CHARACTERISATION OF THE 3’ INTEGRATION SITE IN MON810 YIELDGARD® MAIZE COMMERCIAL LINES

The interest for the stability and biosafety of the genetically modified (GM) crops has increased in the last 20 years, together with their diffusion on the world market, causing a strong demand for the development of both analysis and detection methods. In Europe, among the mandatory labelling requirements for GM plants and derived food, the analysis of the insertion site and the characterization of the transgene flanking regions are requested. YieldGard® MON810 maize, produced by Monsanto, is one of the major GM crops. It contains the CaMV 35S promoter, the hsp70 intron of maize, the cryI(A)b gene for resistance to lepidoptera, and the NOS terminator. After commercialization, Hernandez and collaborators (2003) evidenced a truncation event at the 3’ end of the cryI(A)b gene with the complete loss of the NOS terminator. Moreover, the 3’ maize genome junction region isolated did not show any homology with known sequences. Here we describe the isolation of a larger portion of the 3’ integration junction from genomic DNA of two MON810 maize lines commercially available in Spain (www.oecd.org/dataoecd/1/48/33999570.PDF) and the molecular characterisation of the insertion site in the genome of Zea mays. Specific primers were designed targeting the 3’ integration junction in the plant amplifying a 475 bp fragment downstream of the sequence previously detected (Hernandez et al., 2003). In silico characterization identified the 3’ flanking region as a putative gene coding for the HECT E3 ubiquitin ligase (Moon et al., 2004). Expression analysis of this region evidenced a read-through transcription giving rise to different RNA variants. Finally, results obtained suggested that the insertion of MON810 cassette in the maize genome caused a complex recombination event.