Immunity system complexity: thanks to Asgard Archaea (Introduction)

by David Turell , Sunday, September 08, 2024, 17:05 (76 days ago) @ David Turell

Perhaps from two billion years ago:

https://www.sciencealert.com/human-defenses-against-viruses-first-evolved-billions-of-y...

"Long before multicellular life evolved, our planet was home to a widespread group of ancestral microbes.

"The living descendants of these ancient microbes were only discovered in 2015 through traces of their DNA, deep in the ocean between Greenland and Norway. Five years later, the lurking lifeforms – a superphylum of archaea called Asgard – were successfully grown in the lab for the first time.

"At first glance, under the microscope, they looked a lot like bacteria. But archaea cells are evolutionarily closer to eukaryotic life forms, like plants and animals, than they are to their simpler microbial cousins.

"Based on their genomes, some scientists think Asgard archaea and our eukaryotic ancestors parted ways around 2 billion years ago, paving the way for all complex life on Earth, including animals, plants, fungi, protists, and most algae.

"Whatever that common ancestor looked like, at some point they had to incorporate a nucleus into their basic structure. Some scientists suspect Asgard ancestors developed one from a virus, which established a protective compartment referred to as a viral factory. Mitochondria, meanwhile, might have come from gobbling up a bacterial ancestor. (my bold)

***

"The team found that compared to bacteria, Asgard archaea have evolved a broad array of defense systems, some of which are also innate in eukaryotes.

"Of all the defense systems in the genomes from Asgard archaea analyzed, roughly 2 percent were linked to an immune protein, called viperin, which combats a wide array of viral infections by seemingly 'silencing' viral reproduction.

"Today, viperin plays a role in the immune systems of all complex life on Earth, which suggests it was present in the last common ancestor of archaea and eukaryotes.

"According to the new findings, eukaryotic viperins and Asgard viperins are "sister proteins and share a common ancestor".

"'It says that not only did eukaryotes get all these rich structural proteins that we've seen before in Asgards," explains integrative biologist Brett Baker from UT, "now it's saying that even some of the defense systems in eukaryotes came from Asgards."

"In addition to viperin, nearly 8 percent of the Asgard archaea defense genes analyzed were associated with argonautes. These are immune proteins that chop up DNA to halt the spread of a virus.

"In all domains of life on our planet, from archaea and bacteria to eukaryotes, argonautes act as "programmable immune systems"."

Comment: dhw asks why viruses were created. This article shows how viruses helped in developing eukaryote cells. ID theorists allow for some natural evolutionary processes at work along with active design work.