Difference between revisions of "Team:Goettingen/Background"

The discovery of the weedkiller glyphosate

Glyphosate (N-(phosphonomethyl)glycine) was first synthesized by the chemist Dr. Henri Martin in 1950, while working for the Swiss pharmaceutical company Cilag, which was founded in 1936 in Schaffhausen. Unfortunately (fortunately?), Dr. Martin did find out that glyphosate may serve as a very efficient herbicide (see below). About 20 years later, the American chemist Dr. John E. Franz who was working for the American company Monsanto (recently bought by Bayer) observed that glyphosate specifically inhibits the 5-enolpyruvyl-shikimate-3-phosphate (EPSP) synthase in plants, fungi, bacteria and archaea (Figure 1) (1-4). The EPSP synthase generates the precursor for the de novo synthesis of aromatic amino acids tryptophan, tyrosine and phenylalanine (5). Therefore, inhibition of the EPSP synthase by glyphosate results in the depletion of the cellular levels of aromatic amino acids and death of the organism that is treated with the weedkiller (Figure 1) (1,6-8).

Figure 1. Glyphosate that is present in Roundup specifically inhibits the 5-enolpyruvyl-shikimate-3-phosphate (EPSP) synthase (PDBid: 2QFU), which converts shipmate-3-phosphate (S3P) and phosphoenolpyruvate (PEP) to EPSP. A drop in the cellular levels of the precursor for aromatic amino acid synthesis causes death of the organism that has been treated with Roundup.

The usage of glyphosate

Glyphosate is resistant to chemical hydrolysis, thermal decomposition and photolysis due to a stable C-P bond (9). Moreover, due to the fact that glyphosate is toxicologically safe and that transgenic, glyphosate-resistant crops have been introduced by Monsanto, the herbicide has become the dominant weedkiller worldwide (10-15). The production and usage rate of Glyphosate increasing up to this day (Figure 2). Moreover, given the fact that genetically modified crops that produce glyphosate-insensitive EPSP synthases are tolerated in the united states, glyphosate is the most used herbicide in this country (13).

Figure 2. Glyphosate usage over the last two decades. It has been estimated that the production of glyphosate is increasing with a rate of about 40 tons per year. Adapted from Benbrook (13).

The problem of glyphosate-resistant crops

Due to the intensive application of glyphosate in agriculture, several plant species have become resistant against the herbicide. Please check out the webpage http://www.weedscience.org, which is reporting of herbicide resistant weeds globally. The international survey of herbicide resistant weeds is a collaborative effort between weed scientists in over 80 countries. The main aim of this collaborative effort is to maintain scientific accuracy in the reporting of herbicide resistant weeds globally. The collaborative effort is supported by government, academic, and industry weed scientists worldwide. Moreover, the project is funded by the Global Herbicide Resistance Action Committee and CropLife International.

Other applications for glyphosate

Glyphosate is

The glyphosate controversy

Glyphosate is

References

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