The enigmatic giant virus is a recently discovered subclass of extremely large viruses infecting eukaryotic organisms. These viruses are characterized by the large size of their virions. They also contain many undescribed genes not found in other life forms encoding hundreds to thousands of proteins. Another important trademark of this virus is their visibility under a light microscope.
Currently, the representation of giant viruses is grossly underexplored, with an unknown number of previously unidentified genes and proteins possibly waiting to be discovered.
Undocumented viral genes
Now, a study from researchers led by Aix-Marseille University identifies a new giant virus whose genome is populated by genes never before documented in research. The team states the Yaravirus, named after Yara, a water-queen figure in Brazilian mythology, was recovered from Lake Pampulha, an artificial lake in the Brazilian city of Belo Horizonte. The opensource study is published in the journal bioRxiv.
Previous studies show these much larger viral forms possess more complex genomes, giving them the ability to synthesize proteins, and perform DNA repair, DNA replication, DNA transcription, and DNA translation.
Prior to their discovery, it was assumed viruses couldn’t perform these actions, carrying only a handful of genes to support their replication and the production of capsids. This means that the evolution and classification of these giant viruses due to their evolutionary history and undescribed genes are of extreme importance. The current study identifies a newly discovered giant virus, the Yaravirus, with no recognizable genes.
New virus discovered in Brazil
The current study identifies a new virus after collecting amoebae in an artificial lake in Brazil resulting in the discovery of unusually small amoebae. Results show Yaravirus presents 80 nm-sized particles and 90% of Yaravirus genes are unrecognized, constituting orphan genes, also known as ORFans. Data findings show only six genes found bore a distant resemblance to known viral genes, meaning it is unclear what Yaravirus might be closely related to.
The lab states following current genomic protocols for viral detection, Yaravirus would not be recognized as a viral agent. They go on to stress it is pure speculation what Yaravirus is for the moment and suggest it could be the first isolated case of an unknown genus of amoeba-infecting virus, or an ancient giant virus could have evolved into a reduced genomic form. They conclude the amount of unknown proteins composing the Yaravirus particles reflects the variability existing in the viral world.
The team surmises they have discovered a new giant virus with unrecognizable genes. For the future, the researchers state Yaravirus expands the knowledge in regards to viral diversity and challenges the current classification of DNA viruses.
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