Researchers find the genome of the cultivated sweet potato has bacterial DNA

April 21, 2015 by Bob Yirka report
Ipomoea batatas, Convolvulaceae, Sweet Potato, storage roots; Karlsruhe, Germany. Credit: Wikipedia

(Phys.org)—A team of researchers with members from Belgium, China, Peru and the U.S. has found evidence of bacterial DNA in the genome of the cultivated sweet potato. In their paper published in Proceedings of the National Academy of Sciences, the team describes their findings as an example of a naturally occurring transgenic food crop.

In modern times, scientists have created what are known as (GMOs), where plants or animals are modified to suit the particular needs of people in a certain region—to allow corn to grow in a dry climate for example. One common method of creating GMOs is to use bacteria that have been found able to modify the genes of a host as a carrier agent. GMOs have been met with suspicion in many parts of the world with some places banning them outright. Now, in this new effort, the researchers have found an example of a natural GMO that people have been eating for thousands of years: the .

Sweet potatoes have been growing wild in South America for thousands of years—over time, they were cultivated by people, and have since become a popular food in many parts of the world. But now it appears that a type of bacteria similar to the kind used by modern scientists to create many GMOs found its way naturally to cultivated sweet potatoes many generations ago and modified its DNA. To make this discovery, the researchers collected 291 sweet potato samples from cultivated sources across the globe along with nine wild sources and subjected them all to DNA analysis—they found that all of the cultivated potatoes carried at least two stretches of Agrobacterium DNA, while the wild species carried one. Their findings suggest the transfer of DNA to the potatoes occurred a long time ago, before they were carried to and grown in other parts of the world.

Sweet potatoes

The researchers suggest their findings could have an impact on the perception of GMOs by some who oppose their creation on the grounds that it is not safe. They claim that humans eating food that was genetically modified naturally, over thousands of years, proves that such foods are not harmful.

Explore further: Sweet potato DNA indicates early Polynesians traveled to South America

More information: The genome of cultivated sweet potato contains Agrobacterium T-DNAs with expressed genes: An example of a naturally transgenic food crop, Tina Kyndt, PNAS, DOI: 10.1073/pnas.1419685112

Abstract
Agrobacterium rhizogenes and Agrobacterium tumefaciens are plant pathogenic bacteria capable of transferring DNA fragments [transfer DNA (T-DNA)] bearing functional genes into the host plant genome. 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. While assembling small interfering RNAs, or siRNAs, of sweet potato plants for metagenomic analysis, sequences homologous to T-DNA sequences from Agrobacterium spp. were discovered. Simple and quantitative PCR, Southern blotting, genome walking, and bacterial artificial chromosome library screening and sequencing unambiguously demonstrated that two different T-DNA regions (IbT-DNA1 and IbT-DNA2) are present in the cultivated sweet potato (Ipomoea batatas [L.] Lam.) genome and that these foreign genes are expressed at detectable levels in different tissues of the sweet potato plant. IbT-DNA1 was found to contain four open reading frames (ORFs) homologous to the tryptophan-2-monooxygenase (iaaM), indole-3-acetamide hydrolase (iaaH), C-protein (C-prot), and agrocinopine synthase (Acs) genes of Agrobacterium spp. IbT-DNA1 was detected in all 291 cultigens examined, but not in close wild relatives. IbT-DNA2 contained at least five ORFs with significant homology to the ORF14, ORF17n, rooting locus (Rol)B/RolC, ORF13, and ORF18/ORF17n genes of A. rhizogenes. IbT-DNA2 was detected in 45 of 217 genotypes that included both cultivated and wild species. Our finding, that sweet potato is naturally transgenic while being a widely and traditionally consumed food crop, could affect the current consumer distrust of the safety of transgenic food crops.

Press release

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8 comments

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Cave_Man
5 / 5 (2) Apr 21, 2015
Agrobacterium adds dormant genes to sweetpotato=active coding sequences added that change dynamics of plant growth..........................I think not!
"They claim that humans eating food that was genetically modified naturally, over thousands of years, proves that such [GMO] foods are not harmful."


We humans can be infected by microbes that add their own DNA to ours. That doesn't mean we should go modifying our growth genes, same goes for our food. Seems fairly obvious to me....
gmugliston
4 / 5 (4) Apr 21, 2015
I am quite O.K. with naturally occurring bacterial DNA components in my natural food stuffs. What I am not O.K. with is having Del or Monsanto determine what bacterial DNA will be added. I find over all Monsanto especially is doing very bad genetic experiments with plants that are having a very, very negative effect on humans in terms of being able to actually farm without the next year's crop committing suicide...and then the farmers do. Why is that information from India not be public knowledge in the USA?

It is too soon to know if what is being genetically modified now is not deleterious and besides all experimental GMO crops are hidden from us legally...that in itself, does not bode well to increase my belief that those companies doing that genetic modification are benign.
gstark
5 / 5 (8) Apr 21, 2015
GMO is not evil... but not all GMO is not good either.

Using GMO tech to facilitate pesticide or herbicide use in not only morally wrong, it is self defeating in the long run.

Using GMO instead of lengthy cross-breeding to develop drought tolerance or the like is good.

One has to judge by the specifics. not the slogans.
Bongstar420
1 / 5 (2) Apr 21, 2015
Ya..its just one big cock blocking parade.
As long as someone doesn't get to decide, or someone doesn't get to force others to compensate them duly for their contribution, "I'm cool with it."

I'm sure you'd be cool with it if it was your product your way.

Why don't you invent better food and give it away for free?

I am quite O.K. with naturally occurring bacterial DNA components in my natural food stuffs. What I am not O.K. with is having Del or Monsanto determine what bacterial DNA will be added. I find over all Monsanto especially is doing very bad genetic experiments with plants that are having a very, very negative effect on humans in terms of being able to actually farm without the next year's crop committing suicide...and then the farmers do. Why is that information from India not be public knowledge in the USA?[q[
gstark
5 / 5 (4) Apr 21, 2015
Bongstar420, I don't understand your comment.

Monsanto has certainly developed seed lines using Genetic Use Restriction Technology (GURT).

These so-called Terminator seeds are a terrible idea.

Monsanto is also involved with adding immunity to Round-UP and internal expression of systemic pesticides to various seed lines...

Are you suggesting it is a selfish act to protest these actions?

You sound like you smoked your lunch.
WirelessPhil
not rated yet Apr 21, 2015
Look at that photo.
You show both sweet potatoes and yams.
They are two different potatoes.

When it comes to GMO food, the companies that make it should eat it until they grow old (iif they are lucky) and die. Then we can cut those people up and run test on them!
viko_mx
1 / 5 (3) Apr 22, 2015
The suggestion is that if it is found in the sweet potatoes DNA of bacteria in nature,then there is nothing unnatural and people to use bacteria for genetic modification of crops. But whether DNA of bacteria is in sweet potatoes only those scientists are knowing. It is not impossible such studies to be financed by companies that create GMO products to justify their unnatural activity.
jazzy_j_man
not rated yet Apr 26, 2015
GMOs are one of those issues where the facts and science are a peripheral issue; it mainly serves to define ego identity. "I'm one of those people/I'm not one of those kind of people" is much, much, much more important to most than any real science.

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