I am interested in the structure, function, origin, and significance of naturally occurring compounds that mediate inter- and intraspecific interactions between organisms, especially economically important beneficial and pest insects. I use the tools of biology, molecular biology, genomics, biochemistry and chemistry to learn more within this interdisciplinary field.
I completed my BSc (Honours) in Chemistry at the University of Calgary, and my MSc and PhD in Chemistry at Simon Fraser University with Dr. Keith Slessor. During my PhD, I identified four new components of the queen honey bee pheromone, bringing the total number of synergistic components identified that elicit workers’ retinue attraction to the queen to nine. I then completed an NSERC postdoctoral fellowship with Drs. Claus Tittiger and Gary Blomquist at the University of Nevada, Reno, where I explored the functional genomics of pheromone biosynthesis in bark beetles.
I then worked with Dr. Jörg Bohlmann in the Michael Smith Laboratories at the University of British Columbia, where I explored how terpene synthases produce the chemical defences that conifers use to defend themselves against herbivores and pathogens. I also was co-investigator on a large-scale Genome BC/Genome AB-funded and Genome Canada-funded projects on the mountain pine beetle (Dendroctonus ponderoase), including sequencing the genome. We developed extensive genomic resources in the bark beetle and studied the molecular mechanisms of host colonization, such as pheromone biosynthesis and olfaction. As part of a US Department of Energy Joint Genome Institute Community Sequencing Program, we also sequenced ESTs from the southern pine beetle (Dendroctonus frontalis) using 454 sequencing technologies. I was later involved in the annotation of the white spruce genome sequence as part of the Genome Canada-funded SMarTForests Project.
I am currently working with Dr. Allison Kermode in the Department of Biological Sciences at Simon Fraser University. Here, I have begun studying seed development, dormancy, germination, seedling stress, and the inhibition of germination by seed resin vesicle contents in economically important conifers.
My CV can be found here: CV.pdf
Genomics-Enhanced Forecasting Tools to Secure Canada’s Near-Term Lignocellulosic Feedstock Supply for Bioenergy using the Mountain Pine Beetle System
‘Using genomics of the interacting bark beetles, fungal pathogens and host pine trees to improve forest ecological risk models’
My contribution as a co-investigator on this large-scale genomics project has been two-fold:
(1) Oversee the creation of genomics resources in the three interacting organisms (beetle, tree, and fungus).
(2) Investigate the processes of olfaction and pheromone biosynthesis in the mountain pine beetle, Dendroctonus ponderoase.
Research assistants Hannah Henderson and Maria Li work with me on this project.
Janice Cooke, University of Alberta
Jörg Bohlmann, University of British Columbia
Barry Cooke, Natural Resources Canada
Brian Aukema, Canadian Forest Service
Chris Keeling, Colette Breuil, and Richard Hamelin, University of British Columbia
Brent Murray and Dezene Huber, University of Northern British Columbia
David Coltman, Nadir Erbilgin, Maya Evenden, and Felix Sperling, University of Alberta
Marco Marra, Robert Holt, and Steven Jones, Michael Smith Genome Sciences Centre
Southern Pine Beetle
‘Development of a comprehensive EST library for the tree-killing southern pine beetle, Dendroctonus frontalis’
A 2009 US Department of Energy Joint Genome Institute Community Sequencing Program project.
This project has used 454 sequencing technologies to create an EST resource for this important bark beetle pest of Central American and Southeastern United State’s forests. This project will provide a comprehensive genetic resource for southern pine beetle researchers and will complement the genetic resources we are developing in the mountain pine beetle.
The EST data is available at NCBI SRA. Enjoy!
Scott Kelley, San Diego State University
Claus Tittiger, University of Nevada, Reno
Chris Keeling, Jörg Bohlmann, University of British Columbia
Dezene Huber, University of Northern British Columbia
Conifer Forest Health Genomics
My contributions to this project were:
(1) Identify and functionally characterize conifer terpene synthases of primary and secondary metabolism.
(2) Determine the roles of terpenoids in the defence of spruce against the white pine weevil, Pissodes strobi.
(3) Identify the specific amino acid residues of terpene synthases that determine product outcome in closely paralogous enzymes.
This research in Dr. Jörg Bohlmann’s lab was a team effort of scientists including me, research assistant Harpreet Sandhu, PhD candidate Jeanne Robert, and NSERC postdoctoral fellow Dawn Hall.
NSERC Postdoctoral Fellowship (Biochemistry and Molecular Biology, University of Nevada, Reno)
Gene expression in the pheromone-producing midgut of the pine engraver beetle (Ips pini (Say))
The pine engraver beetle is a significant pest of North American coniferous forests. The male is the pioneering sex and attracts mates to its nuptial chamber in the phloem of a host tree with a pheromone.
Upon feeding, and regulated by juvenile hormone III (JH), the pheromone component ipsdienol is biosynthesized de novo via the mevalonate pathway in the male midgut. Identifying and characterizing genes in the midgut that respond to JH treatment or feeding may yield the mode of JH action as well as targets for novel pest management strategies. cDNA microarrays were prepared representing 574 unique genes identified in an expressed sequence tag (EST) project of the midgut of JH-treated males. These microarrays were hybridized with fluorescently labeled cDNA from midgut tissue of fed, JH-treated, or control beetles. Replicated hybridizations have identified several genes that were significantly up or down regulated by JH or feeding. Time course experiments established ontogeny of response. Some of these were known mevalonate pathway genes, other known genes, and unknown genes. Characterization of some of these candidate genes have established their importance in pheromone biosynthesis.
PhD Thesis (Chemistry, Simon Fraser University)
Isolation and Identification of New Components of the Honey Bee (Apis mellifera L.) Queen Retinue Pheromone
Pheromones are chemicals used for communication between members of the same species. These semiochemicals can elicit either releaser or primer effects, changing the behavior or the physiology of the receiving organism respectively.
The honey bee queen produces pheromones that function in both releaser and primer roles such as attracting a retinue of workers around her, attracting drones on mating flights, preventing workers from reproducing at the individual (worker egg laying) and colony (swarming) level, and regulating several other aspects of colony functioning. The queen mandibular pheromone (QMP), consisting of five synergistic components, is the only pheromone chemically identified in the honey bee queen. However, this pheromone does not fully duplicate the pheromonal activity of a full queen extract. To identify the remaining unknown compounds for retinue attraction, honey bee colonies were selectively bred to have low response to synthetic QMP and high response to a queen extract in a laboratory retinue bioassay. Workers from these colonies then were used in the bioassay to guide the isolation and identification of the remaining active components in the queen extract. Four new compounds have been identified that accounted for the majority of the difference in attraction between synthetic QMP and queen extract. The queen therefore produces a synergistic pheromone blend of at least nine compounds for retinue attraction, the most complex pheromone blend known for a single behavior in any insect.
Analysis of the Mandibular Gland Components of Honey Bees
The mandibular gland is the source of a queen pheromone in Apis mellifera. This gland contains several functionalized carboxylic acids and several aromatic compounds. Although these compounds have not all been proven to act as a pheromone in Asian honey bee species, many of these compounds are common in the other species. I collaborated with biologists to investigate the differences in mandibular gland contents from the different honey bee species to ultimately understand the phylogeny of honey bee pheromones.
Preparative Chromatographic Separation of the Enantiomers of Pheromones
When chiral pheromones are first identified, the racemic form is usually synthesized (or purchased) to compare physical, chemical, and behavioral properties with the isolated pheromone. The next step is to investigate the stereochemistry. The chirality of a pheromone in an extract can be assessed through the use of chiral gas chromatography columns and other means. To test the biological activity of each enantiomer, they must be available in high chiral purity in quantities suitable for bioassay or field testing. This is usually done by chiral synthesis but this requires two, often lengthy, syntheses. Since the racemic form has already been made, and synthesis of the racemic form is usually much easier, the preparative separation of the enantiomers from the racemate can be a time and labor saving option. I investigated cellulose triacetate as a stationary phase for the preparative chiral separation of several pheromones that are very difficult to obtain chirally pure through chiral synthesis.
Funded by NSERC. Supervised by Dr. Keith N. Slessor (now retired–gone fishing).
MSc Thesis (Chemistry, Simon Fraser University)
Stable Carbon Isotope Ratio Measurements of the Carboxyl Carbons in Bone Collagen
These shifts in the isotopic ratio can be traced through the food chain. Crucial dietary information can be obtained by measuring the 13C/12C ratio of animal tissues such as bone collagen from archaeological samples. In my MSc thesis, I developed and tested a method to compare 13C/12C ratios between the total carbon in collagen and the carboxyl carbons in the amino acids of collagen hydrolysates. I hoped that differences in these ratios might provide additional dietary information and thus be another tool for nutritional analysis of archaeological samples. The carboxyl carbons were selectively removed by decarboxylation with ninhydrin (2,2-dihydroxy-1,3-indanedione). A survey of the differences in 13C/12C ratios between carboxyl and total carbons in bone collagen from several modern and archaeological samples revealed that the carboxyl carbons were usually isotopically heavier than total carbon. This difference in 13C/12C ratios ranged from -0.9 to 4.0 parts per thousand. Animals at higher trophic levels usually had smaller differences than lower animals. Humans had the largest range of differences, possibly due to a larger variability in their diets. An earlier study found the 13C/12C ratio of collagen in the extinct European cave bear (Ursus spelaeus) increased with age. My survey found even larger increases with age for the carboxyl carbons.