Agroscope, Research Division Agroecology and Environment, Reckenholzstrasse 191, 8046 Zurich, Switzerland.
Agroscope, Research Division Agroecology and Environment, Reckenholzstrasse 191, 8046 Zurich, Switzerland.
Ecotoxicol Environ Saf. 2021 Apr 1;212:111967. doi: 10.1016/j.ecoenv.2021.111967. Epub 2021 Jan 29.
Non-target effects of genetically engineered (GE) plants on aquatic Daphnia magna have been studied by feeding the species with different maize materials containing insecticidal Cry proteins from Bacillus thuringiensis (Bt). The results of those studies were often difficult to interpret, because only one GE plant was compared to one related non-GE control. In such a setting, effects of the Cry proteins cannot be distinguished from plant background effects, in particular when the test species is nutritionally stressed. In the present study, we tested the suitability of three different maize materials, i.e., flour, leaves and pollen, from five diverse non-GE maize lines (including EXP 258, a breeding line that is closely related to a SmartStax Bt maize) as exclusive food sources for D. magna. The parameters recorded included survival, sublethal endpoints such as body size, number of moltings to first offspring, time to first offspring, number of individuals in first clutch, total number of clutches, total number of offspring, average number of offspring per clutch, and population measures such as net reproductive rate R, generation time T and intrinsic rate of increase r. The results showed that D. magna can survive, grow and reproduce when fed only maize materials, although the performance was poorer than when fed algae, which indicates nutritional stress. Large differences in life table and population parameters of D. magna were observed among the different maize lines. Our results suggest that confounding effects caused by nutritional stress and plant background might explain some of the conflicting results previously published on the effects of Bt crops on D. magna. Using 95% confidence intervals for the means of the five maize lines for all measured parameters of D. magna performance in our study, we captured the natural range of variation. This information is useful for the interpretation of observed differences in D. magna performance between a GE plant and its non-GE comparator as it helps judging whether observed effects are of biological relevance. If differences between a GE and comparator line are observed and their biological relevance needs to be assessed in future risk assessments of GE maize, 1) the data on natural variation of the different parameters generated by previous studies can be informative (e.g. data from our study for maize fed D. magna); 2) for additional experiments the inclusion of multiple unrelated non-GE comparators should be considered; In addition, it should be taken into account that nutritional stress can affect the outcome of the study.
已经通过用含有苏云金芽孢杆菌（Bt）杀虫晶体蛋白的不同玉米材料喂养该物种来研究经基因工程（GE）改造的植物对水生大型蚤（Daphnia magna）的非靶标效应。这些研究的结果往往难以解释，因为仅比较了一个 GE 植物和一个相关的非 GE 对照。在这种情况下，Cry 蛋白的作用不能与植物背景作用区分开来，特别是当测试物种受到营养胁迫时。在本研究中，我们测试了来自五个不同非 GE 玉米系（包括 EXP 258，这是一个与 SmartStax Bt 玉米密切相关的育种种系）的三种不同玉米材料（即面粉、叶片和花粉）作为 D. magna 的唯一食物来源的适宜性。记录的参数包括存活率、亚致死终点，如体型大小、首次繁殖的蜕皮次数、首次繁殖时间、第一窝个体数、总窝数、总繁殖数、每窝平均繁殖数以及种群参数，如净生殖率 R、世代时间 T 和内禀增长率 r。结果表明，当仅用玉米材料喂养时，大型蚤可以存活、生长和繁殖，尽管其性能不如用藻类喂养时好，这表明存在营养胁迫。在不同的玉米系之间观察到大型蚤生活史和种群参数的巨大差异。我们的结果表明，营养胁迫和植物背景引起的混杂效应可能解释了先前关于 Bt 作物对 D. magna 影响的一些相互矛盾的结果。在我们的研究中，使用 95%置信区间捕获了五个玉米系的所有测量参数的平均值，从而捕获了自然变异范围。对于解释 GE 植物与其非 GE 对照之间的大型蚤性能差异，这些信息非常有用，因为它有助于判断观察到的影响是否具有生物学相关性。如果在 GE 玉米的未来风险评估中观察到 GE 植物与对照线之间的差异，并且需要评估其生物学相关性，则 1）之前研究生成的不同参数的自然变异数据可能具有信息性（例如，我们研究中有关用玉米喂养的大型蚤的数据）；2）对于额外的实验，应考虑包含多个不相关的非 GE 对照；此外，应考虑到营养胁迫会影响研究结果。
