Detection of recombinant DNA of genetically modified (GM) soybeans in heat-treated GM soybeans and commercial natto

We examined the detection of recombinant DNA of genetically modified (GM) soybeans in heat-treated GM soybeans and commercial natto. Genomic DNA was extracted from heat-treated GM soybeans and natto using the cetyltrimethylammonium bromide (CTAB) or alkaline lysis methods. First, primer pairs amplifying the junction region between CTP and CP4EPSPS in recombinant soybean were designed; they gave PCR products of band sizes, 100, 110, 120, 130, 140, and 150 bp. When DNA solution extracted from heat-treated GM soybeans by the alkaline lysis method was applied to polymerase chain reaction (PCR), PCR products of the expected 100, 110, 120, 130, 140, and 150 bp were detected by agarose gel electrophoresis. However, PCR products were not detected in DNA extracted from heat-treated GM soybeans by the CTAB method, and no PCR products were detected in either extract from natto. Next, PCR using primer pairs amplifying the junction region between NOS and part of CP4EPSPS were designed; they gave PCR products of 100, 110, 120, 130, 140, and 150 bp. The expected PCR products from all DNA extracts were detected (heat-treated GM soybeans by CTAB, 100–140 bp; heat-treated GM soybeans by alkaline lysis, 100–150 bp; natto by CTAB, 100–130 bp; and natto by alkaline lysis, 100–150 bp). These results indicate that judicious selection of DNA extraction methods and target sequences is important to detect DNA from natto and recombinant DNA can be detected in natto.