The Impact of Nutrition on Within and Trans-generational Disease Resistance in the Cabbage Looper, Trichoplusia ni by Ikkei Shikano M.Sc., University of British Columbia, 2009 B.Sc., University of British Columbia, 2006 Thesis Submitted in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy in the Department of Biological Sciences Faculty of Science Ikkei Shikano 2014 SIMON FRASER UNIVERSITY Summer 2014 Approval Name: Ikkei Shikano Degree: Doctor of Philosophy Title: The Impact of Nutrition on Within and Trans-generational Disease Resistance in the Cabbage Looper, Trichoplusia ni Examining Committee: Chair: Dr. Ronald Ydenberg Professor Dr. Jenny Cory Senior Supervisor Professor Dr. Carl Lowenberger Supervisor Professor Dr. Gerhard Gries Supervisor Professor Dr. Tony Williams Internal Examiner Professor Department of Biological Sciences Dr. Emma Despland External Examiner Associate Professor Department of Biology Concordia University Date Defended/Approved: July 30, 2014 ii Partial Copyright Licence iii Abstract Parasites and pathogens are ubiquitous, and pose a threat to all living organisms. Investment in resistance mechanisms to fight parasite challenge can be costly, often resulting in trade-offs with other life-history traits. Host nutrition can alter the availability of resources to invest in resistance mechanisms and influence host-parasite interactions and their outcomes. I investigated the impact of nutrition on disease resistance in the cabbage looper, Trichoplusia ni. I assessed the role of dietary macronutrients on the expression of fitness costs exhibited by a T. ni strain that has evolved resistance to the bacterial pathogen, Bacillus thuringiensis (Bt). Reduced pupal weight and growth rate, which are fitness costs associated with Bt-resistance, resulted from reduced food intake rather than impaired macronutrient utilization. When given a choice, Bt-resistant T. ni self-composed a higher ratio of protein to carbohydrate (P:C ratio) than Bt-susceptible T. ni, allowing males to eliminate a fitness cost (reduced pupal weight), but not females. Next, I investigated the interaction between host nutrition and another key environmental factor, temperature, on the interaction between T. ni and two species of baculoviruses differing in host range (TnSNPV, narrow range; AcMNPV, broad range). Optimal performance of T. ni shifted to higher P:C ratios when challenged by either virus as survival increased with dietary protein content. This effect was strongly affected by temperature when challenged by AcMNPV but not TnSNPV. Virus performance was also differentially affected by the host’s environmental condition, such that AcMNPV had a broader peak of optimal performance (combined measure of host mortality and virus production) across environmental conditions than TnSNPV. Lastly, I examined the impact of nutritional stress on the ability of Bt-challenged T. ni to prime the immune system of their offspring. If parental T. ni experienced only nutritional stress or Bt- challenge, they transferred nutritional stress tolerance or immune priming to their offspring respectively. However, as surviving each stressor is costly, when experienced simultaneously a trade-off was observed where only immune priming was transferred. This study highlights the important influence of host nutrition on host resistance to pathogens, costs associated with resistance, and pathogen virulence and growth. Keywords: host-pathogen interaction; disease resistance; nutritional ecology; trans- generational immune priming; fitness costs iv Acknowledgements I have many people to thank for the completion of this thesis. My senior supervisor Dr. Jenny Cory for her patience, guidance and insightful comments that have helped me build my critical thinking, knowledge and confidence as a researcher. I would also like to thank my committee members Dr. Carl Lowenberger and Dr. Gerhard Gries for their valuable insights on my project. Thank you to all current and former post-docs, graduate students and lab technicians in the Cory Lab for their input on my research designs, results and presentations. I appreciated our lively scientific and non-scientific discussions. I could not have completed this project and other side-projects without the help of numerous undergraduate assistants and volunteers. I would especially like to thank Kevin Hua for his long-term volunteer commitment and Olivia Halpert-Scanderbeg and Miranda Oak for their hard work in helping me complete a part of this project. I thank my former mentors, Dr. Murray Isman, Dr. Yasmin Akhtar and Dr. Judith Myers from my time as an undergraduate and Master’s student. They have given me the foundation and passion to pursue science as a career. Thanks to the Natural Sciences and Engineering Research Council of Canada, Simon Fraser University, Government of British Columbia, Mutual Fire Insurance Company and Sulzer Pumps Inc. for funding. Last but not least, I would like to thank my lovely wife Ryoko for always encouraging me to pursue my interests. Thank you for labeling thousands of plastic cups for experiments that did not work, with minimal complaining! v Table of Contents Approval .............................................................................................................................ii Partial Copyright Licence .................................................................................................. iii Abstract .............................................................................................................................iv Acknowledgements ........................................................................................................... v Table of Contents ..............................................................................................................vi List of Tables .....................................................................................................................ix List of Figures.................................................................................................................... x Chapter 1. Introduction ............................................................................................... 1 1.1. General overview of resistance mechanisms ........................................................... 3 1.2. Primed resistance..................................................................................................... 5 1.3. Costs associated with resistance ............................................................................. 6 1.4. Nutrient availability and disease resistance ............................................................. 7 1.4.1. Starvation and food limitation effects on resistance .................................... 7 1.4.2. Host plant quality effects on resistance ...................................................... 8 1.4.3. Nutrient effects on resistance ..................................................................... 9 1.4.4. Trans-generational effects of nutrients on offspring resistance ................ 11 1.5. Host nutrition and parasite fitness .......................................................................... 12 1.6. The study system ................................................................................................... 12 1.6.1. Pathogens: NPVs ...................................................................................... 12 1.6.2. Pathogens: Bt ........................................................................................... 14 1.6.3. Insect ........................................................................................................ 16 1.7. Thesis chapters ...................................................................................................... 16 1.8. References ............................................................................................................. 19 1.9. Connecting statement ............................................................................................ 33 Chapter 2. Genetic resistance to Bacillus thuringiensis alters feeding behaviour in the cabbage looper, Trichoplusia ni ............................... 34 2.1. Abstract .................................................................................................................. 34 2.2. Introduction ............................................................................................................ 35 2.3. Materials and methods ........................................................................................... 36 2.3.1. Study animals ........................................................................................... 36 2.3.2. Artificial diets ............................................................................................. 37 2.3.3. Choice experiments .................................................................................. 37 2.3.4. Statistical analyses ................................................................................... 38 2.4. Results ................................................................................................................... 38 2.5. Discussion .............................................................................................................. 44 2.6. Acknowledgements ................................................................................................ 46 2.7. References ............................................................................................................