Horizontal gene transfer found at all levels of evolution (Introduction)

by David Turell , Thursday, July 14, 2022, 16:06 (653 days ago) @ David Turell

More research, more transfers found:

https://www.the-scientist.com/features/horizontal-gene-transfer-happens-more-often-than...

"Horizontal Gene Transfer Happens More Often Than Anyone Thought
DNA passed to and from all kinds of organisms, even across kingdoms, has helped shape the tree of life, to a large and undisputed degree in microbes and also unexpectedly in multicellular fungi, plants, and animals.

"...whatever the delivery vehicle, one thing is clear: in contrast to the simplicity of evolution from a common ancestor as commonly depicted, the branches of the tree of life appear to be inextricably tangled, and scientists are only just beginning to understand the extent of this complexity.

“'As our sampling increases, so does our power to detect horizontal gene transfers,” says Rokas. “So as we sequence more and more and more diverse lineages, I think we’re going to find more and more cases.”

***

"Still, when the first studies hinting at the possibility of HGT in eukaryotic organisms came out in the 2000s, researchers were hesitant to trust the results, citing numerous barriers that seemed insurmountable. For example, while foreign DNA can easily access bacterial genomes free-floating in the cytoplasm, in eukaryotes it would have to cross through highly regulated nuclear pores to enter the genome’s nuclear home. Also, because eukaryotic genomes are organized into pairs of homologous chromosomes that need to line up properly during meiosis, some researchers argued that large insertions would simply be too physically disruptive and would impede gamete production.

"To this day, the evidence for eukaryotic HGT is far sparser than that for bacterial HGT, and some scientists remain skeptical of its prevalence or importance in the evolution of diverse taxa. But Andrew Roger, a comparative genomicist at Dalhousie University in Nova Scotia, says that those who work with single-celled eukaryotes have readily embraced the idea. Genomic data—particularly long-read sequencing data, which establishes the genomic context for putatively foreign genes—has been unequivocal, he says. “The more genomes you get, the more you realize: here’s this chunk of chromosome from this organism in this one over here. And it’s just clearly a transfer.” In his mind, he adds, there’s little doubt that horizontal gene transfer has played a large role in the evolution of protists.

***

"Now, Rokas says, he thinks that DNA is not only moving around the tree of life, but it’s moving a lot more frequently than anyone had imagined, and the cases of HGT that have been identified are just a small sample of the total transfers that have taken place over evolutionary time. “My sense is there is orders of magnitude more integration than retention,” Rokas says. “So there is a lot more DNA coming into fungal genomes, and only a tiny fraction of that DNA is adaptive or selected enough to be maintained.”

***

“'We have the tools and the data now that allow us to quantify these transfers and quantify the impact they’ve had on evolution of eukaryotic genomes,” he adds. “I think the [whitefly] study that we did prompts us and prompts many others to start conducting such systematic analyses now. And we may come to realize that these transfers are not that not as rare as we thought they were.”

"Even if transfers in multicellular organisms are indeed less common than in microbes, Gilbert notes that evolutionary importance is not just a numbers game. “We want to think not [just] in terms of number, but also in terms of impacts. Perhaps just one transfer may have had a huge impact on the viability of some species.”

"Moran agrees. “In many cases, [horizontally transferred DNA] seems really central to the ecology or lifestyle of that particular group. Even if it’s only a tiny part of the genome, it can still be a major influence.'”

Comment: an enormous review article filled with research examples. I've pulled out the researcher's conclusions. HGT is a major evolutionary mechanism and as I view God's controls, a way He can step in for a 'dabble'.