PCR-ELISA for the CaMV-35S promoter as a screening method for genetically modified Roundup Ready soybeans

Screening of food components using a polymerase chain reaction (PCR) for the presence of genetic elements, such as the widespread cauliflower mosaic virus 35S promoter introduced into genetically modified organisms (GMOs), has become a routine method in modern food analysis. With the aim of developing a high throughput method suitable for automation we established a PCR-enzyme-linked immunosorbent assay (PCR-ELISA). It is based on specific hybridization of an immobilized, biotinylated PCR product with a digoxigenin-labelled internal probe; the label then serves in colorimetric immunodetection. With this fast and convenient method laborious blotting procedures and the use of hazardous ethidium bromide in gel staining are avoided. The optimized protocol for this PCR-ELISA allows the detection of as little as 0.1 ng amplicon in only 2 h. With this new technique we analyzed whole Roundup Ready soybeans as well as soybean flour with GMO contents ranging from 0.1% to 2%.