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侵染并阻止其在蜂群内扩散。其中多数防御依赖多只个体的协同行为以防控、减轻或清除病原体，这类防御通常被称为‘社会免疫（social immunity）’。成年蜜蜂的咽下腺会分泌葡萄糖氧化酶（Glucose oxidase, GOX）与部分抗菌肽（如防御素-1，即Def1）至幼虫饲料中，以发挥防腐功效。由于工蜂分泌此类物质以保护幼虫，这些物质已被用作社会免疫的‘生物标志物（biomarker）’。本研究旨在探究GOX与Def1在病原体暴露后是否会被诱导表达，以明确工蜂对二者的合成是否为响应病原侵染、协同保护蜂卵幼虫与蜂群的结果。具体而言，我们分别在蜂群遭受美洲幼虫腐臭病（American foulbrood, AFB，即幼虫芽孢杆菌Paenibacillus larvae）细菌性侵染的前后，对成年蜜蜂体内的GOX与Def1水平进行了定量检测。整体而言，实验结果显示GOX与Def1的水平并未因病原侵染而被诱导上调。据此我们得出结论：GOX与Def1属于高度组成型表达的物质，被纳入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，应将此类因子纳入考量范畴。