PDF(Pubmed)
Abstract：
Over the last two decades, honey bees (Apis mellifera) have suffered high rates of colony losses that have been attributed to a variety of factors, chief among which are viral pathogens, such as deformed wing virus (DWV), whose virulence has increased because of vector-based transmission by the invasive, ectoparasitic varroa mite (Varroa destructor). A shift in the experimental mode of transmission of the black queen cell virus (BQCV) and sacbrood virus (SBV) from fecal/food-oral (direct horizontal) to vector-mediated (indirect horizontal) transmission also results in high virulence and viral titers in pupal and adult honey bees. Agricultural pesticides represent another factor that acts independently or in interaction with pathogens, and they are also thought to cause colony loss. Understanding the molecular mechanisms underlying the higher virulence following a vector-based mode of transmission provides deeper insight into honey bee colony losses, as does determining whether or not host-pathogen interactions are modulated by exposure to pesticides.
Through an experimental design with controlled laboratory, we investigated the effects of the modes of transmission of BQCV and SBV (feeding vs. vector-mediated via injection) alone or in combination with chronic exposure to sublethal and field-realistic concentrations of flupyradifurone (FPF), a novel agricultural insecticide, on honey bee survival and transcription responses by using high-throughput RNA sequencing (RNA-seq) analysis.
Co-exposure to viruses via feeding (VF) or injection (VI) and FPF insecticide had no statistically significant interactive effect on their survival compared to, respectively, VF or VI treatments alone. Transcriptomic analysis revealed a distinct difference in the gene expression profiles of bees inoculated with viruses via injection (VI) and exposed to FPF insecticide (VI+FPF). The number of differentially expressed genes (DEGs) at log2 (fold-change) > 2.0 in VI bees (136 genes) or/and VI+FPF insecticide (282 genes) was very high compared to that of VF bees (8 genes) or the VF+FPF insecticide treatment (15 genes). Of these DEGs, the expression in VI and VI+FPF bees of some immune-related genes, such as those for antimicrobial peptides, Ago2, and Dicer, was induced. In short, several genes encoding odorant binding proteins, chemosensory proteins, odor receptors, honey bee venom peptides, and vitellogenin were downregulated in VI and VI+FPF bees.
Given the importance of these suppressed genes in honey bees\' innate immunity, eicosanoid biosynthesis, and olfactory associative function, their inhibition because of the change in the mode of infection with BQCV and SBV to vector-mediated transmission (injection into haemocoel) could explain the high virulence observed in these viruses when they were experimentally injected into hosts. These changes may help explain why other viruses, such as DWV, represent such a threat to colony survival when transmitted by varroa mites.
Through an experimental design with controlled laboratory, we investigated the effects of the modes of transmission of BQCV and SBV (feeding vs. vector-mediated via injection) alone or in combination with chronic exposure to sublethal and field-realistic concentrations of flupyradifurone (FPF), a novel agricultural insecticide, on honey bee survival and transcription responses by using high-throughput RNA sequencing (RNA-seq) analysis.
Co-exposure to viruses via feeding (VF) or injection (VI) and FPF insecticide had no statistically significant interactive effect on their survival compared to, respectively, VF or VI treatments alone. Transcriptomic analysis revealed a distinct difference in the gene expression profiles of bees inoculated with viruses via injection (VI) and exposed to FPF insecticide (VI+FPF). The number of differentially expressed genes (DEGs) at log2 (fold-change) > 2.0 in VI bees (136 genes) or/and VI+FPF insecticide (282 genes) was very high compared to that of VF bees (8 genes) or the VF+FPF insecticide treatment (15 genes). Of these DEGs, the expression in VI and VI+FPF bees of some immune-related genes, such as those for antimicrobial peptides, Ago2, and Dicer, was induced. In short, several genes encoding odorant binding proteins, chemosensory proteins, odor receptors, honey bee venom peptides, and vitellogenin were downregulated in VI and VI+FPF bees.
Given the importance of these suppressed genes in honey bees\' innate immunity, eicosanoid biosynthesis, and olfactory associative function, their inhibition because of the change in the mode of infection with BQCV and SBV to vector-mediated transmission (injection into haemocoel) could explain the high virulence observed in these viruses when they were experimentally injected into hosts. These changes may help explain why other viruses, such as DWV, represent such a threat to colony survival when transmitted by varroa mites.
摘要：
背景：在过去的二十年里，蜜蜂（Apismellifera）遭受了很高的群体损失率，这归因于多种因素，其中主要是病毒病原体，例如畸形的机翼病毒(DWV)，由于侵入性的基于媒介的传播，其毒力增加了，外寄生虫瓦螨（Varroadestructor）。黑皇后细胞病毒（BQCV）和囊状病毒（SBV）的实验传播方式从粪便/食物口服（直接水平）到载体介导的（间接水平）传播的转变也导致高毒力和病毒滴度在p和成年蜜蜂中。农业农药代表了另一个独立或与病原体相互作用的因素，它们也被认为会导致殖民地损失。了解基于媒介的传播方式后更高毒力的分子机制，可以更深入地了解蜜蜂群体的损失，确定是否通过暴露于农药来调节宿主与病原体的相互作用。
方法：通过具有受控实验室的实验设计，我们研究了BQCV和SBV传播方式的影响(进料与通过注射介导的载体）单独或与慢性暴露于亚致死和现场现实浓度的氟吡唑啉酮（FPF）联合使用，一种新型的农业杀虫剂，通过使用高通量RNA测序（RNA-seq）分析来研究蜜蜂的存活和转录反应。
结果：通过摄食（VF）或注射（VI）与FPF杀虫剂共同接触病毒对其存活率没有统计学意义的交互作用，分别,单独VF或VI治疗。转录组学分析显示，通过注射（VI）接种病毒并暴露于FPF杀虫剂（VIFPF）的蜜蜂的基因表达谱存在明显差异。与VF蜜蜂（8个基因）或VFFPF杀虫剂处理（15个基因）相比，VI蜜蜂（136个基因）或/和VIFPF杀虫剂（282个基因）中log2（倍数变化）>2.0的差异表达基因（DEGs）的数量非常高。在这些DEG中,一些免疫相关基因在VI和VI+FPF蜜蜂中的表达，比如抗菌肽，Ago2和Dicer,是诱导的。总之,几个编码气味结合蛋白的基因，化学感觉蛋白，气味受体,蜂蜜蜂毒肽，在VI和VIFPF蜜蜂中，卵黄蛋白原表达下调。
结论：鉴于这些抑制基因在蜜蜂先天免疫中的重要性，类花生酸生物合成，和嗅觉关联功能，由于BQCV和SBV的感染方式改变为载体介导的传播(注射入血液中),它们的抑制作用可以解释实验注射入宿主时在这些病毒中观察到的高毒力.这些变化可能有助于解释为什么其他病毒，例如DWV，当由瓦罗螨传播时，代表了对菌落生存的威胁。
方法：通过具有受控实验室的实验设计，我们研究了BQCV和SBV传播方式的影响(进料与通过注射介导的载体）单独或与慢性暴露于亚致死和现场现实浓度的氟吡唑啉酮（FPF）联合使用，一种新型的农业杀虫剂，通过使用高通量RNA测序（RNA-seq）分析来研究蜜蜂的存活和转录反应。
结果：通过摄食（VF）或注射（VI）与FPF杀虫剂共同接触病毒对其存活率没有统计学意义的交互作用，分别,单独VF或VI治疗。转录组学分析显示，通过注射（VI）接种病毒并暴露于FPF杀虫剂（VIFPF）的蜜蜂的基因表达谱存在明显差异。与VF蜜蜂（8个基因）或VFFPF杀虫剂处理（15个基因）相比，VI蜜蜂（136个基因）或/和VIFPF杀虫剂（282个基因）中log2（倍数变化）>2.0的差异表达基因（DEGs）的数量非常高。在这些DEG中,一些免疫相关基因在VI和VI+FPF蜜蜂中的表达，比如抗菌肽，Ago2和Dicer,是诱导的。总之,几个编码气味结合蛋白的基因，化学感觉蛋白，气味受体,蜂蜜蜂毒肽，在VI和VIFPF蜜蜂中，卵黄蛋白原表达下调。
结论：鉴于这些抑制基因在蜜蜂先天免疫中的重要性，类花生酸生物合成，和嗅觉关联功能，由于BQCV和SBV的感染方式改变为载体介导的传播(注射入血液中),它们的抑制作用可以解释实验注射入宿主时在这些病毒中观察到的高毒力.这些变化可能有助于解释为什么其他病毒，例如DWV，当由瓦罗螨传播时，代表了对菌落生存的威胁。
