Notes

Genetically modified crops offer advantages to the weeds

Wild plants may be capable of resisting herbicides.

Credit to Xiao Yang
A method of genetic modification used extensively to produce crops that are herbicide-resistant has been found to provide advantages to the weedy rice, even in the absence of the herbicide. The findings suggest that this modifications could be beneficial to wild rice varieties and the crops.

A range of crops has been genetically modified so that they become immune to Roundup herbicide glyphosate. Farmers are able to eliminate weeds from their fields with this glyphosate resistance , without damaging their crops.

ラウンドアップ Glyphosate slows the growth of plants by inhibiting EPSP synthase (an enzyme that is involved in the formation of amino acids, and various other molecules). The enzyme can comprise as much as 35 percent or more of a plant’s total mass. Genetic modification employed by Monsanto's Roundup Ready crops, which are based in St Louis (Missouri), generally involves inserting genes into the DNA of a plant to boost EPSP synthase's production. https://www.jacom.or.jp/nouyaku/news/2019/10/191024-39457.php The genes typically come from bacteria that are infected with plants.

This additional EPSP synthase enables plants to counteract the effects from glyphosate. Biotechnology labs have also attempted to make use of the genes of plants to increase EPSP-synthase, partly to take advantage of a loophole in the American system that allows for regulatory approval of transgenes not derived bacterial pests.

There aren't many studies that have examined the possibility that transgenes that confer tolerance may -- once they become weedy or wild relatives by cross-pollinating- increase the plants' longevity and reproductive. "The traditional expectation is that any sort of transgene will confer disadvantage in the wild in absence of any selection pressure because the extra machinery would lower the fitness," says Norman Ellstrand an expert in plant genetics at the University of California in Riverside.

A new study, led by Lu Baorong, an ecologist at Fudan University in Shanghai, is challenging that notion: it shows that a weedy variant of the standard rice plant, Oryza sativa has an impressive fitness boost due to the resistance to glyphosate even when glyphosate has not been used.

Lu and colleagues altered cultivated rice species to enhance its EPSP synthase. The modified rice was crossed with a wild-type relative.

The group then let offspring cross-bred to breed with one-another, creating second-generation hybrids that were genetically identical to their parents with the exception for how many duplicates of the gene that codes for EPSP synthase. As expected, those who had more copies expressed higher levels of the enzyme, and produced more amino acid tryptophan than their unmodified counterparts.

Researchers also found that plants with transgenic genes showed higher rates of photosynthesis and produced more flowers and produced 48-125percent less seeds per plant than nontransgenic hybrids. This was despite the fact that glyphosate wasn't present.

ラウンドアップ Lu suggests that making weedy Rice more competitive may make the problem worse for the farmers around the world who's fields are being infested by the pest.

ラウンドアップ Brian Ford-Lloyd (a UK plant geneticist) claims that if the EPSP-synthase genes are introduced into wild rice, then their genetic diversity, which is vital to preserve could be at risk. The transgene could outcompete natural species. "This is a clear illustration of the highly plausible negative consequences [of GM plantson the surroundings."

There is a popular belief that genetically engineered plants with extra copies or microorganisms genes are less risky than those with only the genes of their owners. Lu says that Lu's study does not support this view.

Certain researchers believe that this finding needs to be reviewed in light of future regulation of crops that have been genetically modified. Ellstrand thinks that biosafety rules may be relaxed because we benefit from a high degree of security from two decades of genetic engineering. "But the research shows that the new technologies require careful examination."

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