Thursday, February 5, 2015
One of the memes of the movement against genetic engineering is that transgenic activity is somehow unnatural, but it turns out that interspecies gene transfer is not only natural, but can be critical to species survival.
(Image: Emerald elysia, Elysia chlorotica, an animal with plant genes that allow it to conduct photosynthesis. Credit: Sidney K. Pierce, used with permission.)
Examples include plant genes finding their way into animals, viruses into human DNA, bacteria into insects, hornworts into ferns and lots more.
Researchers recently have looked into the green sea slug, which is able to get energy from photosynthesis because takes up genetic material from algae and inserts them into its own. That allows the slug, known as the Emerald elysia, to conduct photosynthesis, like a plant does.
"There is no way on earth that genes from an alga should work inside an animal cell, and yet here, they do,” said study co-author Sidney K. Pierce of University of South Florida and University of Maryland, College Park. “They allow the animal to rely on sunshine for its nutrition. So if something happens to their food source, they have a way of not starving to death until they find more algae to eat."
The slug in this situation takes on a bright green color, from the plant chlorophyll in its genetic makeup.
The process of passing genetic material from one species to another without involving normal reproduction is sometimes called horizontal or lateral gene transfer. Researchers say this is fairly common among single-celled organisms, but is also found in higher forms of life, including plants, insects, and even humans.
The adzuki bean weevil has in its genome genetic material from the bacterium Wolbachia. And it turns out that Wolbachia have been able to insert their genetic material into any number of other species as well. One fruit fly species has the entire Wolbachia gene package in its own DNA.
And the authors of this paper report on gene transfers going the other way, from plants into bacteria and fungi. They report that it’s not accidental, and acts as a competitive advantage.
Writes co-author Nikolas Nikolaidis: “Our study reveals a rare phenomenon in molecular evolution where plant genes have been transferred to simple organisms like fungi and bacteria. The protein products of these genes are weakening the plant cell wall allowing plants to grow. In the case of bacteria and fungi, these proteins are related with the ability of these species to colonize plant roots and their virulence as plant pathogens. Our study suggests that by using proteins acquired from their hosts bacteria and fungi have found new adaptive ways to utilize their hosts resources and maybe become more advanced pathogens.”
Viruses are famous gene transfer agents. They swap genes among themselves through horizontal gene transfer, but also insert parts of their genetic code between and into unrelated species.
“Viruses also carry out natural "genetic engineering": a virus may incorporate some genetic material from its host as it is replicating, and transfer this genetic information to a new host, even to a host unrelated to the previous host,” says a report, Introduction to the Viruses, from the University of California at Berkeley.
It was long assumed that this couldn’t happen, but it turns out it happens a lot. The concept of mobile genetic elements, which move readily between even distant species, is discussed in last month’s issue of The Scientist.
The whole discussion throws traditional concepts of Darwinian evolution into question, which is discussed in this paper by Eugene V Koonin and Yuri I Wolf at the National Institutes of Health.
Even the human genome is full of material borrowed from unrelated species, which we now pass on genetically from one generation to the next. Our brains contain viruses that got into our genome millions of years ago, and now are fundamental parts of us. They change the way our brains work, and maybe they make us smarter.
‘Now it seems our own genome is a patchwork of raw genetic material coming from different places with different histories – that to me is very profound,” said Cedric Feschotte of the University of Utah in this article in the online journal Aeon.
“Standard theory says that mutations are supposed to happen within a species’s own genome, not come from somewhere else entirely. We now know that the appearance of new genes does not necessarily result from tweaks to native DNA, but might instead represent the arrival of far-flung visitors,” writes Ferris Jabr, the author of that report in Aeon.
© Jan TenBruggencate 2015