Embryotoxicity of Transgenic Rice TT51 and Cry1Ab Bt Insecticidal Toxin in Rat Post Implantation Whole Embryo Culture

TT51, with a synthetic Cry1Ab/CryAc gene from Bacillus thuringiensis Berliner, was the first genetically modified (GM) plant officially certificated in China. This study was undertaken to investigate potential embryotoxicity of TT51 on rats. Whole embryo culture (WEC) is an effective method for safety evaluation when culture medium, containing substances derived from GM food, is available. Rat embryos explanted from uterus were randomly distributed into 6 groups: Transgenic Rice (TR) group with transgenic rice dietary administration, Parental Rice (PR) group with parental rice dietary administration, Blank Control (BC), Positive control A (PCA) group with Bisphenol A being directly added into the culture medium, Positive control B (PCB) group with Bisphenol A oral administration and Bt protein (BP) group with Bt protein directly added into culture medium. After culturing for 48 h, embryos were scored for growth and differentiation at the endpoint. Embryos in TR group had no significantly lower morphological scores or smaller yolk sac diameter, crown-rump length (CRL) and cranial diameter comparing with those in BC and PR group. Embryos in PCA and PCB group both performed significantly lower developmental parameters and morphological scores than the other three groups. Embryos directly exposed to Bt protein (52 mg/L) exhibited severe morphological anomalies but no significant difference in yolk sac diameter compared with PR, TR and BC groups. In this WEC model, TT51 showed no embryotoxicity to rats although Bt toxin had side effect on embryos when the concentration is equal to the daily intake of Bt protein in TT51 diet. And it also indicated that WEC method can make an option for toxicological assessment of GM food.