Durham University Background
Glyphosate based herbicides are the most widely used herbicides in agriculture and also play an important role in public amenity, sports & leisure and home & garden use. Glyphosate acts on the shikimate pathway, inhibiting the enzyme 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), which catalyses the reaction of shikimate-3-phosphate (S3P) and phosphoenolpyruvate (PEP) to form 5-enolpyruvyl-shikimate-3-phosphate (EPSP), resulting in the upstream accumulation of shikimate and the depletion of chorismate, an important precursor for amino acid biosynthesis.
Due to the extensive use of glyphosate, there has been a rise in the incidence of resistance in weed species. For example, in the US there are some 22 “super weed” species that are believed to affect millions of acres of agricultural land.
Researchers at Durham University have been investigating the shikimate metabolic pathway and the importance of metabolite accumulation in that pathway in relation to the effectiveness of glyphosate and related herbicides. In normal shikimate pathway catalysis, EPSPS first binds S3P in the active site and then this EPSPS-S3P complex binds PEP. Glyphosate is a molecular mimic of PEP and competitively binds to the EPSPS-S3P complex and therefore can block EPSP catalysis resulting in the arrest of the shikimate pathway and the depletion of chorismate. In addition the inventors have found evidence that high levels of metabolic intermediates upstream of EPSPS are siphoned by biochemical reactions in which toxic metabolites are synthesised activating chlorosis and cell death.
In glyphosate resistant weeds, flux through the shikimate pathway continues unimpeded in the presence of glyphosate and plants grow normally. The Durham University researchers have found that if PEP is sequestered and/or shikimate pathway intermediates are supplied, the formation of the EPSPS-S3P complex is increased which leaves glyphosate to bind to the complex with little competition and a resistant weed can become susceptible to glyphosate ( and ).
Stage of Development:
Effectiveness of the shikimate pathway intermediates in combination with glyphosate has been shown on glyphosate resistant Conyza sumatrensis (white horseweed). Also, treatment of Arabidopsis plants has shown the requirement for reduced rates of glyphosate.
Overcoming glyphosate resistance
Reduced use of glyphosate for suppressing weeds
Increased effectiveness of glyphosate
Durham University is seeking expressions of interest from suitably positioned industry partners to take forward the commercial development of this herbicide composition technology.
Commercial partner, development partner or licensee of the herbicide technology.
[_Header image attribution: Spot spraying problem weeds is the preferred method of weed control rather than general application of pesticides over the entire yard. / Lynn Betts / _http://www.publicdomainfiles.com/show_file.php?id=13477257676240__ / CC0__]