Detection and copy number estimation of the transgenic nucleotide sequences in an unknown GM event of Oryza sativa

Abstract

The present study was designed to establish a qualitative detection method based on conventional and real time PCR assay to screen the commonly grown rice varieties for the presence of the cry1Ac gene. The detection of genetically modified rice in the screening process would necessitate accurate assay development and precise qualitative PCR tests complying with established procedures for the detection and characterization of transgenes in food grains. Such assay would not only enable the monitoring of transgene flow in local agricultural environment but also the characterization of different plant species produced with this transgene and its regulatory components. Thus, a reliable and quick screening assay was established for the qualitative detection of the transgene along with the promoter and selectable marker gene in genetically modified rice. By conventional PCR, a fragment of 215 bp was amplified with gene specific primers of cry1Ac. Primers for other transgenes such as gna and bar were also employed; however, no amplification was detected. The presence of the p35s, sps, and nptII genes was confirmed by qualitative real-time PCR. The specificity of the respective PCR products was checked through melt peak curve analysis. Sharp and precise melting temperatures indicated the presence of a single kind of PCR product in correspondence to each of the primers used. Moreover, the copy number of cry1Ac was estimated by ΔΔCT method. It is proposed that the primer sets and experimental conditions used in this study will be sufficient to meet the requirements for molecular detection and characterization of the cry1Ac transgene and affiliated sequences in sorting out conventional rice varieties from the ones which are genetically modified. It will also help to monitor the ecological flow of these transgenes and other biosafety factors.