From ScienceDaily:
The new study examines the evolutionary dynamics of circular Rep-encoding single-stranded (CRESS) DNA viruses. The findings show that this broad class of single-stranded DNA viruses, which infect all three cellular domains of life, have acquired their genetic components through complex evolutionary processes not traceable to a single ancestral event. Rather, viruses are obsessive borrowers, appropriating genetic material from many sources, including bacterial, archaeal and eukaryotic cells as well as circular parasitic replicons, known as plasmids, and other mobile genetic elements, such as transposons.
When a group of mobile elements — like CRESS DNA viruses — arise from more than a single common evolutionary ancestor or ancestral group, they are known as polyphyletic. The phenomenon is common in the viral world, presenting both challenges and opportunities for researchers, as the definitions, taxonomies and evolutionary trajectories of this vast domain are reconsidered, with the help of powerful new techniques.
A better understanding of the promiscuous sharing of genetic information between different viruses and cell-derived genetic snippets may one day improve efforts to control these parasitic entities, some of which have had devastating effects on human wellbeing and crop yield.
Such explorations also hold the potential to shed new light on the origins of earth’s earliest life, and resolve the question of how cell-based life came to co-exist with the planet’s staggering array of viruses (dubbed the virome). Paper. (open access) – Darius Kazlauskas, Arvind Varsani, Eugene V. Koonin, Mart Krupovic. Multiple origins of prokaryotic and eukaryotic single-stranded DNA viruses from bacterial and archaeal plasmids. Nature Communications, 2019; 10 (1) DOI: 10.1038/s41467-019-11433-0 More.
Well, this is interesting, for sure: “The findings show that this broad class of single-stranded DNA viruses, which infect all three cellular domains of life, have acquired their genetic components through complex evolutionary processes not traceable to a single ancestral event.” Maybe there wasn’t a “single ancestral event” for cells either. Also: The hope is to “resolve the question of how cell-based life came to co-exist with the planet’s staggering array of viruses (dubbed the virome).” One commonly heard hypothesis is that viruses are degraded cells. It will be interesting to hear alternative theses.
See also: Before you go: One way viruses get spread “never should have evolved”
Reset! Different segs of virus genome can exist in different cells but work together
Viruses devolve. (PaV)
Virus expert highlights the conflict over whether viruses are alive In short, it is an open question. The question relates to the role viruses can play in evolution, among other things. Are they precursors of life, detritus of life, or something in between? Or all three? Keep the file open.
Viruses invent their own genes? Then what is left of Darwinism?
Why viruses are not considered to be alive
Another stab at whether viruses are alive
Phil Sci journal: Special section on understanding viruses
Should NASA look for viruses in space? Actually, it’s not clear that RNA came first. Nor is it clear that viruses precede life. A good case can doubtless be made for viruses being part of the scrap heap of existing life. But no matter. If you think you can find viruses in space, boldly go.
Why “evolution” is changing? Consider viruses
The Scientist asks, Should giant viruses be the fourth domain of life? Eukaryotes, prokaryotes, archaea… and viruses?
and
Are viruses nature’s perfect machine? Or alive?
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