Christen Verena, Grossar Daniela, Charrière Jean-Daniel, Eyer Michael, Jeker Lukas
University of Applied Sciences and Arts Northwestern Switzerland, School of Life Sciences, Muttenz, Switzerland.
Agroscope, Swiss Bee Research Center, Bern, Switzerland.
Front Insect Sci. 2021 Dec 10;1:765570. doi: 10.3389/finsc.2021.765570. eCollection 2021.
Neonicotinoids as thiamethoxam and thiacloprid are suspected to be implicated in the decline of honey bee populations. As nicotinic acetylcholine receptor agonists, they disturb acetylcholine receptor signaling in insects, leading to neurotoxicity and are therefore globally used as insecticides. Several behavioral studies have shown links between neonicotinoid exposure of bees and adverse effects on foraging activity, homing flight performance and reproduction, but the molecular aspects underlying these effects are not well-understood. In the last years, several studies through us and others showed the effects of exposure to neonicotinoids on gene expression in the brain of honey bees. Transcripts of acetylcholine receptors, hormonal regulation, stress markers, detoxification enzymes, immune system related genes and transcripts of the energy metabolism were altered after neonicotinoid exposure. To elucidate the link between homing flight performance and shifts in gene expression in the brain of honey bees after neonicotinoid exposure, we combined homing flight activity experiments applying RFID technology and gene expression analysis. We analyzed the expression of endocrine factors, stress genes, detoxification enzymes and genes linked to energy metabolism in forager bees after homing flight experiments. Three different experiments (experiment I: pilot study; experiment II: "worst-case" study and experiment III: laboratory study) were performed. In a pilot study, we wanted to investigate if we could see differences in gene expression between controls and exposed bees (experiment I). This first study was followed by a so-called "worst-case" study (experiment II), where we investigated mainly differences in the expression of transcripts linked to energy metabolism between fast and slow returning foragers. We found a correlation between homing flight duration and the expression of , one transcript linked to oxidative phosphorylation. In the third experiment (experiment III), foragers were exposed in the laboratory to 1 ng/bee thiamethoxam and 8 ng/bee thiacloprid followed by gene expression analysis without a subsequent flight experiment. We could partially confirm the induction of , which we detected in experiment II. In addition, we analyzed the effect of the feeding mode (group feeding vs. single bee feeding) on data scattering and demonstrated that single bee feeding is superior to group feeding as it significantly reduces variability in gene expression. Based on the data, we thus hypothesize that the disruption of energy metabolism may be one reason for a prolongation of homing flight duration in neonicotinoid treated bees.
噻虫嗪和噻虫啉等新烟碱类农药被怀疑与蜜蜂种群数量下降有关。作为烟碱型乙酰胆碱受体激动剂，它们会干扰昆虫体内的乙酰胆碱受体信号传导，导致神经毒性，因此在全球范围内被用作杀虫剂。多项行为学研究表明，蜜蜂接触新烟碱类农药与对觅食活动、归巢飞行性能和繁殖的不利影响之间存在关联，但这些影响背后的分子机制尚不清楚。在过去几年中，我们和其他一些研究表明了接触新烟碱类农药对蜜蜂大脑基因表达的影响。接触新烟碱类农药后，乙酰胆碱受体、激素调节、应激标志物、解毒酶、免疫系统相关基因以及能量代谢的转录本发生了改变。为了阐明新烟碱类农药暴露后蜜蜂归巢飞行性能与大脑基因表达变化之间的联系，我们将应用射频识别技术的归巢飞行活动实验与基因表达分析相结合。在归巢飞行实验后，我们分析了觅食蜜蜂体内内分泌因子、应激基因、解毒酶以及与能量代谢相关基因的表达情况。我们进行了三个不同的实验（实验I：初步研究；实验II：“最坏情况”研究；实验III：实验室研究）。在初步研究中，我们想探究是否能观察到对照蜜蜂和暴露蜜蜂之间的基因表达差异（实验I）。在第一项研究之后，我们进行了一项所谓的“最坏情况”研究（实验II），在该研究中，我们主要研究了快速和缓慢归巢的觅食蜜蜂之间与能量代谢相关转录本表达的差异。我们发现归巢飞行持续时间与一个与氧化磷酸化相关的转录本的表达之间存在相关性。在第三个实验（实验III）中，觅食蜜蜂在实验室中接触1纳克/只的噻虫嗪和8纳克/只的噻虫啉，随后进行基因表达分析，不进行后续飞行实验。我们可以部分证实我们在实验II中检测到的[转录本名称未明确]的诱导情况。此外，我们分析了喂养方式（群体喂养与单只蜜蜂喂养）对数据离散度的影响，并证明单只蜜蜂喂养优于群体喂养，因为它能显著降低基因表达的变异性。基于这些数据，我们因此推测能量代谢的紊乱可能是新烟碱类农药处理过的蜜蜂归巢飞行持续时间延长的一个原因。
