Amplification of the aroA gene from Escherichia coli results in tolerance to the herbicide glyphosate

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Abstract
The predominant cellular target of the herbicide glyphosate is thought to be the enzyme 5-enolpyruvylshikimate-3-phosphoric acid synthase (EPSP synthase). As a means of biologically testing this finding, a segment of DNA from E. coli that encodes this enzyme was cloned. Clones carrying the gene for EPSP synthase were identified by genetic complementation. Cells containing multicopy plasmid carrying the EPSP synthase gene overproduced the enzyme 5- to 17-fold and exhibited at least an 8-fold increased tolerance to glyphosate. These experiments provide direct biological evidence that EPSP synthase is a major site of glyphosate action in E. coli and that, in an amplified form, it can serve as a selectable glyphosate resistance marker.