Ecological Safety Of Transgenic Cry2A And Cry1C Rice Lines For The Honey Bee, Apis Mellifera Ligustica

Honey bee is an important economic and social insect, and it has been traditionally selected as a surrogate species in the regulatory risk assessment of genetically modified crops. In this study, a comprehensive analysis were conducted to assess the poteintial impacts of two Bt rice lines(T2A-1, T1C-19) on the honey bee Apis mellifera ligustica. The results were summarized as follows:1. Based on the reported diets and rearing methods, a dietary exposure assay have been developed for assessing the direct toxicity of insecticidal compounds to A. mellifera ligustica larvae. The sensitivity and validation of the system was confirmed using SBTI as a positive compound which was toxic to A. mellifera ligustica.2. Using the established assay, the potential toxicity of Cry1 C and Cry2 A proteins from Bacillus thuringiensis(Bt) to A. mellifera ligustica larvae was assessed, where the 2-d bee larvae were fed artificial diets containing Cry1C(50 μg/g) or Cry2A(400 μg/g). And the assay used the soybean trypsin inhibitor(SBTI) as a positive control and bovine serum albumin(BSA) as a negative control. The results revealed that survival and development were unaffected, the enzymatic activities(t-Pro, TPS, AMP, α-NAE) of A. mellifera ligustica larvae were not altered and their midguts brush border membranes(BBMs) were not damaged when larvae were fed BSA(400 μg/g), Cry1C(50 μg/g), or Cry2A(400 μg/g). However, the survival rate was decreased, the development time was prolonged significantly, the enzymatic activities were increased and BBMs were damaged when A. mellifera ligustica larvae fed on diets contained SBTI(1 mg/g). Further more, PCR-DGGE experiments were conducted and found that ingestion of Cry2 A or Cry1 C protein did not affected the structure of bacterial community. These results demonstrate that A. mellifera ligustica larvae are not sensitive to high concentration of Cry1 C or Cry2 A.3. The effects of pollen of two Bt rice lines T2A-1 and T1C-19 on 2-d larvae of A. mellifera ligustica were assessed using the established assay. When fed on the artificial diets containing Bt rice(T2A-1 or T1C-19) pollen, survival, development time and weight of mature larvae were not significantly affected, while effects on the enzymatic activities(t-Pro, TPS, AMP, α-NAE) of larvae were detected.4. After fed with 50%(w:w) sucrose solution containing Cry2A(400 μg/g), Cry1C(50 μg/g) protein or BSA(400 μg/g, as a negegtive control) for 5 weeks under laboratory conditions, survival and the mean diameters of hypopharyngeal gland acini of A. mellifera ligustica adults were not significantly affected compared to the adults that fed pure diets(50% sucrose solution). And the enzymatic activities(t-Pro, TPS, AMP, α-NAE) of A. mellifera ligustica adults were not affected by Cry protein feeding. On the contrary, survival rate was significantly decreased when feeding on the diets containing high concentraion of SBTI(10 mg/g); when ingesting the surcose solution containing low concentraion of SBTI(1mg/g), survival rate was reduced, the mean diameters of hypopharyngeal gland acini were obviously smaller than that of pure diet treatment, and the enzymatic activities(t-Pro, TPS, AMP, α-NAE) were aslo affected. Likewise, fed with sucrose solution containing Cry2A(400 μg/g) or Cry1C(50 μg/g) protein for 5 days, 10 days or 15 days, the structure of bacterial community in the gut of bee adults was not significantly affected using PCR-DGGE analysis.5. When A. mellifera ligustica adults were supplied the diets containing Bt or non-Bt rice pollen, honey and water at the ratio of 5: 4: 1 for 10 days, there were no significant effects on survival rate, the mean diameters of hypopharyngeal gland acini and the enzymatic activities(t-Pro, TPS, AMP, α-NAE) of A. mellifera ligustica adults.6. The results from the current study reveal that planting of the two Bt rice lines(T2A-1 and T1C-19) would have negligible risk on the honey bee, A. mellifera ligustica.