Colin Macilwain,WashingtonHundreds of tonnes of geneticallymodified corn seeds sold to farmersby mistake over the past four yearscontained a gene for antibiotic resis-tance, Nature has learned. Therelease of such genes into the envi-ronment is sometimes consideredinadvisable, as there is a smallchance that they could flow fromcrops to microorganisms and spreadproblems of antibiotic resistance.

The Swiss biotechnology com-pany Syngenta admitted last weekthat it had accidentally released avariety of corn (maize) called Bt10between 2001 and 2004. Like othercrops with the name Bt, this corn hadbeen genetically modified to pro-duce a protective pesticide. But Bt10has not been approved for sale byregulatory agencies.

Officials at the company last weekargued that Bt10 is basically identicalto Bt11 corn, which has been approved forsale (see Nature 434, 423; 2005). But thisweek, Sarah Hull, a spokeswoman for Syn-genta,confirmed that a marker gene that con-fers resistance to ampicillin, a commonlyused antibiotic, was present in the Bt10 seeds. She adds that this gene would not havebeen active in the corn plants that grew fromthe seeds.

Antibiotic-resistance genes are widelyused as ‘tags’ during the production ofgenetically modified crops, to help breedersidentify and preserve desirable strains. Butthe genes are often removed before the seeds enter the food chain. The presence ofthe marker gene in Bt10 corn was noted in a2003 advice notice from a UK governmentcommittee, the Advisory Committee onReleases to the Environment, which wasusing Bt10 as a comparison to prove that

there were no marker genes in Bt11 corn.Critics have expressed surprise that nei-

ther Syngenta nor the US EnvironmentalProtection Agency (EPA) announced thepresence of the marker when they admittedthat the release of Bt10 had taken place.“It isquite scandalous,” says Greg Jaffe, head ofthe biotechnology project at the Center forScience in the Public Interest, a pressuregroup in Washington DC. “This shows thatthe government and the company are notbeing forthright.”

Hull says that the company didn’t men-tion the gene’s presence because “it wasn’t rel-evant to the health and safety discussion”.Sheadds that the antibiotic-resistance genes havebeen around for a long time. “They’ve beenstudied extensively, and they pose no risk tohumans or animals,” she says. Regulators saythat the genes present a very small risk to

human health, either directly — if inthe stomach of a patient on anti-biotics, for example — or indirectlythrough gene flow into microbes.

Michael Rodemeyer, director ofthe Pew Initiative on Food andBiotechnology, a think-tank inWashington DC, says that the pres-ence of such genes would be unlikelyto see a crop declared unsafe in theUnited States — but adds that itcould cause problems in Europe.

In a ruling published last April,for example, the European FoodSafety Authority, which advisesEuropean Union governments onfood issues, said that marker genesconferring resistance to ampicillin“should be restricted to field trialsand not be present in geneticallymodified plants placed on the mar-ket”. And the Codex AlimentariusCommission, the internationalfood-standards body, has urged the

agricultural biotechnology industry to usealternative methods to refine geneticallymodified strains in the future.

The EPA,which is jointly investigating therelease of the Bt10 corn with the US Depart-ment of Agriculture, declined to say what itknew about the antibiotic-resistance marker.“What the company told us and when aboutthe marker gene is part of our ongoing inves-tigation and we are not able to discuss it at thistime,”the agency said in a statement.

“I think they’ve done a terrible job,” saysMargaret Mellon, head of the food and envi-ronment programme at the Union of Con-cerned Scientists in Washington DC,referringto both Syngenta and the government agen-cies. “There are lots and lots of unansweredquestions,and the longer they remain,the lessconfidence people are going to have in thetechnology and in the regulatory system.” ■

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Stray seeds had antibiotic-resistance genes

Deal paves way for Congress vote on stem-cell rulesErika Check,WashingtonThe US Congress looks set to vote onwhether to loosen the restrictions thatcurrently govern human embryonic stem-cell research.

Under an agreement reached earlier thismonth, the Republican leadership of theHouse of Representatives will for the firsttime allow the body to debate and vote onwhether to change the regulations.

The current rules, which were announcedby President George W. Bush on 9 August2001, prohibit the use of federal money to pay for research on human embryonic

stem-cell lines created after that date.Congressman Mike Castle (Republican,

Delaware), who favours easing therestrictions, says that he has reached a deal with Republican leaders Roy Blunt(Missouri), Eric Cantor (Virginia) andHouse speaker Dennis Hastert (Illinois).“My sense is that the speaker means to havea legitimate debate and a vote on whether toopen up the policies on embryonic stem-cellresearch,” Castle says.

Until now, the Republican leadership has opposed a review of Bush’s rules. Butdevelopments since the policy was

announced have convinced some prominentRepublicans, including Senator Orrin Hatch(Utah), to reconsider. Scientists have saidthat there are not as many cell lines availableas the president initially said there would be.And the lines have all been made or grownon animal cells, which means that they willnot be suitable for clinical trials in people.

Castle claims that a 100 million peoplecould benefit from the research. “I think the leadership understands the importanceof that,” Castle says, “and frankly some ofthem are probably in favour of it quietly,if not openly.” ■

Keeping track: antibiotic-resistance genes are often used as markersduring the production of transgenic crops such as Bt corn.

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