Giant, terrifying viruses invent their own genes

Pandoravirus quercus, seen through an electron microscope. The scale is equal to 100 nanometers. Credit: Copyright IGS-CNRS/AMU

Giant viruses able to think of genes and proteins that are found nowhere else on Earth, new research suggests.

As their name implies, giant viruses are large — as large as bacteria, and more than twice the size of typical viruses, scientists have previously reported. Giant viruses have a more complex than some simple micro-organisms, and many of their genes encode for proteins that are only in the giant viruses, according to previous studies.

These so-called orphan genes, scientists a mystery, but a new study may guess where they come from. Three new species of Pandoraviruses — a family of giant viruses described in 2013 — these genes originated in the viruses themselves. The giant viruses such as factories, churning out new genes and proteins — although the origin and purpose of this prolific gene the creation is still a mystery, the authors of the study wrote. [Small World: Gallery of Microscopic Beauty]

Even before the discovery of the giant viruses, viruses occupied a doubtful position on the tree of life: They contain many of the cellular material in the living organisms, including DNA or RNA, but they lack cell structure and cannot replicate outside of a host the two most important criteria for defining life.

At present, there are four well-known giant virus families: Mollivirus, Megavirus, Pithovirus and Pandoravirus. Researchers recently three new examples of Pandoravirus of samples that are taken in France, New Caledonia (French territory in the Pacific and Australia, and all of the new Pandoraviruses contained large amounts of orphan genes and proteins. But these be the genes differed among the viruses, which meant that it was unlikely that they originate from a common ancestor, the scientists reported.

“Ninety percent of their proteins share no significant similarity with proteins from other viruses, which are outside of their own family, or via the mobile network of microbes,” study co-author Jean-Michel Claverie, a professor of genomics and bioinformatics in the School of Medicine at Aix-Marseille University in France, said in a statement.

When the researchers analyzed and the fatherless, and the genes, which they compared with other parts of the viruses’ genomes. They are focused on regions of DNA sequences that are noncoding, and that are found between genes and they discovered similarities with the orphans. This hinted that each virus was the production of the new crop of genes from its own DNA, and that they did that randomly and spontaneously, according to the study.

Random mutations often occur in nature — spontaneous change of DNA plays a role in the evolution of new species. However, the new genes that the giant viruses generated produced proteins that are only found in the giant viruses — and nowhere else, the researchers reported.

The scientific findings suggest that new genes and proteins are generated regularly in Pandoraviruses — a concept that could be a game changer for how this giant virus family is examined. That, in turn, can shift the focus away from the evolutionary origin of the aberrant genes, Claverie said in the statement.

Moving forward, scientists would be trying to both unravel the molecular mechanisms that drive Pandoraviruses’ prolific gene discovery and the identification of the evolutionary forces that encouraged to “makers of genes,” Claverie added.

The findings are published online June 11 in the journal Nature Communications.

Original article on Live Science.


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