Department of Entomology, Cornell University/NYSAES, Geneva, New York, United States of America.
PLoS One. 2011;6(7):e22185. doi: 10.1371/journal.pone.0022185. Epub 2011 Jul 12.
The ladybird beetle, Coleomegilla maculata (DeGeer), is a common and abundant predator in many cropping systems. Its larvae and adults are predaceous, feeding on aphids, thrips, lepidopteran larvae and plant tissues, such as pollen. Therefore, this species is exposed to insecticidal proteins expressed in insect-resistant, genetically engineered cotton expressing Cry proteins derived from Bacillus thuringiensis (Bt). A tritrophic bioassay was conduced to evaluate the potential impact of Cry2Ab- and Cry1Ac-expressing cotton on fitness parameters of C. maculata using Bt-susceptible and -resistant larvae of Trichoplusia ni as prey. Coleomegilla maculata survival, development time, adult weight and fecundity were not different when they were fed with resistant T. ni larvae reared on either Bt or control cotton. To ensure that C. maculata were not sensitive to the tested Cry toxins independent from the plant background and to add certainty to the hazard assessment, C. maculata larvae were fed artificial diet incorporated with Cry2Ab, Cry1Ac or both at >10 times higher concentrations than in cotton tissue. Artificial diet containing E-64 was included as a positive control. No differences were detected in any life-table parameters between Cry protein-containing diet treatments and the control diet. In contrast, larvae of C. maculata fed the E-64 could not develop to the pupal stage and the 7-d larval weight was significantly negatively affected. In both feeding assays, the stability and bioactivity of Cry proteins in the food sources were confirmed by ELISA and sensitive-insect bioassays. Our results show that C. maculata is not affected by Bt cotton and is not sensitive to Cry2Ab and Cry1Ac at concentrations exceeding the levels in Bt cotton, thus demonstrating that Bt cotton will pose a negligible risk to C. maculata. More importantly, this study demonstrates a comprehensive system for assessing the risk of genetically modified plants on non-target organisms.
异色瓢虫（Coleomegilla maculata）是许多作物系统中常见且丰富的捕食者。它的幼虫和成虫都是捕食性的，以蚜虫、蓟马、鳞翅目幼虫和花粉等植物组织为食。因此，该物种暴露于表达杀虫蛋白的抗虫、基因工程棉花中，这些杀虫蛋白来源于苏云金芽孢杆菌（Bacillus thuringiensis）的 Cry 蛋白。本研究进行了三营养级生物测定，以评估 Cry2Ab 和 Cry1Ac 表达棉花对表达 Cry 蛋白的抗虫棉中 Bt 敏感和抗性棉上饲养的烟粉虱幼虫饲养的异色瓢虫（Coleomegilla maculata）的适合度参数的潜在影响。当用抗虫棉或对照棉上饲养的抗性烟粉虱幼虫喂养时，异色瓢虫的存活率、发育时间、成虫体重和繁殖力没有差异。为了确保异色瓢虫不因植物背景而对测试的 Cry 毒素不敏感，并增加危害评估的确定性，将异色瓢虫幼虫喂食人工饲料，其中含有高于棉组织中浓度 10 倍以上的 Cry2Ab、Cry1Ac 或两者的混合物。包含 E-64 的人工饲料被用作阳性对照。在含有 Cry 蛋白的饮食处理与对照饮食之间，在任何生命表参数上都没有差异。相比之下，喂食 E-64 的异色瓢虫幼虫无法发育到蛹期，7 天龄幼虫体重显著负向受到影响。在这两种喂养试验中，通过 ELISA 和敏感昆虫生物测定证实了食物来源中 Cry 蛋白的稳定性和生物活性。我们的结果表明，Bt 棉不会影响异色瓢虫，并且在超过 Bt 棉中浓度时，对 Cry2Ab 和 Cry1Ac 不敏感，这表明 Bt 棉对异色瓢虫的危害可忽略不计。更重要的是，本研究展示了一个用于评估转基因植物对非目标生物的风险的综合系统。
