Safety Assessment Of Genetically Modified Bt Rice On Musculus

Five experiments were employed to evaluate the safety of Bt transgenic rice used as a feed ingredient in the mice diet. Effects of transgenic rice on the serum parameters, organ development, embryonic growth and development, crylAc rice's allergenicity, mtDNA mutation were studied and crylAc gene and crylAc protein were detected in mice tissues.Experiment 1. Effect of transgenic rice on serum parameters and organ development of Musculus.80 six-week-old mice were divided into two groups randomly. One group was fed a diet containing Bt transgenic rice while the other group was fed a diet containing the corresponding non-transgenic rice. Some serum parameters were measured, the post-mortem organ index was calculated and organ analysis were performed at the end of the experiment. The serum parameters and organ index were not significantly different. No histopathological damages were detected in liver,lung and spleen,but small bowel biopsy showed that mice had intestinal adenomatous hyperplasia.Experiment 2. Effect of Bt transgenic rice on the growth and development of mouse embryo. Female mice and male mice in experiment 1 were mated by 1:1, the female vaginal smears were detected every day.The day of sperm detected were recorded as the pregnancy 0d, pregnant rats were sacrificed for autopsy in pregnancy 20 d.And the pregnancy weight gain were observed in mice in each group on 0,3,7,10,13,16,20 d to observe the changes in body weight. Pregnant mice's reproductive capacity were inspected. The fetal weight, number of implantation, the number of live births, still births the number of births the number of absorption were recorded. Live births were recorded sex, weight, body length, tail length and appearance of the availability of deformity.1/2 litter were stained with Alizarin Red to examinate bone project. The other 1/2 litter were fixed with Bouin's solution two weeks and sliced in free-hand for visceral examination.The results showed that the transgenic cry 1 Ac rice had no impact on pregnant rats'weight gain; live litter size examination showed that the appearance of the naked eye, head, limbs, tail, trunk, face, palate and lip had no deformities. It also had no impact on skeletal morphology. A magnifying glass were used to check the organ size, shape and location, there is no difference between the 2 groups.Experiment 3. Bt transgenic rice's allergenicity prediction.Search the full-length amino acid sequence of cry 1 Ac protein at NCBI Web site(http://ncbi.nlm.nih.gov). The cry 1 Ac protein amino acid sequence were matched in SDAP (Structural Database of Allergenic Proteins) database, the results show that cry 1 Ac protein had no homology with known allergenic source, nor six consecutive identical amino acids were found.Searching by the three-dimensional structure comparison tool, then found out that Bt toxin protein's three-dimensional conformation were in common with a variety of bacterial toxins such as colicin A (ColicinA), diphtheria toxin (Diphtheria).They all contain a number of hydrophobic and pro-water lipophilic componented a-helix of a-helix bundle, its length is sufficient to cross the double lipid membranes,.They have a similar mechanism of perforation. Therefore, the transgenic rice with Bt genes may be allergenicital. Experiment 4. Study on mtDNA mutations in mice small intestine mitochondria.Select mtDNA 12S RNA and 16S RNA sequence and design four pairs of primers. Amplify the four mtDNA PCR products, the DNA sequencing results were comparised within mitochondrial gene pool of Musculus and found two consistent meaningful point mutations in the mice small intestine samples feeded with transgenic rice, namely 337G> C(His→Asp) and 1771G>T (Asn→Lys). They may play a synergistic role in the abnormal mitochondrial function, resulting in mice small intestine adenoma hyperplasia symptoms. Experiment 5. Detection of recombinant DNA fragment and crylAc protein in mice tissues.With the development of biotechnology, more and more genetically modified plants were used in feed. People payed great attention on the fate of the recombinant DNA and the protein expressed by recombinant DNA of genetically modified plants in animals. In this study,8 mice of 90 days old were reared on a diet prepared from Bt transgenic rice. The blood, organs and muscle were collected under sterile condition. PCR and ELISA methods were used to detecte the 229bp crylAc gene fragment and crylAc protein in these samples. The results showed that no 229bp crylAc gene fragment and crylAc protein were detected. Therefore, there were no residual of transgenic composition in mice.In conclusion, through a series of studies, no adverse effect was found when the transgenic rice was used in mice diet,and recombinant DNA fragment and crylAc protein were not found in mice tissues. But the mouse small intestine had midgut gland tumor proliferation and mtDNA were detected two significant mutations. Therefore, during the trial period,the Bt transgenetic rice as animal feed is unsafe, but still needs further study. These studies can provide scientific reference data for the transgenic rice used in food.