Forager Bees ‘Turn On’ Gene Expression to Protect Themselves from Microrganisms, Toxins

UC Davis Entomology & Nematology News   By Kathy Keatley Garvey   November 9, 2015

DAVIS--When honey bees shift from nurse bees to foragers, or from caring for the brood to foraging for nectar and pollen, the bees “turn on” gene expression with products that protect against  microorganisms and degrade toxins, three scientists at the University of California, Davis scientists have discovered.

The paper on bee immunity and toxin metabolism was published Nov. 9 in Scientific Reports, part of the Nature Publishing Group.

“First, the results suggest that forager bees may use antimicrobial peptides—short sequences of amino acids with general activity-- to reduce microbial growth in stored food resources,” said Rachel Vannette of the UC Davis Department of Entomology and Nematology. “This would be a largely unrecognized way that bees protect honey and potentially other stored resources from microbial spoilage. Second, this work shows that forager bees produce toxin-degrading enzymes in nectar-processing tissues.”

“This may allow forager bees to degrade many different kinds of compounds in nectar, before it is stored,” Vannette said. “Bees also vary in their ability to do this—foragers have a greater ability to degrade a variety of compounds than nurses. This may have implications for hive health and management.” 

The scientists found the change in nectar-processing tissues, but not in the gut.   The scientists surmised that the exposure to bacteria or yeasts in the environment may trigger this change, but they did not examine it in the study.

"Nice paper,” said Gene Robinson, director of the Institute for Genomic Biology and Swanlund Chair of Entomology, University of Illinois at Urbana-Champaign, who was not involved in the research. “It had been well known that the division of labor in a honey bee colony is supported by extensive differences in brain gene expression between bees that perform different jobs. This new research shows nicely that this genomic differentiation extends beyond the brain; different complements of active genes in a variety of tissues make each bee better suited for the job it needs to perform."

The journal article, titled “Forager Bees (Apis mellifera) Highly Express Immune and Detoxification Genes in Tissues Associated with Nectar Processing,” is the work of senior author/assistant professor Brian Johnson of the UC Davis Department of Entomology and Nematology, and co-authors Abbas Mohamed, graduate student researcher in the Johnson lab and a member of the Pharmacology and Toxicology Group, and assistant professor Vannette, who joined the UC Davis Department of Entomology this fall after serving a postdoctoral fellowship at Stanford University. At Stanford, Vannette examined the role of nectar chemistry in community assembly of yeasts and plant-pollinator interactions.

Johnson, whose research interests include animal behavior, evolution, theoretical biology and genomics, recently began long-term research on the honey bee immune system and the causes and consequences of economically important diseases /syndromes such as colony collapse disorder.

Mohamed, who has researched honey bees since 2011, is currently focusing on pesticide detoxification as a part of his master's degree research. "Honey bees have always fascinated me,” Mohamed said, “and there is nothing more exciting than to be at the edge of discovery, learning new things, and contributing to the field of our understanding of these amazing creatures.”

The team plans to follow up with functional assays to examine the potential of these gene products to (1) reduce microbial growth and (2) degrade a variety of natural and synthetic compounds.

The 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.”

Read at:


The COLOSS “BEEBOOK: standard methodologies for Apis mellifera research” edited by Vincent Dietemann of the Swiss Bee Research Centre, Agroscope Liebefeld-Posieux, Peter Neumann of the University of Bern, Switzerland, and Jamie Ellis of the University of Florida, USA, will be published both online in the Journal of Apicultural Research and as a hard copy book for use at the laboratory bench.

The COLOSS “BEEBOOK” is a unique venture that aims to standardise methods for studying the honey bee. It will be a practical manual, compiling standard methods in all fields of research on the honey bee, Apis mellifera, and become the definitive, but evolving, research manual, composed of 33 peer-reviewed chapters authored by more than 160 of the world’s leading honey bee experts. Chapters will describe methods for studying honey bee biology, methods for understanding honey bee pests and pathogens, and methods for breeding honey bees. The initial BEEBOOK project will be divided into three volumes: The COLOSS BEEBOOK, Volume I: Standard methods for Apis mellifera research; The COLOSS BEEBOOK, Volume II: Standard methods for Apis mellifera pest and pathogen research; and The COLOSS BEEBOOK, Volume III: Standar d methods for Apis mellifera product research.

The first group of papers belonging to both Volumes I and II are published today in a Special Issue of the Journal of Apicultural Research as Open Access papers, and the remainder will be published later in 2013, at the same time as the production of Volumes I and II as hard copy. Volume III will follow in 2014. These thirteen papers have been written by 98 authors representing 25 different countries, illustrating the unprecedented degree of international collaboration that the crisis in honey bees and the COLOSS network has engendered.

COLOSS COST Action Chair Prof. Peter Neumann says: “The editors and author team hope that the BEEBOOK will serve as a reference tool for honey bee and other researchers globally. We hope that the honey bee research community will embrace this tool and work to improve it. The online platform is open for everyone to use and further contribute to the development of our research field”.

FOR FURTHER INFORMATION PLEASE CONTACT Norman Carreck, Science Director, IBRA +44 (0)791 8670169 

The article “An update on the COLOSS network and the BEEBOOK: standard methodologies for Apis melliferaresearch” is available at:  The COLOSS BEEBOOK - Part 1 will be available at 

COLOSS is a network funded by the European Union COST Programme (Action FA0803) and the Ricola Foundation – Nature & Culture, which aims to explain and prevent massive honey bee colony losses. The network does not directly support science, but aims to coordinate international research activities across Europe and worldwide, promoting cooperative approaches and a research programme with a strong focus on the transfer of science into beekeeping practice. COLOSS has more than 300 members drawn from 60 countries worldwide.  It is chaired by Prof. Peter Neumann of the University of Bern, Switzerland. Website

The International Bee Research Association (“IBRA”) is the world's longest established apicultural research publishers and promotes the value of bees by providing information on bee science and beekeeping worldwide. IBRA publishes the peer reviewed scientific journal the Journal of Apicultural Research founded by IBRA in 1962.  It includes original research articles, theoretical papers; scientific notes and comments; together with authoritative reviews on scientific aspects of the biology, ecology, natural history, conservation and culture of all types of bee. IBRA publishes and sells books on bee science, bee conservation and beekeeping and also provides bee information services.  IBRA is a Registered Charity, and its Council of trustees boasts some of th e world’s leading bee scientists. Membership of IBRA costs just £33.00 annually.  Membership benefits include receipt of four quarterly issues of Bee World, our accessible and topical journal on latest bee research, news, reviews and other relevant information for the bee scientist, beekeeper, and anyone with an interest in bees., or

(The above is brought to us by CATCH THE BUZZ (Kim Flottum) Bee Culture, The Magazine of American Beekeeping, published by A.I. Root Company.)