Detection of genetically modified soybean and its product tou-kan by polymerase chain reaction with dual pairs of DNA primers

Since genetically modified ( GM) crops and foods began to appear in market, the detection of these GM foods has become an important issue. Efficient and reliable methods are urgently needed to analyze the GM content of a large quantity of foods. However, most foods are processed through heating or cooking, and their proteins are denatured. Therefore, DNA rather than protein is the major target for detecting GM foods. In this report, polymerase chain reaction (PCR) was performed with dual sets of DNA primers, which co-amplified the soybean-specific lectin gene and the transgenic petunia transit peptide sequence (CTP) in the 5' end of the 5-enol-pyruvyl-shikimate-3-phosphate synthase (EPSPS) gene within the same reaction. PCR with these two sets of primers reacted specifically with lectin gene and CTP, and can detect soybean with GM content less than 1%. PCR detecting both lectin gene and CTP was also applied to a soybean-derived product tou-kan, a traditional oriental food. Results indicated that although DNA was partially degraded in tou-kan, this PCR method was still able to detect the presence of EPSPS gene. However, when the DNA within tou-kan was destroyed badly, neither lectin nor EPSPS genes were detected by the PCR suggested here. Finally, an examination procedure for the Roundup Ready soybean was suggested according to the results of PCR with dual pairs of DNA primers. The proposed PCR method has proved to be a reliable and efficient method for detecting the GM content of the processed foods from Roundup Ready soybean.