A novel non-segmented double-stranded RNA virus from an Arctic isolate of Pythium polare

Area of Science:

• Mycology
• Virology
• Arctic biology

Background:

• Oomycetes, like Pythium polare, are significant in aquatic and terrestrial ecosystems.
• Virus discovery in oomycetes is less explored compared to other eukaryotic hosts.
• Arctic environments harbor unique microbial communities with potential for novel biological discoveries.

Purpose of the Study:

• To investigate virus infection in Arctic oomycete isolates.
• To characterize novel virus-like sequences found in Pythium polare.
• To determine the genomic and phylogenetic properties of a newly identified oomycete virus.

Main Methods:

• Screening of 39 Pythium polare isolates for virus-like double-stranded RNA (dsRNA).
• Next-generation sequencing (NGS) for identifying virus-like sequences.
• Full-length genome sequencing and bioinformatic analysis of identified viruses.
• Phylogenetic analysis based on deduced RNA-dependent RNA polymerase (RdRp) amino acid sequences.

Main Results:

• 14 out of 39 Pythium polare isolates contained virus-like dsRNA.
• Three distinct virus-like sequences were identified in isolate OPU1176 using NGS.
• The full genome of Pythium polare RNA virus 1 (PpRV1) was sequenced (5397 nt).
• PpRV1 possesses two overlapped ORFs, with ORF2 encoding an RdRp, and shows toti-like virus characteristics.
• Phylogenetic analysis places PpRV1 as closely related to unclassified arthropod toti-like viruses.
• PpRV1 infection in Pythium polare was observed to be symptomless.

Conclusions:

• A novel toti-like virus, PpRV1, has been identified and characterized in an Arctic oomycete.
• The discovery of PpRV1 expands the known host range for toti-like viruses.
• PpRV1 infects its oomycete host without causing apparent symptoms, highlighting potential for cryptic viral infections.