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Panicovirus accumulation is governed by two membrane-associated proteins with a newly identified conserved motif that

Jeffrey S Batten1, Massimo Turina, Karen-Beth G Scholthof

  • 1Department of Plant Pathology and Microbiology, Texas A&M University, College Station, TX, USA. battenj@gcs.k12.nc.us

Virology Journal
|March 10, 2006
PubMed

Insights

Panicum mosaic virus (PMV) replication relies on two proteins, p48 and p112, which act as viral RNA-dependent RNA polymerases. Key domains within these proteins are crucial for virus accumulation and systemic spread in plants.

Area of Science:

  • Virology
  • Molecular Biology
  • Plant Pathology

Background:

  • Panicum mosaic virus (PMV) possesses a positive-sense single-stranded RNA genome encoding two 5'-proximal proteins, p48 and p112.
  • The p112 open reading frame (ORF) contains a GDD-motif, characteristic of viral RNA-dependent RNA polymerases.

Purpose of the Study:

  • To investigate the roles of PMV p48 and p112 proteins in viral replication and pathogenesis.
  • To identify functional domains within the PMV replication proteins and assess their importance for virus accumulation and spread.

Main Methods:

  • Replication assays were performed in protoplasts to evaluate the sufficiency of p48 and p112 for PMV and SPMV replication.
  • Differential centrifugation and in vitro RNA polymerase activity assays were used to characterize the viral replication proteins.
  • Alanine scanning mutagenesis was employed to probe the function of a conserved domain (amino acids 306-405) in p48 and p112.

Main Results:

  • PMV p48 and p112 proteins were found to be sufficient for the replication of PMV and its satellite virus (SPMV).
  • These proteins are membrane-associated and exhibit RNA polymerase activity, supporting their role as viral replicase components.
  • Mutagenesis of the conserved domain revealed that specific amino acid substitutions, particularly in hydrophobic residues, severely impaired PMV accumulation and replication, suggesting a role in membrane localization and enzyme function.

Conclusions:

  • The p48 and p112 proteins of Panicum mosaic virus are essential viral replication proteins, functioning as the RNA-dependent RNA polymerase.
  • A conserved domain within these proteins is critical for viral RNA accumulation, with specific hydrophobic residues likely involved in membrane association and catalytic activity.
  • Mutations affecting this domain can impact systemic invasion and symptom development, highlighting the complex interplay between viral replication machinery and host responses.

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