EMBARGOED—NOT FOR PUBLIC RELEASE BEFORE:
Monday, April 20, 2015
 3:00 PM US Eastern Daylight Time
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Tuesday, April 21, 2015
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 6:00 AM Australian Eastern Time
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Complete list of articles expected to publish in PNAS the week of April 20:
<http://www.eurekalert.org/jrnls/pnas/subject.htm>
IMPORTANT NOTE: The articles listed below will publish on Monday, April 20, 2015.
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
Naturally transgenic sweet potato
Genes from naturally occurring bacteria are found in cultivated sweet potatoes around the
world, according to a study. Agrobacterium bacteria are common plant pathogens that
display the ability to transfer segments of their DNA to plants, a property also used by plant
scientists to produce transgenic or genetically modified crops. Jan F. Kreuze and colleagues
conducted genetic analyses on 291 samples of cultivated sweet potato plants (Ipomoea
batatas) from the Americas, Africa, Asia, and Oceania, nine samples of wild I. batatas plants
from the Americas, and four samples from three related Ipomoea species. The authors
discovered the presence of two DNA regions from Agrobacterium species in the cultivated
samples. One of the bacterial DNA regions coded for genes that were expressed at
detectable levels in all 291 cultivated plant samples, but not in any of the wild plant samples.
The other DNA region was found in 45 of 217 sweet potato genotypes examined, including
both cultivated and wild species. Several of the genes are associated with biosynthesis and
sensitivity to plant hormones. According to the authors, the results suggest that transgenic
DNA may have arisen naturally in the sweet potato by horizontal gene transfer during
infection by Agrobacterium and that the bacterial DNA may have provided traits that were
selected for over thousands of years of domestication.
Article #14-19685: “The genome of cultivated sweet potato contains Agrobacterium T-DNAs
with expressed genes: An example of a naturally transgenic food crop,” by Tina Kyndt et al.
MEDIA CONTACTS: Jan F. Kreuze, International Potato Center, Lima, PERU; tel: +51 1
3496017 extension 3010; e-mail: <CIP-CPAD@cgiar.org>; Lieve Gheysen, Ghent
University, BELGIUM; tel +32 9264 5888, + 32 498 454890; e-mail:
<Godelieve.Gheysen@UGent.be>
Images accompanying this article are available.
http://www.eurekalert.org/jrnls/pnas/14-19685.htm
Image 1 Caption: Different sweet potato cultigens.
Credit: Image courtesy of the International Potato Center (CIP).
Image 2 Caption: Different sweet potato cultigens.
Credit: Image courtesy of the International Potato Center (CIP).