Event-specific Qualitative and Quantitative Polymerase Chain Reaction Methods for Detection of Insect-resistant Genetically Modified Chinese Cabbage Based on the 3′-junction of the Insertion Site

Transgenic Chinese cabbage 416-3 was developed in Korea by a transformation event involving modified insect-resistant gene (cry1Ac1). To monitor unintended release of genetically modified (GM) Chinese cabbage in the future, as well as to meet GM-labeling requirements, the development of a reliable method for detection of GM cabbage is requisite. To develop qualitative and quantitative polymerase chain reaction methods for the insect-resistant GM Chinese cabbage, a cytosolic glutathione reductase (BcgGR1) gene was used as the endogenous reference gene. Primer pairs CGR-1/-2, amplifying the Chinese cabbage endogenous gene, yielded an expected amplicon of 121 bp, whereas no amplified product was observed when DNA samples from seven non-cabbage plants were used as templates. The event-specific primer pairs amplifying the junction site between the endogenous genome sequence and the transferred DNA of GM event 416-3, produced amplicons of desired size by qualitative polymerase chain reaction (PCR) assay. An event-specific quantitative PCR detection method was established using a TaqMan probe and a standard plasmid as a reference molecule, which contained both endogenous and event-specific sequences. For the validation of this method, three different compositions of w/w mixed samples (containing transgenic DNA at 5, 1, and 0.5% of total DNA in the control samples) were quantified. The precision, expressed as standard deviation (SD) and relative standard deviations (RSD), deviated by 0.03-0.26% and 4.75-8.06%, respectively. These results clearly demonstrate that the PCR methods developed herein can be used for event-specific qualitative and quantitative testings of insect-resistant GM Chinese cabbage.