Study On Degradation Of Endogenous And Exogenous DNA In Bt Transgenic Rice During Food Processing

With the rapid development of transgenic technology,more and more genetically modified(GM)crops were commercialized.The effection of the GM crops on the human health and the ecological environment has attracted widely attentions of the public.In this paper,we used genetically modified rice with CrylAb/Ac(TT51-1)as a raw material to assess the degradation of endogenous and exogenous DNA during food processing.The study will provide scientific and theoretical basis for the detection and supervise of transgenic rice food products.The experiment included two parts:The first experiment was designed to study the degradation of endogenous and exogenous DNA in Bt transgenic rice during food processing by conventional PCR.GM rice with Crv1Ab/Ac(TT51-1)and non-GM rice(Minghui 63)were used as raw materials to produce different processed foods,including boiled rice,autoclaving treated rice,rice crackers,sweet rice wine.Different PCR primers were designed by Primer Premier 5.0 software to amplify the endogenous gene SPS,and exogenous genes or elements which are actin1 promoter,Cry1Ab/Ac,NOS terminator,and event-specific 3'lunction sequence.The result showed that autoclave had more effective on the degradation of endogenous and exogenous DNA than boil of autoclaving treated rice and boiled rice.During rice crackers producing,boiling,1st drying and 2nd drying contributed to the initial degradation of endogenous and exogenous DNA of GM rice,and frying was the most severe procedure,followed by baking and microwaving on DNA degradation.During sweet rice wine processing,after the boiling step which resulted in the marked degradation of endogenous and exogenous DNA,there was no further degradation during fermenting for 1 to 4 days.Meanwhile,all fragments less than 200 bp had high stability in the processing.The test showed that different food procedures had diverse effectes on the degradation of endogenous and exogenous DNA of GM rice.The second experiment was designed to study the degradation of endogenous and exogenous DNA in Bt transgenic rice during food processing by real-time fluorescent quatititive qPCR.Primers for fluorescent quatititive PCR were designed to amplify endogenous gene SPS,exogenous genes or elements actin1 promoter,CrylAb/Ac,event-specific 3'junction sequence,and NOS terminator.The results showed that fragments less than 200 bp also degraded during the processing.Degradation rates of the SPS gene,actin1 promoter,CrylAb/Ac,event-specific 3'junction sequence,and NOS terminator were 99.9%,99.9%,99.8%,99.8%,99.9%respectively by frying;98.4%,98.7%,98%,97.9%,98.2%respectively by baking;86.1%,89.5%,88.7%,84.1%,89.3%respectively by microwaving;75.6%,79.5%,77.2%,74.5%,77.1%by fermentation.Thus it could be seen that frying was the most severe procedure,followed by baking,microwaving and fermentation.Degradation rates of the SPS gene,actin1 promoter,Cry1Ab/Ac,event-specific 3'junction sequence,and NOS terminator by boiling were 74.4%,77.6%,76.1%,73.4%,76.9%respectively,while those by autoclaving were 74.9%,80.4%,11.5%,73.8%,77.5%respectively.Compared to boiling processing,autoclaving processing had more effect on the degradation of endogenous and exogenous DNA of GM rice.In addition,when detecting the content of GM components in foods,selecting different exogenous genes as a representative of genetically modified material would gain different results,which depended on the relative stabilities of exogenous genes to endogenous genes.