Genetic engineering has achieved great economic value in the cultivation of crops that are tolerant to herbicides, especially glyphosate. (Glyphosate is a relatively safe, cheap, and environmentally harmful herbicide.) Monsanto has a patent for a glyphosate-tolerant plant, but its competitors are trying to get into this area. in. At Science on May 21, a research team introduced a new method for the cultivation of plants that are resistant to glyphosate. If this technology enters the market, it will reduce the price of genetically modified crops and promote further innovation. Glyphosate inhibits an important enzyme used in the production of amino acids in plants. Monsanto has produced glyphosate resistance by adding a glyphosate-influenced microbial-derived isoenzyme gene to crops. This technology has achieved significant success on several crops, especially in soybeans and cotton. Researchers at Verdia Inc. and Maxygen Inc. and Pioneer Hi-Bred International Inc. find clues from a different technique -- that is, the use of microbial enzymes to modify a product called glufosinate (glufosinate). Herbicides are thus expected to yield glyphosate-resistant crops from another method. First researchers began looking for an enzyme that could break down glyphosate. Hundreds of microorganisms were screened in a medium containing different concentrations of glyphosate. The researchers found the most effective soil microorganism, Bacillus licheniformis. The researchers identified 3 genes encoding glyphosate N-acetyltransferase (GAT). In order to speed up the search for the most effective enzymes, the researchers fragmented and recombined the genes, transformed bacteria, and screened for more efficient acetylated genes. After 11 rounds of screening, one enzyme obtained was 10,000 times more efficient than the original. The maize carrying this gene was able to tolerate glyphosate at 6 times the usual concentration, and had no significant effect on the health and yield of the plants. Linda Castle of Verdia stated that there is enough commercial potential and GAT should be effective in other crops. Preliminary studies have shown that by-products of this enzyme, like glyphosate, are non-toxic to mammals. Stephen Duke of the US Department of Agriculture in University, Mississippi said that this method of discovering new enzymes is fast and effective. "But it will take at least five years before this GM crop can compete with Monsanto's glyphosate-tolerant crop," predicts Jonathan Jones of John Innes Centre (in Norwich, UK). But if this new method does succeed, it will stimulate agricultural biotech companies to conduct more in-depth studies to increase crop yields.