and animal-infecting reoviruses.

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