Nowadays HRC's (herbicide resistant crops), like Round-Up-Ready Cotton, are being developed to make the crops more competitive than weeds. Does the above apprehension sound logical? If yes, then how can we avoid the inevitable danger of gene flow from HRC to weeds?
1. 'Gene flow' is a common phenomena between plants through such as the movement (by wind) of pollens from one plant to hybridize with another plant. Transgenes can be introduced from transgenic plants to non-transgenic plants in such a way. Evidence have showed that herbicide-resistant gene can be transferred from transgenic weeds to their relative weeds.
2. Scientists have tried to device different strategies to retain transgene only in the intended GM plants. For example, the use of pollen-specific promoter to delete the whole transgene cassette inside the pollen using site-specific recombination systems before pollen mature. Except pollens, other pant organs such as fruits (with seeds) and seeds (which carry the transgenes) can be eaten by animals and move the genes to another places. Remove the transgenes before seed forming is also important in this case.
Another way you can contain the transgene in the intended GM by doing genetic transformation on the chloroplast genome, instead of the nucleus genome. So, the pollens will not carry the transgene. The condition is that a good chloroplast transformation protocol should have developed for the crop-of-interest. Please refer to this paper:
Nature Biotechnology 16, 345 - 348 (1998)
Containment of herbicide resistance through genetic engineering of the chloroplast genome
Henry Daniell, *, Rina Datta, Sam Varma, Steven Gray & Seung-Bum Lee
Thanks! dear Yuan-Yeu, for providing me the latest and relevant info on the topic under discussion. Now, the moot point is whether this bio-technique is being used by the MNC's like Monsanto developing genetically modified seeds?
Monsanto had employed site-specific recombinase system to remove 'selectable marker gene (kan-resistance gene)' from a commercialized corn, but I am not aware of removing 'herbicide-resistant gene' from commercial crops.
Most proof-of-concept chloroplast transformation experiments are still limited to the model plant tobacco. An optimum chloroplast transformation protocol is needed for every crop we are interested in before we can accomplish our goals of containment of transgenes in the chloroplast genomes.
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