Soya is one of the most widely grown GM crops. Most soya grown in the USA, Brazil and Argentina is genetically modified.Herbicide-tolerant soya
The main GM soya is tolerant to the herbicide glyphosate. Glyphosate kills plants by inhibiting the enzyme EPSPS, which is needed to make the aromatic amino acids (phenylalanine, tyrosine and tryptophan). Without them the plant cannot make proteins and dies. Animals do not have this enzyme.GM soya contains a gene for a version of EPSPS from a strain of the bacterium Agrobacterium that glyphosate does not inhibit. The soya can therefore still make aromatic amino acids when sprayed, while the weeds around it die.Benefits: farmers can control weeds with one or two sprays of a single herbicide, which also allows less ploughing and so reduces soil erosion.Problems: heavy reliance on glyphosate has selected for glyphosate-resistant weeds in many areas, so farmers have had to use more or different herbicides.Other GM soya
• High oleic soya produces a healthier oil because a gene for a fatty acid desaturase enzyme has been silenced, so less polyunsaturated fat is made. The oil is more stable for frying and forms fewer trans fats.
• Bt soya produces an insecticidal toxin.A warning example
In the 1990s, soya was given a gene from Brazil nuts to raise its methionine content. Tests showed the protein could trigger an allergic reaction in people with nut allergy, so the product was abandoned. This shows why new GM proteins are tested for allergenicity.
The main GM soya is tolerant to the herbicide glyphosate. Glyphosate kills plants by inhibiting the enzyme EPSPS, which is needed to make the aromatic amino acids (phenylalanine, tyrosine and tryptophan). Without them the plant cannot make proteins and dies. Animals do not have this enzyme.GM soya contains a gene for a version of EPSPS from a strain of the bacterium Agrobacterium that glyphosate does not inhibit. The soya can therefore still make aromatic amino acids when sprayed, while the weeds around it die.Benefits: farmers can control weeds with one or two sprays of a single herbicide, which also allows less ploughing and so reduces soil erosion.Problems: heavy reliance on glyphosate has selected for glyphosate-resistant weeds in many areas, so farmers have had to use more or different herbicides.Other GM soya
• High oleic soya produces a healthier oil because a gene for a fatty acid desaturase enzyme has been silenced, so less polyunsaturated fat is made. The oil is more stable for frying and forms fewer trans fats.
• Bt soya produces an insecticidal toxin.A warning example
In the 1990s, soya was given a gene from Brazil nuts to raise its methionine content. Tests showed the protein could trigger an allergic reaction in people with nut allergy, so the product was abandoned. This shows why new GM proteins are tested for allergenicity.