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NotSanguine [soylentnews.org] writes:

Phys.Org is reporting [phys.org] on a new genetic analysis [sciencemag.org] of viruses which shows that viral species are more similar to cellular species than previously shown.

From the article:

A new analysis supports the hypothesis that viruses are living entities that share a long evolutionary history with cells, researchers report. The study offers the first reliable method for tracing viral evolution back to a time when neither viruses nor cells existed in the forms recognized today, the researchers say.

The new findings [sciencemag.org] appear in the journal Science Advances.

The article goes on to discuss the method developed by researchers Arshan Nasir and Gustavo Caetano-Anollés from the Evolutionary Bioinformatics Laboratory, Department of Crop Sciences and Illinois Informatics Institute at the University of Illinois:

The new study focused on the vast repertoire of protein structures, called "folds," that are encoded in the genomes of all cells and viruses. Folds are the structural building blocks of proteins, giving them their complex, three-dimensional shapes. By comparing fold structures across different branches of the tree of life, researchers can reconstruct the evolutionary histories of the folds and of the organisms whose genomes code for them.

The researchers chose to analyze protein folds because the sequences that encode viral genomes are subject to rapid change; their high mutation rates can obscure deep evolutionary signals, Caetano-Anollés said. Protein folds are better markers of ancient events because their three-dimensional structures can be maintained even as the sequences that code for them begin to change.

By examining these structures [wikipedia.org]:

The researchers analyzed all of the known folds in 5,080 organisms representing every branch of the tree of life, including 3,460 viruses. Using advanced bioinformatics methods, they identified 442 protein folds that are shared between cells and viruses, and 66 that are unique to viruses.

"This tells you that you can build a tree of life, because you've found a multitude of features in viruses that have all the properties that cells have," Caetano-Anollés said. "Viruses also have unique components besides the components that are shared with cells."

In fact, the analysis revealed genetic sequences in viruses that are unlike anything seen in cells, Caetano-Anollés said. This contradicts one hypothesis that viruses captured all of their genetic material from cells. This and other findings also support the idea that viruses are "creators of novelty," he said.

Using the protein-fold data available in online databases, Nasir and Caetano-Anollés used computational methods to build trees of life that included viruses.

The data suggest "that viruses originated from multiple ancient cells ... and co-existed with the ancestors of modern cells," the researchers wrote. These ancient cells likely contained segmented RNA genomes, Caetano-Anollés said.

So now we have even more evolutionary "cousins". It may be time to get out that extra leaf for the dining table before Thanksgiving!

Original Submission