转Cry抗虫基因玉米对家蚕的安全性评价

家蚕可能通过取食漂移到桑叶上的玉米花粉从而受到转基因玉米中表达的Cry蛋白的影响。实验采用室内生物测试的方法评价了转cry1Ab和cry2Ab基因玉米GAB-3花粉对家蚕可能产生的影响,并采用在饲料中掺入蛋白的方式检测了转基因玉米中广泛使用的6种Cry杀虫蛋白对家蚕的毒性。当桑叶上GAB-3花粉密度为50粒·cm^-2时,对家蚕幼虫存活率无显著影响,达500粒·cm^-2时,家蚕14 d存活率为0;以10粒·cm^-2的GAB-3花粉饲喂家蚕幼虫7 d对其体重无显著不利影响,但延长饲喂时间或者当GAB-3花粉密度为50粒·cm^-2时,家蚕的体重显著低于对照组;转基因和非转基因玉米花粉处理14 d或更长时间的家蚕体重均低于无花粉处理组。与非转基因对照处理组相比,低于100粒·cm^-2的转基因玉米GAB-3花粉处理组家蚕的化蛹率、茧重、茧壳重和蛹重无显著差异,转基因玉米和非转基因玉米花粉处理均会延长家蚕幼虫的发育历期。GAB-3花粉对家蚕7 d的LC₅₀为261.18粒·cm^-2,随着处理时间延长,LC₅₀下降。测试的6种Bt杀虫蛋白对家蚕的毒性依次为Cry1C>Cry1Fa>Cry1B>Cry2A>Cry1Ab>Cry1Ac。目前,在中国接近商业化的转基因玉米中多采用的Bt杀虫蛋白为Cry1Ab和Cry2A,二者对家蚕的毒性较低,并且在实际生产中,家蚕接触到的转基因玉米花粉密度较低,因此转Cry抗虫基因玉米对家蚕的风险较低。

Safety evaluation of Cry-transgenic insect-resistant maize on silkworm,Bombyx mori

Larvae of the domestic silkworm, Bombyx mori(Linnaeus) could be influenced by Cry protein expressed in genetically engineered maize by consuming maize pollen. Laboratory experiments were conducted to evaluate the potential effects of transgenic maize GAB-3 expressing Cry1Ab and Cry2Ab. The toxicity of six purified Cry proteins that have been used in transgenic maize to silkworm were tested using dietary exposure assays. When the concentration of GAB-3 pollen on the leaves of mulberry was about 50 grains·cm^-2, no significant effect was detected on the survival rate of the neonate larvae of silkworm. The neonate larvae of silkworm could not survive beyond 14 d when the GAB-3 pollen concentration was about 500 grains·cm^-2. No adverse effect on the larvae weight was detected when they were fed with 10 grains·cm^-2 GAB-3 pollen for 7 days. But when the feeding time was prolonged or the density of GAB-3 pollen was more than 50 grains·cm^-2, the larvae weight was significantly decreased compared with the control larvae. The weight of the larvae decreased when they were fed with GAB-3 pollen or the non-transgenic maize pollen for 14 days or more. There was no significant difference in pupation rate, cocoon weight, pupa weight, cocoon shell weight between larvae fed with GM corn pollen or the non-transgenic corn pollen. Both of transgenic and non-transgenic maize pollen prolonged the development time of the larvae. The LC₅₀ of GAB-3 pollen to the neonate larvae of silkworm was 261.18 grains·cm^-2. While the treating time was prolonged, the LC₅₀ value decreased. Six purified Cry proteins that have been used for plant transformation were tested using dietary exposure assays. The toxicities of the tested six Cry proteins to B. mori were in the order: Cry1C>Cry1Fa>Cry1B>Cry2A>Cry1Ab>Cry1Ac. Cry1Ab and Cry2A were low toxicity to B. mori and they were commonly used in transgenic maize which was approaching commercialization in China. As in actual conditions, maize pollen density consumed by B. mori was lower than in lab, suggesting that the risk of Bt maize pollen on silkworm was negligible.