[Bt toxic protein expression in insect-resistant transgenic corns and its transfer to and accumulation in Ostrinia furnacalis]

Abstract

Taking the insect-resistant transgenic corn varieties G03-2396 and G03-2739 and the conventional corn variety Suyu 16 as test materials, a bioassay in laboratory was conducted to test their resistance against Ostrinia furnacalis. The Bt toxin expression in different tissues of the two transgenic corns, the ingestion of Bt toxin by the 3rd and 5th instar of O. furnacalis, and the Bt toxin amount in feces of O. furnacalis larvae fed with Bt corns were analyzed by using enzyme-linked-immunosorbent-assay (ELISA). It was found that the central leaves of both G03-2396 and G03-2739 had great toxicity to O. furnacalis larvae. After fed with the central leaves for 6 d, the survival rate of neonate larvae was less than 3%, and that of the 3rd instar larvae was less than 70%. Female ears had smaller toxicity than central leaves. The Bt toxic protein was detected both in the leaves and in the female ears of the two transgenic corns, but its content was higher in central leaves than in female ears. The Bt toxic protein expression level was in order of G03-2739 central leaf (39.6 microg x g(-1) FM) > G03-2396 central leaf (26.1 microg x g(-1) FM) > G03-2396 female ear (17.0 microg x g(-1) FM) > G03-2739 female ear (14.6 microg x g(-1) FM). When fed with central leaf or female ear, the Bt toxic protein amount in the 3rd instar larvae was significantly higher than that in the 5th instar larvae. For the same age instar larvae, the Bt toxic protein content was significantly higher after fed with central leaf than fed with female ear, so did the Bt toxic protein content in larvae feces, being the highest (10.4 microg x g(-1) FM) for the 5th instar larvae fed with G03-2739 central leaf, and the lowest (2.7 microg x g(-1) FM) for the 3rd instar larvae fed with G03-2739 female ear.