The risk of crop transgene spread

Mikkelsen, Tina Broby; Andersen, Bente; Jørgensen, Rikke Bagger

doi:10.1038/380031a0

Cited by 256 publications

(144 citation statements)

References 3 publications

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“…It is unlikely that hemizygous plants were overlooked due to low expression of the transgenes, because herbicide resistance is a dominant trait. For example, when the bar gene was introgressed into B. rapa, it was expressed sufficiently strongly to make the host plant glufosinateresistant (Mikkelsen et al, 1996a). Furthermore, we also used immunochemical analyses to detect the presence of the products of the glyphosate-resistance transgene in a portion of the seeds collected at each location, and obtained results (data not shown) completely consistent with those obtained using the progeny.…”

Section: Resultssupporting

confidence: 67%

Monitoring the escape of transgenic oilseed rape around Japanese ports and roadsides

Saji

Nakajima

Aono

et al. 2005

Environ. Biosafety Res.

100

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An investigation was carried out to monitor the escape and spread of oilseed rape (Brassica napus) transgenic plants and the introgression of transgenes to its closely related feral species in Japan. We screened a total of about 7500 feral B. napus, 300 B. rapa, and 5800 B. juncea seedlings from maternal plants in 143 locations at several ports, roadsides, and riverbanks. The presence of glufosinate-resistance or glyphosate-resistance transgenes in these seedlings was confirmed by means of herbicide treatments and also immunochemical and DNA analyses. B. napus plants with herbicide-resistant transgenic seeds were found at five of six major ports and along two of four sampled roadsides in the Kanto District. Transgenic oilseed rape plants have not been commercially cultivated in Japan, suggesting that the transgenes would probably have come from imported transgenic seeds that were spilled during transportation to oilseed processing facilities. No transgenes were detected in seeds collected from B. napus plants growing along riverbanks in the Kanto District or in seeds from closely related species (B. rapa and B. juncea). To our knowledge, this is the first published example of feral, transgenic populations occurring in a nation where the transgenic crop has not been cultivated commercially.

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Section: Resultssupporting

confidence: 67%

Monitoring the escape of transgenic oilseed rape around Japanese ports and roadsides

Saji

Nakajima

Aono

et al. 2005

Environ. Biosafety Res.

100

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“…The appearance of B. napus chloroplasts in one of the B. rapa-like plants (Table 4) is therefore likely to be the outcome of progressive introgression with B. napus as the maternal plant, at least once during the introgression process. As a minimum, two successive hybridisations are needed to produce a B. rapa-like plant with cpDNA from B. napus (Mikkelsen et al, 1996), suggesting that the introgression in the maternal population had been in progress for at least three plant generations (pure species, F 1 and BC 1 ). This is in accordance with previous results (Hansen et al, 2001).…”

Section: Lb Hansen Et Almentioning

confidence: 99%

“…Hypothetically, plastidencoded transgenes could be transferred from B. napus to B. rapa, if B. napus was the female just once in the introgression process (Scott and Wilkinson, 1999). In fact, only two generations of crossing (F 1 , BC 1 ) with B. napus acting as the initial maternal plant could produce B. rapa-like plants, which carry 20 A chromosomes and no C chromosomes (Mikkelsen et al, 1996) and the B. napus chloroplast DNA. Our present findings are the first to show such chloroplast capture in nature.…”

Section: Introductionmentioning

confidence: 99%

Progressive introgression between Brassica napus (oilseed rape) and B. rapa

Hansen¹,

Siegismund

Jørgensen³

2003

Heredity

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We have earlier shown extensive introgression between oilseed rape (Brassica napus) and B. rapa in a weedy population using AFLP markers specific for the nuclear genomes. In order to describe the progress of this introgression, we examined 117 offspring from 12 maternal plants from the introgressed population with the same AFLPmarkers; AFLP data were supported by chromosome counting. We also analysed the offspring with a speciesspecific chloroplast marker and finally evaluated the reproductive system in selected maternal plants. Our results indicated a high outcrossing rate of the introgressed maternal plants. It seemed that B. rapa most often functioned as the maternal plant in the introgression process and that the amount of oilseed rape DNA was highly diminished in the offspring compared to their introgressed maternal plants. However, our analysis of plants from the weedy population indicated that introgression can lead to both (1) exchange of chloroplast DNA between species producing B. rapa-like plants with B. napus chloroplasts and (2) incorporation of B. napus C-genome DNA into the B. rapa genome. Therefore, we question whether it can be regarded as containment to position transgenes in the chloroplast or in specific parts of the nuclear genome of B. napus. Heredity (2003) 91, 276-283.

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“…For example, the frequencies of marker genes in wild sunflowers averaged about 28-38%; in wild strawberries growing within 50 m of a strawberry field, more than 50% of the wild plants contained marker genes from cultivated strawberries 5 . Similarly, transgenic oil seed rape, genetically engineered for herbicide resistance outcrossed with a weedy relative, Brassica campestris (field mustard) and conferred herbicide resistance even in the first back-cross generation under field conditions 6 .…”

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Containment of herbicide resistance through genetic engineering of the chloroplast genome

et al. 1998

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Glyphosate is a potent herbicide. It works by competitive inhibition of the enzyme 5-enol-pyruvyl shiki-mate-3-phosphate synthase (EPSPS), which catalyzes an essential step in the aromatic amino acid biosynthetic pathway. We report the genetic engineering of herbicide resistance by stable integration of the petunia EPSPS gene into the tobacco chloroplast genome using the tobacco or universal vector. Southern blot analysis confirms stable integration of the EPSPS gene into all of the chloroplast genomes (5000-10,000 copies per cell) of transgenic plants. Seeds obtained after the first self-cross of transgenic plants germinated and grew normally in the presence of the selectable marker, whereas the control seedlings were bleached. While control plants were extremely sensitive to glyphosate, transgenic plants survived sprays of high concentrations of glyphosate. Chloroplast transformation provides containment of foreign genes because plastid transgenes are not transmitted by pollen. The escape of foreign genes via pollen is a serious environmental concern in nuclear transgenic plants because of the high rates of gene flow from crops to wild weedy relatives. Keywords agricultural biotechnology; transformation; tobacco; glyphosate Glyphosate is a potent, broad spectrum herbicide that is highly effective against a majority of grasses and broad leaf weeds. Glyphosate works by competitive inhibition of the enzyme 5-enol-pyruvyl shikimate-3-phosphate synthase (EPSPS) of the aromatic amino acid biosynthetic pathway. Synthesis of EPSP from shiki-mate-3-phosphate and inorganic phosphate is catalyzed by EPSPS. This particular reaction occurs only in plants and microorganisms, which explains why glyphosate is nontoxic to other living forms. Use of glyphosate is environmentally safe as it is inactivated rapidly in soil, has minimum soil mobility, and degrades to natural products, with little toxicity to non-plant life forms. However, glyphosate lacks selectivity and does not distinguish crops from weeds, thereby restricting its use. EPSPS-based glyphosate resistance has been genetically engineered via the nuclear genome either by the overproduction of the wild-type EPSPS 1 or by the expression of a mutant gene (aroA) encoding glyphosate-resistant EPSPS 2 . *Corresponding author (daniehe@mail.auburn.edu). HHS Public Access Author ManuscriptAuthor Manuscript Author Manuscript Author ManuscriptIn all of the aforementioned examples, without exception, herbicide-resistant genes have been introduced into the nuclear genome. One common concern is the escape of a foreign gene through pollen dispersal from transgenic crop plants engineered for herbicide resistance to their weedy relatives, creating "superweeds." Dispersal of pollen from a central test plot containing transgenic cotton plants to surrounding nontransgenic plants has been observed at varying distances in different directions 3,4 . The escape of foreign genes through pollen is a serious environmental concern, especially in the case of herbicide resistance genes, b...

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The risk of crop transgene spread

Cited by 256 publications

References 3 publications

Monitoring the escape of transgenic oilseed rape around Japanese ports and roadsides

Monitoring the escape of transgenic oilseed rape around Japanese ports and roadsides

Progressive introgression between Brassica napus (oilseed rape) and B. rapa

Containment of herbicide resistance through genetic engineering of the chloroplast genome

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