The Potential Impact Of Transgenic Cry2Aa Rice On Chrysoperla Sinica Tjedar

Chrysopela sinica Tjedar is one of important natural enemies in multiple crops. Since easily rearedand manipulated in laboratory, they have been widely used as indicator species in assessment ofnon-target effects of insect-resistant transgenic crops. In this study, the seasonal expressions of Cryproteins in different tisssues of transgenic rice lines were analyzed by ELISA, and bioassay systemswere developed to evaluate the poteintial impacts of transgenic rice expressing Cry2Aa on larvae andadults of C. sinica. The results were summarized as follows:(1) ELISA results showed that Cry1Ca protein was significantly differently expressed in differenttissues of Bt rice (T1C-19b), and the content of Cry protein in leaf was higher than in roots and stems.The expression dynamics of Cry1Ca in rice root and leaf were similar: Cry1Ca content is relatively lowin tillering stage, then increased gradually, and reached the peak in jointing stage; in subsequence thecontent declined to the lowest level in heading period with a little increase at filling and maturing stages.In Bt rice stems, the concentrations of Cry1Ca were higher at fiiling and maturing periods compared tojointing stage. The expression dynamic of Cry1Ac/1Ab in Huahui1was similar to Cry1Ca in T1C-19bwith the highest content at jointing stage and lowest level at heading stage. Contrary to Cry1Ca, thehighest levels of Cry1Ac/1Ab were expressed in stems especially at booting and jointing stages with3.7-26.1times higher than in leaves and roots. These data formed foundamental information for furtherassessment of environmental effects of the Bt rice lines.(2) A bioassay system was developed for assessing the toxicity of insecticidal proteins on C. sinicalarvae using sugar solution and aphids as food. To confirm the sensitivity of the system, sugar solutioncontaining different concentrations of potassium arsenate (PA) was fed to lacewing larvae.Dose-responses were found for the life-table parameters of insects with the increase of PAconcentrations. The toxicity of Cry2Aa to lacewing larvae was assessed using the experimental systemand the results showed that feeding Cry2Aa at high dose of500μg/ml did not affect the development oflacewing larvae. This demonstrates that planting of Bt rice expressing Cry2Aa will not pose a risk onlarvae of C. sinica.(3) Laboratory bioassays were conducted to evaluate the potential impacts of Cry2Aa-expressingtransgenic rice (T2A-1) pollen on fitness of adult C. sinica, and no negative effects were found on adultswhen feeding Bt rice pollen. To confirm that C. sinica adults are not sensitive to Cry2Aa protein, theywere fed with an artificial diet containing Cry2Aa protein at an approximately10times higherconcentration than in rice pollen. Artificial diet containing PA was used as a positive control. Nodifference was detected for any life-table parameters tested between Cry2Aa-containing and pure diet.In contrast, there were adverse effects on C. sinica in PA treatment. These results demonstrate thatgrowing Bt rice expressing Cry2Aa protein will pose a negligible risk to adult C. sinica.