Horizontal methods for molecular biomarker analysis — Methods of analysis for the detection of genetically modified organisms and derived products — Part 7: Real-time PCR based methods for the detection of CaMV and Agrobacterium Ti-plasmid derived DNA sequences
This document specifies a procedure for the detection of a DNA sequence of the open reading frame five (ORF V) from cauliflower mosaic virus (CaMV) and a procedure for the detection of the DNA sequence of the nopaline synthase (nos) gene from tumour-inducing (Ti) plasmids of phytopathogenic Rhizobium radiobacter (formerly named Agrobacterium tumefaciens). The procedures can be used in the context of screening for genetically modified crop/plants and their derived products to further clarify a positive PCR result for a specific promoter or terminator of CaMV (P-35S, T-35S), or both, and the nos gene (P-nos, T-nos), respectively.
The methods specified in this document will detect and identify naturally occurring CaMV or Rhizobium radiobacter (Ti plasmid) DNA, or both, if present in the sample in the absence of a genetically modified plant event containing the specified target sequences.
Both methods are based on the real-time polymerase chain reaction (PCR) and are applicable for the analysis of DNA extracted from foodstuffs and other products such as feedstuffs and seeds/grains. The application of the methods requires the extraction of an adequate amount of amplifiable DNA from the relevant matrix.
With appropriate calibration material, the CaMV ORF V or nos copy number, or both, can be estimated and compared, respectively, with the estimated copy number for the promoter (P-35S, P-nos) or the terminator (T-35S, T-nos) sequences, or both. Thereby, conclusions are possible about the presence of an unknown genetically modified organism (GMO) in addition to any detected CaMV DNA or Rhizobium radiobacter Ti plasmid DNA, or both, in a test sample.
