Forager bees (Apis mellifera) highly express immune and detoxification genes in tissues associated with nectar processing.

Rachel L Vannette,Brian R Johnson,Abbas Mohamed

doi:10.1038/srep16224

Rachel L Vannette, Brian R Johnson + Show 1 more

Open Access

https://doi.org/10.1038/srep16224

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Abstract

Pollinators, including honey bees, routinely encounter potentially harmful microorganisms and phytochemicals during foraging. However, the mechanisms by which honey bees manage these potential threats are poorly understood. In this study, we examine the expression of antimicrobial, immune and detoxification genes in Apis mellifera and compare between forager and nurse bees using tissue-specific RNA-seq and qPCR. Our analysis revealed extensive tissue-specific expression of antimicrobial, immune signaling, and detoxification genes. Variation in gene expression between worker stages was pronounced in the mandibular and hypopharyngeal gland (HPG), where foragers were enriched in transcripts that encode antimicrobial peptides (AMPs) and immune response. Additionally, forager HPGs and mandibular glands were enriched in transcripts encoding detoxification enzymes, including some associated with xenobiotic metabolism. Using qPCR on an independent dataset, we verified differential expression of three AMP and three P450 genes between foragers and nurses. High expression of AMP genes in nectar-processing tissues suggests that these peptides may contribute to antimicrobial properties of honey or to honey bee defense against environmentally-acquired microorganisms. Together, these results suggest that worker role and tissue-specific expression of AMPs, and immune and detoxification enzymes may contribute to defense against microorganisms and xenobiotic compounds acquired while foraging.

Highlights

Pollinators can maintain a relatively stable individual and hive microbiome[23,24] and examples of honey spoilage and chemical lethality to bees themselves from naturally-occurring compounds are rare[21], begging the question how honey bees can effectively cope with such microbial and chemical challenges[25]
Our analyses focus on the expression of genes involved in immunity, including those encoding antimicrobial peptides or proteins involved in immune signaling, and those involved in detoxification, including cytochrome P450 monooxygenases (Supplementary table S1 online)
The results presented here demonstrate that honey bee foragers exhibit greater expression of genes associated with immune response and detoxification activity than do nurse bees

Summary

Introduction

Pollinators can maintain a relatively stable individual and hive microbiome[23,24] and examples of honey spoilage and chemical lethality to bees themselves from naturally-occurring compounds are rare[21], begging the question how honey bees can effectively cope with such microbial and chemical challenges[25]. Honey bee tissues varied substantially in the abundance of particular transcripts, and of those encoding products with antimicrobial, immune signaling and detoxification functions The HPG was enriched in transcripts for antimicrobial peptides (AMPs) and honey-producing enzymes, while each tissue type was enriched with transcripts from different immune signaling and detoxification genes (Table 1).

Results

Conclusion