Surekha Karudapuram, Ph.D. and David Batey, Ph.D.
MJ Research, Inc., South San Francisco, CA
We present a real-time quantitative PCR (qPCR) protocol for the detection and quantitation of soy genetically modified to be resistant to the herbicide glyphosate. The assay utilizes SYBR Green I (SGI) detection of amplicons of the genetically modified organism (GMO) specific sequences as well as a common soy gene as a reference. The assay can detect GMO materials down to 0.5% (w/w) concentration in foods. The use of SGI for detection makes this protocol readily adaptable for the analysis of other food crops for the presence of GMO material.
A wide variety of food crops have been genetically engineered to contain beneficial traits such as herbicide resistance, disease resistance and insect resistance. Accurate and reliable detection of genetically modified organisms (GMOs) in foods is becoming increasingly important as the demand for labeling of GMO-containing foods increases.
Perhaps the most widely utilized modification that confers herbicide resistance is that which confers resistance to glyphosate [N- (phosphonomethyl)glycine]. Glyphosate is a competititive inhibitor of enolpyruval-shikimate-3-phosphate synthase (EPSPS), which is required for the production of aromatic amino acids by plants.1
To create glyphosate resistance, plants are transformed with a glyphosate
tolerant version of the EPSPS gene from strain CP4 of the soil bacterium
Agrobacterium sp.2, 3 Expression of the CP4 EPSPS in
such modified plants confers resistance to glyphosate, and thus allows