Immune gene expression in developing honey bees (Apis mellifera L.) simultaneously exposed to imidacloprid and Varroa destructor in laboratory conditions

The impact of widespread pesticide use in agriculture has been a major concern to the beekeeping industry. Accumulating evidence suggests that pesticides have a negative impact on honey bees. Additionally, honey bees exposed to different stressors, such as parasites and the pathogens they vector, may further affect their health. The aim of this study was to investigate the combined or sole effect of two stressors on developing honey bees under laboratory conditions where larvae were per os treated with realistic field doses of imidacloprid and later infested with Varroa destructor. Here, we present a gene expression profile of 15 immune-related genes in different honey bee development stages (white-eyed pupae, brown-eyed pupae, and emerged honey bees). Our results show that pesticide consumed in the larval stage lead to a decrease in immune response of bees in early development stages (white- and brown-eyed pupae) and later to an increase in honey bee immune response, and thus honey bee health may be challenged. The gene expression patterns of Varroa infested honey bees changed during development with the number of significantly differentially expressed genes increasing from white-eyed pupae to newly emerged honey bees. The effect of both stressors has a significant effect on antimicrobial peptides and genes involved in defense (apidaecin, hymenoptaecin, defensin-1, lysozyme-2, and PPO) in different developmental stages. All tested honey bees exposed to Varroa had significantly elevated DWV loads. Overall, our data showed changes in immune-related gene expression of three honey bee development stages, exposed to each of two stressors alone or combined, which varies depending on the developmental stage.

农业中农药的广泛使用所产生的影响，一直是养蜂业的重大关切议题。日益积累的研究证据表明，农药会对蜜蜂产生负面影响。此外，暴露于各类胁迫因子（如寄生虫及其携带的病原体）的蜜蜂，其健康状况可能会进一步受损。本研究旨在探究两种胁迫因子在实验室条件下对发育中蜜蜂的单独及联合作用：试验组幼虫经口暴露于符合田间实际使用剂量的吡虫啉（imidacloprid），随后侵染狄斯瓦螨（Varroa destructor）。本研究测定了蜜蜂不同发育阶段（白眼蛹、棕眼蛹及羽化出房成蜂）中15个免疫相关基因的基因表达谱。研究结果显示，幼虫阶段摄入的农药会导致蜜蜂在发育早期（白眼蛹和棕眼蛹阶段）的免疫应答水平下降，而在发育后期则会提升蜜蜂的免疫应答能力，进而可能对蜜蜂健康构成威胁。感染狄斯瓦螨的蜜蜂，其基因表达模式随发育进程发生改变：显著差异表达基因的数量从白眼蛹阶段到新羽化成蜂阶段逐渐增加。两种胁迫因子的共同作用，会对不同发育阶段蜜蜂的抗菌肽及防御相关基因（蜂肽素（apidaecin）、膜翅肽（hymenoptaecin）、防御素-1（defensin-1）、溶菌酶-2（lysozyme-2）及酚氧化酶原（PPO））产生显著影响。所有暴露于狄斯瓦螨的试验蜜蜂，其体内翼状畸形病毒（DWV）载量均显著升高。综上，本研究数据显示，在三个蜜蜂发育阶段中，单独或联合暴露于两种胁迫因子的蜜蜂，其免疫相关基因的表达均发生改变，且这种改变因发育阶段不同而存在差异。