Notes

Benefits of genetically modified plants over the weeds

Wild plants may be resistant to herbicides.

Credit: Xiao Yang
A common method of genetic modification used to make crops more resistant to herbicides has been shown to offer advantages over the weedy varieties of rice. This suggests that the effects of such modifications could extend beyond the confines of farms out into the wild.

Many varieties of crops are modified genetically to resist glyphosate, a herbicide that was first sold under the trade name Roundup. Farmers can eliminate most herbicides from their fields by using glyphosate, without harming their crops by having this resistance.

Glyphosate prevents plant growth by blocking EPSP synthase (an enzyme that plays a role in the production of specific amino acids, and other molecules). The enzyme can be as large as 35 percent or more of a plant’s total mass. The genetic-modification technique is used in, for instance, 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 boost EPSP synthase synthase synthase production. The genes are often derived from bacteria that have caused the infection of the plant.

This additional EPSP synthase allows the plant to withstand the effects from glyphosate. Biotechnology labs have also tried to create EPSP synthase with more plant-based components than bacteria using genes taken from plants. ラウンドアップ was used to take advantage of a loophole found in US law which allows the approval of regulatory authorities for organisms that are not derived from bacterial parasites.

A few studies have looked into the possibility that transgenes that confer glyphosate tolerance could -- after they become weedy or wild relatives via cross-pollinating -enhance the plant's survival and reproduce. Norman Ellstrand, a University of California plant geneticist, says that without selection pressure, any kind of transgene would be expected to confer disadvantage on wild plants. The extra machinery would lower fitness.

Lu Baorong is an ecologist in Fudan University Shanghai. His research shows that resistance to glyphosate is a major fitness benefit, even though it's not applied.

Their research was published in 1. Lu and his collaborators genetically modified cultivated rice to increase its EPSP synthase expression , and then crossed it with a weedy relative.

ラウンドアップ let the offspring of crossbreeding to cross-breed with each other to create second-generation hybrids. https://myspace.com/roundup44rfc were genetically identical with the exception of the amount of EPSP synthase genes they had. The researchers found that the hybrids that had more copies of the gene encoding EPSP synthase expressed more enzyme and produced more tryptophan as expected.

ラウンドアップ discovered that transgenic hybrids were photogenic, had more seeds per plant and yielded 48-125 percent higher yields of seeds than non-transgenic varieties.

Lu suggests that making weedy Rice more competitive could increase the risk for the farmers around the globe whose fields are being ravaged by the pest.

"If the EPSP-synthase gene is introduced in the wild rice plant, their genetic diversity, which is really essential to protect, could be threatened because the genotype with the transgene will outcompete the natural species" Brian Ford-Lloyd an expert in plant genetics at the University of Birmingham, UK. This is among the most evident examples of likely negative effects of GM crop] on the environment."

The research also challenges the notion that genetically modified crops containing extra copies of their genes are less risky than crops that have microorganism genes. Lu says, "Our study shows this is not necessarily true."

Researchers say their findings require an overhaul of how genetically modified crops will be regulated in the future. Ellstrand states that "some people now believe that biosafety regulation could be relaxed due to our the most comfort with genetic engineering for the past two decades." "But the study proved that new products require careful evaluation."


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