Tuesday, April 21, 2015

“Naturally transgenic” sweet potato upends conventional wisdom

New research confirms that things are a lot wilder outside the genetic modification laboratory than in it.

We’ve known for a long time that genetic modification between distant species occurs in nature. It’s a process called horizontal gene transfer.

(Image: Naturally genetically modified sweet potato in a Hawaiian garden.)

Shucks, we’ve got virus DNA in our own genome. And RaisingIslands reported earlier about animals containing genes from plants. 

By comparison, this latest bit of information isn’t so strange: Bacterial DNA being found inside sweet potatoes. 

The new paper’s authors, led by Tina Kyndt of the Department of Molecular Biotechnology at Belgium’s Ghent University, call it “an example of a naturally transgenic food crop.”

What is notable, perhaps, is that the other examples revealed to date aren’t food crops, but sweet potatoes clearly are. What is also notable is that if you’re claiming that that there’s something inherently unnatural about moving genes between distantly related species, you don’t know nature.

In the case of the sweet potatoes, researchers found evidence of the genetic material of two different kinds of bacteria inside the sweet potato genome. Both are bacteria that are known to insert themselves into other species.

Agrobacterium rhizogenes and Agrobacterium tumefaciens are plant pathogenic bacteria capable of transferring DNA fragments ... bearing functional genes into the host plant genome,” the authors write.

That is, the genes not only get into the sweet potato, but they do things there. They remain functional. The authors suggest—but admit they can’t be sure yet—that something about the introduced genetic material is what made early humans select it for agriculture.

“It is … conceivable that one or more of the transferred genes contributed to the expression of a trait that was subsequently selected for during domestication,” they wrote. Kyndt and her co-authors assume that since none of the closely-related wild relatives of the sweet potato have the bacterial genes in them.

Sweet potatoes, Ipomoea batatas, are originally from South and Central America, but have been carried by early people around the world. The authors compared hundreds of samples of domesticated sweet potatoes from South and Central America, Oceania, Asia and Africa with wild varieties in South and Central America.

“The acquisition of new genes that confer a selective advantage is an important factor in genome evolution,” they wrote.

The  techniques used by the bacteria to insert their own genes into plants have been used by plant geneticists to do essentially the same thing, Kyndt and her co-authors say.

“This naturally occurring mechanism has been adapted by plant biotechnologists to develop genetically modified crops that today are grown on more than 10% of the world’s arable land, although their use can result in considerable controversy.”

© Jan TenBruggencate 2015

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