Data from: Inducible versus constitutive social immunity: examining effects of colony infection on glucose oxidase and defensin-1 production in honeybees

Honeybees use a variety of defence mechanisms to reduce disease infection and spread throughout the colony. Many of these defences rely on the collective action of multiple individuals to prevent, reduce or eradicate pathogens—often referred to as ‘social immunity’. Glucose oxidase (GOX) and some antimicrobial peptides (e.g. defensin-1 or Def1) are secreted by the hypopharyngeal gland of adult bees on larval food for their antiseptic properties. Because workers secrete these compounds to protect larvae, they have been used as ‘biomarkers’ for social immunity. The aim of this study was to investigate if GOX and Def1 are induced after pathogen exposure to determine whether its production by workers is the result of a collective effort to protect the brood and colony in response to a pathogen challenge. Specifically, we quantified GOX and Def1 in honeybee adults before and after colony-level bacterial infection by American foulbrood ((AFB), Paenibacillus larvae). Overall, our results indicate that levels of GOX and Def1 are not induced in response to pathogenic infections. We therefore conclude that GOX and Def1 are highly constitutive and co-opted as mechanisms of social immunity, and these factors should be considered when investigating immunity at the individual and colony level in social insects.

蜜蜂依托多种防御机制以降低病害感染风险并遏制其在蜂群内的传播。其中多数防御依赖多个个体的协同行为来阻止、减轻或根除病原体，这类防御通常被称为“社会免疫（social immunity）”。葡萄糖氧化酶（Glucose oxidase, GOX）与部分抗菌肽（如防御素-1，即Def1）由成年工蜂的咽下腺分泌至幼虫食物中，凭借其防腐特性发挥作用。由于工蜂分泌此类物质以保护幼虫，它们已被用作社会免疫的“生物标志物（biomarker）”。本研究旨在探究病原体暴露后GOX与Def1的表达是否被诱导，以此明确工蜂对二者的合成是否为应对病原体侵染时，为保护蜂卵、幼虫及整个蜂群而采取的协同防御行为的结果。具体而言，我们对蜂群经美洲幼虫腐臭病（American foulbrood, AFB，病原菌为Paenibacillus larvae）感染前后的成年蜜蜂体内GOX与Def1水平进行了定量检测。整体而言，研究结果显示，GOX与Def1的水平并未因致病性感染而被诱导上调。据此我们得出结论：GOX与Def1属于高度组成型表达的物质，且被招募为社会免疫的作用机制；在研究社会性昆虫的个体与群体免疫时，应将这两类因子纳入考量范畴。