Glyphosate-Tolerant Crops: Genes and Enzymes¹

This review focuses on the genes for the enzymes 5-enolpyruvyl-3-phosphoshikimic acid synthase (EPSPS) and the glyphosate oxidoreductase (GOX). These genes have been used to genetically engineer plants that are resistant to the herbicide glyphosate. Overproduction of glyphosate-lnsensitive EPSPS in transgenic crops has been used to overcome the deleterious effects of this herbicide. The introduction into plants of GOX also confers glyphosate tolerance to plants and augments the tolerance of transgenic plants already expressing a glyphosate tolerant EPSPS. These genes also provide a method for selecting transformed plant tissue using the glyphosate tolerance as the selectable marker in the presence of inhibitory concentrations of glyphosate. Glyphosate tolerant transgenic plants of beet, cprn, cotton, lettuce, poplar, potato, rapeseed, soybean, tobacco, tomato, and wheat have already been field tested and are entering agriculture.