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In nature, resistance to herbicides might confer an advantage to plants.

ラウンドアップ Credit: Xiao Yang
A technique of genetic modification widely used to produce crops that are herbicide-resistant has been shown to give advantages to a weedy form of rice, even in absence of herbicide. This indicates that these modifications may have an impact on the environment beyond farm.

ラウンドアップ A variety of plants are genetically engineered to be resistant to the glyphosate. This herbicide, initially known as Roundup it was released on the market in the year 1996 under the trade name Roundup. This glyphosate-resistant crop allows farmers to wipe out most herbicides in their fields without harming their crops.

ラウンドアップ Glyphosate is a plant-killer by inhibiting EPSP synase which is an enzyme involved in the creation of amino acids as well as other chemicals that comprise about 35% of plant mass. The genetic-modification technique is used for instance, in Roundup Ready plants made by Monsanto Biotechnology Inc., a biotech firm located in St Louis, Missouri. It involves inserting genes into the genome of a plant to increase EPSP synthase-synthase production. Genes are typically derived from bacteria that infect the plants.

ラウンドアップ This extra EPSP synthase enables plants to resist the effects from glyphosate. ラウンドアップ Biotechnology labs attempted to utilize genes from plants to boost EPSP synthase activity. This was partly to exploit a loophole within US law that permits regulatory approval of organisms containing transgenes which have not come from pests of bacteria.

Few studies have looked into the possibility that transgenes, like ones that confer resistance to glyphosate, could increase the resilience of plants to surviving and reproduce once they cross-pollinate with wild or weedy species. Norman Ellstrand is a University of California Riverside plant geneticist. “The expectation is that any kind of transgene could cause disadvantages in the wild, in absence of selective pressure since it could reduce fitness,” Ellstrand said. Lu Baorong (an ecologist at Fudan University, Shanghai) has now questioned that opinion. It shows that resistance to glyphosate provides an impressive fitness boost to the weedy rice crop known as Oryza Sativa even when not in use.

Lu and his coworkers have genetically altered the cultivated rice species to express its EPSP synthase, and then crossed it with the plant that was weedy.

The researchers allowed offspring of crossbreeding to crossbreed with each other, resulting in second-generation hybrids that are genetically identical with each other except for the number of copies of the gene encodes EPSP synase. The ones with more copies expressed greater levels of the enzyme, and produced more of the amino acid tryptophan than the unmodified ones.

Researchers also discovered that transgenics had higher rates, more flowers, and 48-125percent more seeds/plant than nontransgenics.

Lu states that making weedy crops more competitive can create more difficulties for farmers across the world whose crops are affected by the insect.

Brian Ford-Lloyd is an UK plant geneticist and says, “If the EPSP synthase gene is introduced into wild rice varieties their genetic diversity could be at risk, which is crucial because the genotype that has transgene outcompetes the normal species.” “This is a clear illustration of the highly plausible negative impacts of GM plants] on our surroundings.”

This study challenges public notion that genetically modified plants with extra copies of their genes are less dangerous than those containing genes from microorganisms. Lu claims that the research does not contradict this notion.

Researchers have said that this discovery requires reconsideration of the regulation for genetically modified crops. Ellstrand believes that some think that biosafety rules can be relaxed since we have over two decades of genetic engineering. “But the study still indicates that innovative products require careful analysis.”