Roundup Ready™ soybean

The soybean line GTS 40-3-2 was developed to allow for the use of glyphosate, the active ingredient in the herbicide Roundup®, as a weed control option. This genetically engineered soybean line contains a form of the plant enzyme 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) that allows GTS 40-3-2 to survive the otherwise lethal application of glyphosate. The EPSPS gene put into GTS 40-3-2 was isolated from a strain of the common soil bacterium Agrobacterium tumefaciens called CP4 and the form of EPSPS enzyme produced by this gene is tolerant to glyphosate.

Line: A5403

PV-GMGT04

The plasmid PV-GMGT04 contained three transformation cassettes driven by plant promoters: two cp4 epsps genes and a gene encoding ß-glucuronidase (GUS) from E. coli. Only a portion of  this vector was incorporated into event 40-3-2. Southern blot and PCR analysis indicated that only a single transformation cassette containing the EPSPS coding sequence was integrated into the host genome. The largest insert, containing the function CP4 EPSPS gene, contained a deletion in the enhancer region of the E35S promoter and the remainder of the E35S promoter was functional. Analysis also indicated that there was no intigration of segments of the vector backbone, the GUS coding sequence or the CmoVb promoter.

The cp4epsps coding sequence encodes a 455 amino acid protein is terminated by tandem stop codons, and results in the synthesis of the full length and functional  ~46kDa CP4EPSPS protein in Round-up Ready soybean event 40-3-2 as confirmed by western blotting, enzyme-linked immunosorbent assay and EPSPS enzyme activity assays.

The EPSPS enzyme is part of an important biochemical pathway in plants called the shikimate pathway, that is involved in the production of aromatic amino acids and other aromatic compounds. When conventional plants are treated with glyphosate, the plants cannot produce the aromatic amino acids needed to grow and survive. EPSPS is present in all plants, bacteria, and fungi. It is not present in animals, which do not synthesize their own aromatic amino acids. Because the aromatic amino acid biosynthetic pathway is not present in mammals, birds or aquatic life forms, glyphosate has little if any toxicity for these organisms. The EPSPS enzyme is naturally present in foods derived from plant and microbial sources.