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Biodiversity (Communications arising)

Suspect evidence of transgenic contamination (see editorial footnote)


Quist and Chapela1 claim that transgenic DNA constructs have been introgressed into a traditional maize variety in Mexico, and furthermore suggest that these constructs have been reassorted and introduced into different genomic backgrounds. However, we show here that their evidence for such introgression is based on the artefactual results of a flawed assay; in addition, the authors misinterpret a key reference2 to explain their results, concluding that reassortment of integrated transgenic DNA occurs during transformation or recombination.

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Figure 1: Alignment of primers with cauliflower mosaic virus 35S promoter sequences and the ends of inverse polymerase chain reaction (i-PCR) products.


  1. Editorial note

    In our 29 November issue, we published the paper “Transgenic DNA introgressed into traditional maize landraces in Oaxaca, Mexico” by David Quist and Ignacio Chapela. Subsequently, we received several criticisms of the paper, to which we obtained responses from the authors and consulted referees over the exchanges. In the meantime, the authors agreed to obtain further data, on a timetable agreed with us, that might prove beyond reasonable doubt that transgenes have indeed become integrated into the maize genome. The authors have now obtained some additional data, but there is disagreement between them and a referee as to whether these results significantly bolster their argument.

    In light of these discussions and the diverse advice received, Nature has concluded that the evidence available is not sufficient to justify the publication of the original paper. As the authors nevertheless wish to stand by the available evidence for their conclusions, we feel it best simply to make these circumstances clear, to publish the criticisms, the authors' response and new data, and to allow our readers to judge the science for themselves.

    Editor, Nature


  1. Quist, D. & Chapela, I. H. Nature 414, 541–543 (2001).

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  2. Pawlowski, W. & Somers, D. A. Proc. Natl Acad. Sci. USA 95, 12106–12110 (1998).

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  3. Neto, R. B. Nature 402, 344 (1999).

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  4. Jayaraman, K. S. Nature 413, 555 (2001).

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Correspondence to Matthew Metz.

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Competing interests

Matthew Metz has a consulting

position (roughly 5 hours per week) with Tilligen Inc., Seattle,

Washington. Tilligen is developing an alternative technology to

transgenic crops, and could lose financial

advantage as a result of the submitted critique.

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Metz, M., Fütterer, J. Suspect evidence of transgenic contamination (see editorial footnote). Nature 416, 600–601 (2002).

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