The Pennsylvania State University The Graduate School Entomology Department HONEY BEES AND INTESTINAL DISEASE: MOLECULAR, PHYSIOLOGICAL AND BEHAVIORAL RESPONSES OF HONEY BEES (APIS MELLIFERA) TO INFECTION WITH MICROSPORIDIAN PARASITES A Dissertation in Entomology by Holly L. Holt 2015 Holly L. Holt Submitted in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy August 2015 The dissertation of Holly L. Holt was reviewed and approved* by the following: Christina Grozinger Professor of Entomology, Director of The Center for Pollinator Research Dissertation Advisor Chair of Committee Diana Cox-Foster Professor of Entomology Kelli Hoover Professor of Entomology James H. Marden Professor of Biology Gary W. Felton Professor of Entomology Head of the Department of Entomology *Signatures are on file in the Graduate School iii ABSTRACT Pollinators are integral to modern agricultural productivity and the continued survival and vitality of natural ecosystems. However, recent declines in pollinator populations and species diversity threaten both food security and the architecture of natural habitats. Due to their vital role in agriculture, honey bees (Apis mellifera) have served as a model organism for investigating the alarming and widespread diminution of pollinator populations. Indeed, surveys from both North America and Europe report large annual colony losses. Parasites along with chemical exposure, poor nutrition, climate change and habitat destruction are frequently cited as leading causes of colony loss. Honey bee colonies are assaulted by a battery of bacterial, fungal and viral pathogens in addition to other parasitic arthropods including mites and beetles. Novel, cost- effective disease management practices are desperately needed to preserve colony health. Basic studies investigating honey bee immunity and disease pathology lay the groundwork for developing efficacious diagnostic tools and treatments. Here, we present a series of studies characterizing honey bee immunity and the molecular, physiological and behavioral responses of honey bees to two important fungal pathogens, Nosema apis and Nosema ceranae. Chapter 1 reviews the current state of research on these prevalent and destructive disease agents and highlights future studies that are needed to develop effective management practices. Chapter 2 investigates worker honey bee genomic responses to general immune stimulation. Findings from these experiments provide a contextual framework for Chapter 3’s studies which characterize worker honey bee genomic responses to infection with Nosema parasites and offer a molecular model for explaining previously documented disease symptoms. Chapter 4 investigates drone (male) honey bee molecular, physiological and behavioral responses to Nosema infection and underscores potential caste-specific responses to infection that have larger implications for colony fitness. Finally, Chapter 5 summarizes novel findings from this dissertation, integrates results with current scientific literature and discusses the future of Nosema management. iv TABLE OF CONTENTS List of Figures ......................................................................................................................... viii List of Tables ........................................................................................................................... x Acknowledgements .................................................................................................................. xi Chapter 1 Towards an integrated pest management (IPM) approach for Nosema parasites in honey bee (Apis mellifera) colonies ............................................................................. 1 Abstract ............................................................................................................................ 1 1.0 Introduction ................................................................................................................ 1 2.0 Nosema parasites and noseomosis ............................................................................. 2 2.1 Nosema apis and Nosema ceranae are microsporidian parasites of honey bees ................................................................................................................... 2 2.2 Nosema spp. global distribution and factors affecting virulence in managed honey bee colonies ........................................................................................... 3 2.3 Nosema spp. global distribution in native pollinator populations: ..................... 5 2.4 Nosema spp. pathology: consequences for individual workers and honey bee colonies ...................................................................................................... 5 2.5 Nosema spp. pathology: consequences for adult queens and drones and immature castes ................................................................................................ 7 2.6 Nosema virulence factors and host defense mechanisms ................................... 7 3.0 Methods for diagnosing Nosema infections in colonies ............................................. 9 3.1 Light microscopy................................................................................................ 9 3.2 Molecular techniques ......................................................................................... 10 3.3 ELISA (Enzyme-Linked Immunosorbent Assay) test ........................................ 11 3.4 Measuring acoustic or odor signatures of colony stress ..................................... 12 4.0 Challenges with establishing treatment thresholds .................................................... 12 4.1 Sampling colonies for Nosema infection ............................................................ 12 4.2 Setting EILs (Economic Injury Levels) .............................................................. 13 5.0 Currently available and potential future Nosema treatments ..................................... 14 5.1 Chemical treatments ........................................................................................... 14 5.2 Hive sterilization methods .................................................................................. 18 5.3 Colony management practices............................................................................ 18 v 6.0 Summary and future directions .................................................................................. 21 Box 1: Integrated Pest Management ................................................................................ 22 Box 2: Microsporidia ....................................................................................................... 23 Box 3: Honeybee colony demographics and division of labor (see [167] for a review) ...................................................................................................................... 23 7.0 Acknowledgements .................................................................................................... 24 Chapter 2 Effects of immunostimulation on genome-wide gene expression in honey bee workers (Apis mellifera) ................................................................................................... 25 Abstract ............................................................................................................................ 25 1.0 Introduction ................................................................................................................ 26 2.0 Methods ...................................................................................................................... 27 2.1 Honey bee stocks ................................................................................................ 27 2.2 Honey bee rearing .............................................................................................. 28 2.3 Experimental treatment ...................................................................................... 28 2.4 Microarrays ........................................................................................................ 28 2.5 Analysis of Gene Expression ............................................................................. 29 2.6 Validation of candidate gene expression patterns using quantitative real- time PCR. ......................................................................................................... 30 3.0 Results ........................................................................................................................ 32 3.1 Global gene expression responses to immunostimulation .................................. 32 3.2 Effects of individual immune elicitors on gene expression ................................ 34 3.3 Functional analysis of regulated genes ............................................................... 35 3.4 Comparisons of gene expression patterns with previous studies ....................... 36 3.5 Quantitative real-time PCR validation of expression of candidate genes .......... 37 4.0 Discussion .................................................................................................................. 38 5.0 Conclusions ................................................................................................................ 40 6.0 Acknowledgements .................................................................................................... 41 Chapter 3 Chronic parasitization by Nosema microsporidia causes global expression