A positive-sense single-stranded RNA virus acquired a negative-sense open reading frame through recombination

Area of Science:

• Virology
• Molecular Biology
• Evolutionary Biology

Background:

• Single-stranded RNA (ssRNA) viruses are classified as either positive-sense or negative-sense based on their genome organization.
• Recombination or reassortment between these two major forms of ssRNA viruses has not been previously documented.
• Understanding viral genome evolution is crucial for predicting viral behavior and developing countermeasures.

Purpose of the Study:

• To report the discovery and characterization of a novel ssRNA virus, brine shrimp virga-like virus 1 (BSVV1).
• To investigate the evolutionary origins and genome structure of BSVV1, particularly its potential recombination between different ssRNA virus types.
• To determine the geographical distribution and replication capabilities of BSVV1.

Main Methods:

• Genome sequencing and analysis of BSVV1 to identify open reading frames (ORFs) and their homologs.
• Phylogenetic analysis to determine the evolutionary relationships of BSVV1's genetic components.
• Mass spectrometry to confirm the presence of predicted viral proteins.
• Geographical sampling of brine shrimp and viral culturing experiments.

Main Results:

• Discovery of BSVV1, a novel positive-sense ssRNA virus with a recombinant genome structure.
• BSVV1's genome contains ORFs with similarities to both positive-sense (RNA-dependent RNA polymerase) and negative-sense (glycoprotein) RNA viruses.
• BSVV1 is geographically widespread, found in brine shrimp across four continents, and can be cultured, proliferating to high titers.
• Mass spectrometry confirmed the expression of BSVV1's predicted proteins.

Conclusions:

• BSVV1 provides compelling evidence for ancient recombination events between viruses with differing genome organizations (positive-sense and negative-sense ssRNA).
• This discovery significantly expands our understanding of RNA virus evolution and genome plasticity.
• The widespread distribution and culturability of BSVV1 highlight its ecological relevance and potential for further study.