School of Environmental Sciences, University of Guelph, Guelph, Ontario, Canada.
PLoS One. 2020 Feb 20;15(2):e0229030. doi: 10.1371/journal.pone.0229030. eCollection 2020.
While many studies have examined the effects of neonicotinoid insecticides and the parasitic mite Varroa destructor on honey bees (Apis mellifera), more information on the combined effects of such stressors on gene expression, including neural related genes, and their impact on biological pathways is needed. This study analyzed the effects of field realistic concentrations of the neonicotinoid clothianidin on adult bees infested and not infested with V. destructor over 21 consecutive days and then determined bee survivorship, weight, deformed wing virus (DWV) levels and gene expression. V. destructor parasitism with or without clothianidin exposure was significantly associated with decreased survivorship, weight loss and higher DWV levels, while clothianidin exposure was only associated with higher levels of DWV. Expression analysis of the neural genes AmNlg-1, BlCh and AmAChE-2 showed that V. destructor caused a significant down-regulation of all of them, whereas clothianidin caused a significant down-regulation of only AmNrx-1 and BlCh. An interaction was only detected for AmNrx-1 expression. RNAseq analysis showed that clothianidin exposure resulted in 6.5 times more up-regulated differentially expressed genes (DEGs) than V. destructor alone and 123 times more than clothianidin combined with V. destructor. Similar results were obtained with down-regulated DEGs, except for a higher number of DEGs shared between V. destructor and the combined stressors. KEGG (Kyoto Encyclopedia of Genes and Genomes) biological pathway analysis of the DEGs showed that the stressor linked to the highest number of KEGG pathways was clothianidin, followed by V. destructor, and then considerably fewer number of KEGG pathways with the combined stressors. The reduced numbers of DEGs and KEGG pathways associated with the DEGs for the combined stressors compared to the stressors alone indicates that the interaction of the stressors is not additive or synergistic, but antagonistic. The possible implications of the antagonistic effect on the number of DEGs are discussed.
虽然许多研究都考察了新烟碱类杀虫剂和寄生螨瓦螨对蜜蜂（Apis mellifera）的影响，但需要更多关于这些压力源对基因表达（包括与神经相关的基因）的综合影响及其对生物途径的影响的信息。本研究分析了田间现实浓度的新烟碱类杀虫剂噻虫胺对 21 天连续感染和未感染瓦螨的成年蜜蜂的影响，然后确定了蜜蜂的存活率、体重、变形病毒（DWV）水平和基因表达。无论是否接触噻虫胺，瓦螨寄生都会显著降低蜜蜂的存活率、体重减轻和更高的 DWV 水平，而噻虫胺接触仅与更高的 DWV 水平相关。神经基因 AmNlg-1、BlCh 和 AmAChE-2 的表达分析表明，瓦螨导致它们全部显著下调，而噻虫胺仅导致 AmNrx-1 和 BlCh 显著下调。仅检测到 AmNrx-1 表达的相互作用。RNAseq 分析表明，与单独的瓦螨相比，噻虫胺暴露导致上调的差异表达基因（DEGs）增加了 6.5 倍，与噻虫胺和瓦螨的组合相比增加了 123 倍。下调的 DEGs 也得到了类似的结果，只是瓦螨和组合应激源之间共享的 DEGs 数量更多。DEGs 的 KEGG（京都基因与基因组百科全书）生物途径分析表明，与最多 KEGG 途径相关的应激源是噻虫胺，其次是瓦螨，然后是与组合应激源相关的数量相当少的 KEGG 途径。与单独的应激源相比，组合应激源的 DEGs 和 KEGG 途径的数量减少表明，应激源的相互作用不是加性或协同的，而是拮抗的。讨论了这种拮抗作用对 DEGs 数量的可能影响。
