Validation of a Tomato-specific Gene, LAT52, Used As an Endogenous Reference Gene in Qualitative and Real-time Quantitative PCR Detection of Transgenic Tomatoes

Toward the development of reliable qualitative and quantitative Polymerase Chain Reaction (PCR) detection methods of transgenic tomatoes, one tomato (Lycopersicon esculentum) species specific gene, LAT52, was selected and validated as suitable for using as an endogenous reference gene in transgenic tomato PCR detection. Both qualitative and quantitative PCR methods were assayed with 16 different tomato varieties, and identical amplified products or fluorescent signals were obtained with all of them. No amplified products and fluorescent signals were observed when DNA samples from 20 different plants such as soybean, maize, rapeseed, rice, and Arabidopsis thaliana were used as templates. These results demonstrated that the amplified LAT52 DNA sequence was specific for tomato. Furthermore, results of Southern blot showed that the LAT52 gene was a single-copy gene in the different tested tomato cultivars. In qualitative and quantitative PCR analysis, the detection sensitivities were 0.05 and 0.005 ng of tomato genomic DNA, respectively. In addition, two real-time assays employing this gene as an endogenous reference gene were established, one for the quantification of processed food samples derived from nontransgenic tomatoes that contained degraded target DNA and the other for the quantification of the junction region of CaMV35s promoter and the anti-sense ethylene-forming enzyme (EFE) gene in transgenic tomato Huafan No. 1 samples. All of these results indicated that the LAT52 gene could be successfully used as a tomato endogenous reference gene in practical qualitative and quantitative detection of transgenic tomatoes, even for some processed foods derived from transgenic and nontransgenic tomatoes.