Honours Theses/Papers

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A trait-based assessment of the functional diversity of marine Cetacea in the Canadian Offshore Pacific Bioregion
(2025) Tuck, Matthew
The identification of biodiversity hotspots is a critical step in the protection and conservation of wildlife, and the ecosystems they depend upon. Recently, the identification of numerous highly diverse benthic seafloor and seamount habitats in the Canadian Offshore Pacific Bioregion (OPB) has prompted the establishment of large marine protected areas (MPAs) which target the protection of these sensitive benthic habitats. This region has high productivity due to eddy associated upwelling of nutrients, and contains numerous unique environments, including the continental slope, cold water seamounts, hydrothermal vents, and the open ocean. Elevated productivity supports a number of Cetacea species, which take advantage of seasonal windows of productivity. Cetaceans provide ecological functions related to nutrient transfer (e.g., the whale pump), food web processes (e.g, suppression of lower trophic levels), and the creation of unique seafloor habitats (i.e., whale falls). Despite the functional importance of these species, present conservation measures in the OPB and its associated MPAs do not legislate protections targeting the surface waters Cetacea species depend on. Here, I assess whether the OPB hosts a functionally diverse subset of the global marine Cetacea species pool through comparative analyses based on the global functional space of Cetacea spp., using seven traits related to species roles in food web processes and nutrient cycling. I also identify unique features of the species found in the OPB by comparing their trait distribution to the global Cetacea species pool. The OPB hosts 28% of the known marine Cetacea species but encompasses 70% of the global marine cetacean functional space. The functional dispersion and functional redundancy of the OPB mirrors values obtained from randomly subsampling the global species pool, indicating that the region is a representative sample of functional diversity present in the global species pool. Species using the OPB are distinguished by increased body sizes, likely due to the increased richness of large-bodied, baleen feeding Mysticeti species. The functional roles of large bodied species are fundamental for ecosystem health and stability, but are being eroded around the world as human activities continue to down-size the populations of the largest megafauna on Earth. Thus, the OPB is critical for protecting a high proportion of the global cetacean functional diversity, and the ecological roles of large cetaceans.
The contribution of NMDA receptors to contrast coding in ON retinal ganglion cells of Mus musculus
(2024) Westby, Tamatea
The retina encodes contrast (the difference in light intensity between an object and its background) using a complex network of neurons that end in ganglion cells (GCs) which transmit visual signals to the brain. GCs express both AMPA and NMDA type glutamate receptors, with NMDA receptors (NMDARs) having high glutamate affinity and variable localization patterns. Previous studies in guinea pig retinas found no NMDAR contribution to contrast coding in ON-∝ GCs but found that these receptors were expressed in mice ON-GCs. My study investigated the contribution of NMDARs to contrast coding in mouse ON-GCs. I used whole-cell voltage clamp electrophysiology in ON-GCs from Mus musculus retinas and recorded light-evoked responses to spots of varying contrast. I then determined receptor-specific contributions to the recorded responses using a deconvolution technique which avoided the potential confounding effects of using pharmacology. I first investigated whether NMDARs contribute to low contrast responses and then examined how their conductance changes with increasing contrast. The results revealed a significant NMDAR component to low contrast responses that scaled with increasing contrast. These findings provide new insight into contrast coding mechanisms in the retina, suggesting that NMDARs play a key role in shaping ON-GC responses.
Quantitative analysis of 3D heterochromatin structures within and between neuronal cell types
(2025) Smith, Rory
Heterochromatin organization within neuronal nuclei plays a critical role in maintaining genomic stability and regulating gene expression, yet its 3D morphological variability between neuron types remains poorly understood. Using confocal microscopy, we quantitatively analyzed heterochromatin 3D structures within neuronal nuclei. Existing methods in the literature were re-created to measure the distribution of nuclear intensity into predefined classes, as well as basic morphological features of the foci (volume, eccentricity, etc.). However, these morphological descriptors impose rigid, preconceived geometric assumptions that do not consider 3D spatial positioning. We attempt to address these limitations with a novel computational method that directly assays both spatial and morphological "similarity" of heterochromatin formations in nuclei. This approach was applied to a range of neuron types to assess variation within and between groups. Our results demonstrate significant differences between spatial heterochromatin foci positioning between neural types. If coupled with immunohistochemistry and increased replicates, we conclude with a demonstration of how this analysis could be applied to effectively study single-genotype differences in heterochromatin formation. This methodology offers a generalizable framework for studying morphological changes in other genotypes and nuclear protein disorders, which is of interest to various neurodevelopmental disorders.
Characterizing the impact of oocyte nutrient-sensitive genes on reproductive aging in Caenorhabditis elegans
(2025) Rossander, Emma
Reproductive aging is the gradual decline in reproductive function over time, encompassing reductions in fertility, hormonal changes, and diminished germ cell quality. This process is highly sensitive to nutrient conditions, as sufficient energy availability is essential for maintaining reproductive function. However, nutrient surplus may accelerate aging and impair fertility. Prior studies have demonstrated that Caenorhabditis elegans (C. elegans) exposed to a high-glucose diet exhibit reduced reproductive capacity and compromised oocyte quality. Poor oocyte quality is a well-documented contributor to reproductive dysfunction in both C. elegans and humans, underscoring the importance of understanding the molecular mechanisms that influence reproductive health under obesogenic diets. Genes whose transcription is regulated in a nutrient-sensitive manner play a critical role in mediating the relationship between diet and reproductive function. This study aimed to determine the impact of two such genes, icmt-1 and psme-4, on the reproductive capacity of C. elegans by using RNAi-mediated knockdown. C. elegans were exposed to lifelong RNAi and subject to elevated glucose exposure (20 mM glucose) starting at the fourth larval stage to coincide with establishment of the reproductive system. To assess the reproductive capacity in aging worms, C. elegans were mated on day five (D5) of adulthood, and their reproductive success was evaluated based on progeny production. Additionally, D5 oocytes were imaged using DIC imaging to assess morphological changes and overall oocyte quality in response to gene knockdown and high-glucose exposure. This study found that the RNAi knockdown of icmt-1 significantly reduced reproductive success in aging C. elegans, potentially due to systemic effects rather than direct impact on oocyte quality. Since icmt-1 regulates Ras protien localization and apoptotic pathways, its knockdown may cause widespread cellular stress and metabolic disruptions that impair reproduction. Conversely, psme-4 knockdown significantly improved age-related reproductive success and oocyte quality under glucose-enriched conditions, suggesting that reducing proteasomal activity may mitigate glucose-induced reproductive decline. psme-4 knockdown did not significantly affect reproductive capacity under normal dietary conditions, indicating that its glucose-induced upregulation may play a role in the reproductive defects observed under high-glucose conditions. These findings suggest that icmt-1 and psme-4 influence reproductive responses to dietary glucose, offering insight into the genetic basis of diet-induced infertility.
Analysis of synaptic plasticity events concerning the endocannabinoid system in the young adolescent (YA) rat media perforant pathway (MPP) following repetitive mild traumatic brain injury (r-mTBI)
(2025) Zejnulahovic, Emir
Traumatic brain injury (TBI) is a widespread health issue, with mild TBIs (mTBI) making up to 85% of cases, often underdiagnosed due to subtle symptoms. Young adolescents are most at risk for repetitive mTBI (r-mTBI), which compounds mTBI symptoms and outcomes. These injuries can impair synaptic plasticity, including short-term potentiation (STP) and long-term potentiation (LTP), both crucial for cognition. Acute neuronal damage and chronic apoptosis underlie these deficits, especially in the dentate gyrus (DG) and its medial/lateral perforant pathways (MPP/LPP) substructures, whose electrical inputs are essential for adult neurogenesis. Cannabinoid one receptors (CB1Rs) and Transient Receptor Vanilloid Protein 1 (TRPV1), part of the endocannabinoid system (EC), regulate synaptic plasticity in MPP/LPP due to the high concentrations each receptor has in the DG. Altered EC signaling in mTBI models contributes to excitotoxicity. Pharmacological tools for targeting CB1Rs (AM251) and TRPV1 (AMG9810) reveal the receptor’s effects indirectly before and after r-mTBI. 53 Sprague Dawley rats were used for recordings, with ninety-nine slices used. Animals were split across six groups (Sham/r-mTBI controls, plus corresponding drug groups). Sham/r-mTBI controls only showed differences in LTP induction, with mechanistic properties of the synapse appearing unchanged via paired pulse and short-term potentiation (STP) recordings. Both AMG9180 and AM251 restored LTP deficits seen between Sham/r-mTBI controls, while TRPV1 also significantly enhanced STP levels, and removed paired-pulse facilitation effects seen in Shams. This suggests that both receptors can be pharmacologically manipulated to aid in synaptic plasticity deficits following r-mTBI, as well as suggesting that both receptors are downregulated following r-mTBI.
Investigating the environmental and anthropogenic drivers of temperate reef grazers and developing a grazer-based metric for assessing reef health
(2025) Jones, Alec E.
Grazers structure ecosystems by consuming primary producers. Recently, human-induced predator loss has caused destructive overgrazing of foundational species by grazers. Kelp forests are one critical ecosystem that has been affected, where red sea urchin (Mesocentrotus franciscanus) grazers have overconsumed many areas, resulting in barren habitats. Importantly, not all grazers in these ecosystems remove the kelp canopy; species such as the red turban snail (Pomaulax gibberosus) merely graze on biofilms or remove small patches leaving the kelp blades intact. Given the disruptions (e.g., predator loss) to normal grazer controls, identifying key factors regulating grazer populations is crucial to inform conservation action. We investigated potential environmental and recreational fishing drivers of red sea urchin and red turban snail density on rocky reefs. We predicted that temperature and wave exposure would negatively affect grazer density, and that grazer density would be lower on loose seafloor. We also predicted lower urchin density and higher snail density in protected areas, where limited fishing promotes higher trophic levels and larger-bodied predators. We found a strong negative relationship between turban snail density and wave exposure, suggesting turban snails may be impacted by increases in wave energies. Conversely, urchin density was not significantly associated with any of the environmental variables tested, supporting that this species tolerates a wide range of environmental conditions and can maintain high densities over diverse regions without management intervention. Indeed, we found that protected areas with reduced fishing pressure returned significantly higher snail-to-urchin ratios, translating into healthier ecosystems and intact kelp forest communities. Reduced fishing pressure likely contributed to more complete predator communities in protected areas, which can improve urchin control, leading to increased macroalgal growth and snail densities. Our results support the role of protection from fishing as a key management strategy that can regulate damaging urchin populations and promote healthier reef communities.
Ontogenetic shifts in the diet of commander squid (Berryteuthis magister) in the Salish Sea revealed through stomach content and stable isotope analyses
(2025) Hummelbrunner, Elise
Cephalopods play crucial roles in marine ecosystems, yet their dietary habits remain underexplored in many regions. This study examines ontogenetic shifts in the diet of Berryteuthis magister (commander squid) within the Salish Sea using stomach content and stable isotope analyses. Squid samples were obtained through Fisheries and Oceans Canada midwater trawl surveys, and their dietary composition was assessed across different size classes. Stomach content analysis revealed a dietary transition occurring at approximately 160 mm dorsal mantle length (DML), where individuals shift from a crustacean-dominated diet to increased piscivory. This shift was confirmed by stable isotope analysis, which demonstrated a sigmoidal increase in δ¹⁵N values, corresponding to an approximately one trophic level rise with growth. The study found no significant dietary differences between sexes or sampling locations. These findings indicate that B. magister is not merely an opportunistic feeder but a selective predator, actively adjusting its foraging strategy in response to prey availability, capture efficiency, and energetic demands. This research provides the first comprehensive analysis of ontogenetic dietary shifts in B. magister in the Salish Sea, highlighting its role as both competitor and predator in structuring marine food webs. Understanding these trophic interactions is essential for refining ecological models and assessing broader ecosystem dynamics in the region.
Commercially and ecologically valuable forage species selectively use shallow nearshore habitats at fine spatiotemporal scales
(2025) Gregr, Isabel R.
Nearshore ecosystems provision food and habitat for a diverse community of resident and migratory species, that in turn support coastal fisheries and economies. However, the spatial and temporal dynamics of habitat use by nearshore species are poorly understood in many areas as traditional underwater survey methods (e.g., SCUBA) only capture a snapshot in time, with many species difficult to observe in situ. Using timelapse cameras at six sites across two regions on a large nearshore shelf within a temperate inland sea, the Strait of Georgia, we determined community composition and the presence and abundance of forage species between 7 am and 7 pm during the summer of 2024. Timelapse images were paired with environmental data (temperature, current speed) to investigate how abiotic factors influenced dominant forage species. We quantified 16 taxa, including eight groups of forage fish. Community composition varied significantly over time and between regions, with forage species such as Clupea pallasii (Pacific herring) dominant earlier in the season and Doryteuthis opalescens (opalescent squid) dominant later, with these species being more abundant at different regions. Regional and temporal differences demonstrate that relatively small variations in environmental conditions can affect community composition, underscoring the need for fine-scale monitoring to inform site- and species-specific management. Pacific herring and opalescent squid showed distinct habitat use as the season progressed, with evidence of environmental factors influencing species distributions, particularly during spawning and juvenile stages. Increased temperature negatively influenced herring presence, while increased current had the opposite effect. Conversely, increased current negatively influenced squid presence. These findings have implications for predator-prey interactions, with the distributions of herring and squid likely influencing the presence of their predators, including salmon and rockfish. As climate change continues to alter ocean conditions, understanding how these species respond to environmental variability is essential in predicting shifts in their distributions.
A comparison of drought tolerance in two conifers with contrasting mycorrhizal associations
(2023) Robson, Bethany
Drought events are increasing in frequency, severity, and distribution as a result of climate change. Plants have a variety of adaptations to water stress, including symbioses with mycorrhizal fungi. Little is known about how the type of mycorrhizae (arbuscular or ecto-) may affect drought tolerance, especially in conifers that are restricted in what association they can make. Research suggests that there may be an effect of mycorrhizal type on drought tolerance, and that mechanisms for this may be different in arbuscular and ecto- mycorrhizae. The objective of this study was to determine how the type of mycorrhizae may affect drought tolerance in Pinus contorta and Thuja plicata, species that make contrasting mycorrhizal associations. Three experiments were performed using both aeroponics and traditional soil culture to explore the effects of mycorrhizal association on drought tolerance. P. contorta performed consistently better in all experiments when compared to two populations of T. plicata from different ecozones in British Columbia. Quantum yield declined linearly with increasing drought stress in both treatments with mycorrhizal colonization, and non-linearly in the treatment with no colonization. These trends were consistently shown across all seedling populations, which suggests that both types of mycorrhizal symbioses are important in the drought tolerance of these species. Further investigation is needed to determine how mycorrhizae may influence recovery after drought in these species, as well as the mechanisms mycorrhizae may use to improve drought tolerance in host plants like P. contorta and T. plicata.
Calabindin and channelrhodopsin-2 expression in the dopaminergic SNC and VTA of DAT-CRE
(2023) Waller, Olivia
The DAT-Cre::ChR2-EYFP mouse model has recently emerged as a useful tool to investigate the function of the dopaminergic (DA) system, which is known to be involved in motor behaviour, motivation and reward, memory, and cognition. This is accomplished through selective expression of channelrhodopsin-2 (ChR2), a blue light-activated cation channel, in DA neurons. DA neurons that express calbindin (Calb), a calcium-binding protein, make up a discrete subpopulation with unique functional characteristics. Functional and physiological heterogeneity between the substantia nigra pars compacta (SNc) and ventral tegmental area (VTA) has been well documented, and past research conducted by the Nashmi lab has observed physiological heterogeneity between DA neurons along the mediolateral axis of the SNc itself. Therefore, there may be potential for Calb to act as a marker for distinct physiological cell phenotypes. Here, we evaluate the DAT-Cre::ChR2-EYFP model’s efficiency in expressing ChR2 within DA neurons and characterize the colocalization of Calb in DA neurons within the VTA and along the mediolateral axis of the SNc. We used confocal fluorescence microscopy of DAT-Cre::ChR2-EYFP brains and quantified tyrosine hydroxylase (TH), ChR2, and Calb expression within regions of interest. No significant difference in Calb colocalization in DA neurons was found between the medial and lateral SNc, although a large difference was observed between the SNc and VTA. We also report a that the DAT-Cre::ChR2-EYFP mouse model is extremely efficient in expressing ChR2 in DA neurons of the midbrain.
What stress sequence kills: different sequences of cold and freshening stress with varying latency periods and mortality of Tigriopus californicus copepodids
(2023) Krohman, Rebecca
Anthropogenic activities are increasing the number of extreme events in nature prompting researchers to study how multiple stressors impact animals. Currently, few studies have researched sequential stressors. However, in nature, stressors generally act one after another making sequential stressor studies increasingly more important to properly inform management practices. Responses of animals can change when stressors are applied in different sequences and with different amounts of time in benign conditions (latency time) between stressors. I test how mortality changes with different sequences of 12-hour cold (-15 °C change) and freshening (34% salinity of seawater) stress with three latency periods of 0, 12, and 24 hours. I use a model organism without laboratory rearing for physiology, Tigriopus californicus, which is an abundant harpacticoid copepod found in high intertidal splash pools. I find that hypo-salinity has a more severe effect than cooling disturbance and that stress sequence changes the mortality of T. californicus. In particular, there was high fatality in stress sequences that included freshening while individuals survived better in sequences that only had cold stress. The low recovery in hyposaline water shows that T. californicus had a poor capacity to osmo-regulate in 12 ppt hypoosmotic surroundings while the low mortality observed following cold stress indicates individuals were adapted for temperatures below freezing. Furthermore, there was a positive relationship between survival and latency time when hypoosmotic conditions were applied before low temperature stress showing that exposure to hypoosmotic extremes increases the ability of T. californicus to withstand cold. My results support the hypothesis that the sequence of extreme events and timing between stressors may change whether an organism lives or dies. This research adds to studies of multiple stressors and can be important for reference to future studies investigating sequence effects.
Investigating the influence of repeated mild traumatic brain injury on sensorimotor deficits and synaptic plasticity in the dentate gyrus of young adult female and male rats
(2023) Seusser, Kirsten
The prevalence of mild traumatic brain injuries (mTBIs) has raised a serious public health concern particularly in young adults engaged in contact sports. Using Sprague Dawley rats as a model organism, this study has sought to determine if lateral impact repeated mTBI (LI-RmTBI), a method which induces linear and rotational forces, modulates synaptic plasticity in young adult rats using in-vivo electrophysiological techniques. It also set out to investigate whether significant sex-dependent effects exist, and add to the small pre-existing hippocampal research base of data collected from female rats. While no significant differences in loss of consciousness (righting reflexes), synaptic plasticity (short-term and long-term potentiation), neurotransmitter release (paired-pulse), nor post-synaptic responsiveness (input/output) mediated by LI-RmTBI as a function of sex were observed. Sensorimotor tests (neurological assessment protocols) immediately following mTBIs demonstrated that mTBI groups performed significantly worse than their respective sham controls as the result of mild concussive forces. This result is supportive of the need for additional LIRmTBI experimentation to garner a better understanding of pathophysiological outcomes over a broader range of injury severities. In experimental findings of mTBI examined as a function of sex, significant differences were observed whereby mTBI males fared worse than their female counterparts for acute neurocognitive function. This clearly highlights the need for more favourable inclusion of females within research studies to better understand the diversity of outcomes as a function of sex, and appropriate clinical applications for treatment.
Mating system and niche breadth in sister species of Erythronium in the Pacific Northwest: a study using Ecological Niche Modelling
(2022) Quayle, Spencer
Ecological niche models were used to compare the climatic niche breadths of Erythronium oregonum & Erythronium revolutum, sister species in the family Liliaceae native to western North America. The former is more outcrossing, while the latter is more inclined to self-pollinate. Herbarium records and iNaturalist data were compiled and fed into the niche modelling software Maxent. Analysis of the output reveals that the selfer, E. revolutum, occupies a broader niche than the outcrosser, E. oregonum. Further niche characterization demonstrates that the two sisters are divided in their climatic preferences and constraints, with E. revolutum favouring cooler, wetter, and less seasonal conditions. Possible reasons for this difference in niche breadth are discussed, although much historical, genetic, and biotic context remains open to further research.
Local environmental conditions predict spatial transitions in seaweed community composition in a rocky intertidal ecosystem
(2022) Spriel, Brittnie
Kelp forests are considered the most vulnerable temperate marine ecosystems to climate change, and recent marine heatwaves have caused considerable kelp losses. Globally, heat stress has induced phase shifts from kelp to more heat-tolerant turf algae ecosystems with less structural complexity, resulting in a loss of food, habitat, and productivity. Currently, the relationships between temperature and intertidal kelp and turf species in the Northeast Pacific is not thoroughly understood, as majority of research has focused on subtidal kelp abundances over temporal scales. Here, I investigated how a spatial temperature gradient of ~6 oC, combined with local variation in wave energy at sites within Barkley Sound, Vancouver Island, B.C., influences the abundance of kelp and turf algal species in the rocky intertidal. High kelp cover was primarily observed at sites with the lowest water temperatures, and at sites with high wave energy relative to other sites with similar local temperatures but low wave energy. Accordingly, I found that the percent of kelp cover, as well as kelp diversity (measured as species richness, Simpson diversity, and Shannon diversity) were all significantly negatively influenced by temperature, and positively influenced by wave energy. No kelp species were found at sites above 15.8°C, and Egregia menziesii was the only species to be found across all sites that contained kelp. These results indicate that kelp is negatively influenced by increasing temperatures, and that high wave energy may act to ameliorate heat stress. In contrast, turf cover was significantly negatively correlated with kelp cover, such that turf cover was significantly greater at sites with higher temperature and lower wave energy. The results indicate that on a spatial scale, an increase in temperature, combined with variation in wave energy, significantly drives the absence of kelp species, and further the dominance of less structurally complex turf algae. These significant effects of local environmental variation could have implications for how climate change may be negatively influencing the structural complexity of seaweed communities in the rocky intertidal.
Characterizing how intermittent and single periods of fasting affect age-related reproductive decline in Caenorhabditis elegans
(2022) Motkoski, Saige
The physiological decline associate with aging is observed relatively early in the reproductive system. The initial stage of age-related reproductive decline is partly due to oocyte deterioration, and may provide insights into aging on a broader scale. Nutrient-sensing signaling pathways are crucial for adjusting somatic and reproductive tissue growth and maintenance during natural variations in food availability. Dietary restriction (DR) approaches such as intermittent fasting (IF) or a single period of fasting (SPF) can induce lifespan extension in the nematode Caenorhabditis elegans. However, it is not known if IF or SPF will similarly delay C. elegans reproductive decline. Interestingly, it has previously been found that hedgehog-related gene wrt-10 is upregulated in response to fasting, and a separate study showed that wrt-10 overexpression can delay phenotypes of reproductive aging. It is not yet known if wrt-10 acts to mediate IFinduced lifespan extension, or plays a role in regulating reproductive function under fasting conditions. To characterize the impacts of fasting on reproductive aging and clarify the mechanism of IF-induced lifespan extension, I subjected worms with and without functional wrt-10 to IF or SPF nutrient conditions. I unexpectantly found that IF does not significantly extend lifespan under the experimental conditions used here. Instead, I found that IF and SPF can have detrimental consequences for behaviour, physiology, and reproductive capacity. These detrimental consequences highlight that reproductive decline should remain an integral aspect of aging research. Worms with non-functional wrt-10 had a survival advantage in late adulthood and conversely accelerated reproductive decline, suggesting that wrt-10 may play alternative roles in somatic or reproductive tissue maintenance. These key findings contribute to an understanding of the interplay between nutrition, longevity, and reproductive decline.
Seasonal dynamics of an urban leafhopper community in Metchosin, British Columbia: Investigating diversity trends, parasitoid (Hymenoptera: Dryinidae) relationships, and the potential for a definsive symbiosis
(2022) Hickli, Hannah
Descriptions of leafhopper (Auchenorrhyncha: Cicadellidae) communities in non-agricultural urban environments are lacking, despite leafhoppers being diverse and abundant members of cosmopolitan trophic webs. As abundant herbivores, leafhoppers have the potential to form associations with defensive endosymbionts that mediate trophic interactions with their natural enemies. This study provides the first description of leafhopper diversity and their associations with dryinid parasitoids (Hymenoptera: Dryinidae) in Metchosin, British Columbia. Using morphospecies sorting and barcoding of mitochondrial gene cytochrome c oxidase I, 23 taxa were shown to form a community dominated by generalist leafhoppers Dikraneura mali and Ribautiana debilis (Typhlocybinae). Seasonal trends, including periods of highest abundance, species richness, and parasitism, were largely consistent over two years of collection, peaking in late September, late June, and August/September, respectively. The largest difference between years was found in leafhopper abundance and rates of occurrence of dryinid parasitoids. Parasitism rates suggest dryinids may be an important natural enemy of R. debilis in this community and a previously unknown association was revealed between hosts R. debilis and D. mali and their unidentified dryinid parasitoid. Examining the 16S rRNA amplicon libraries of D. mali and R. debilis revealed a Rickettsia bellii-like endosymbiont with 100% infection frequency in a subset of D. mali and a Wolbachia endosymbiont in R. debilis. Trophic interactions of leafhoppers, dryinids, and symbionts in this community deserve further investigation.
Confirmation of UGT71L1's role in salicinoid biosynthesis using transgenic rescue and overexpression poplars
(2022) Loland, Megan
Salicinoids are phenolic secondary plant metabolites unique to the family Salicaceae. Their structures and functions as insect defense compounds are well known, but their biosynthetic pathway has yet to be fully understood. Recently, a UDP-glycosyltransferase, UGT71L1 was knocked out in poplar hybrid plants and they were found to have a major unexpected phenotype change including shrunken leaves and dwarfed height. Also, the concentrations of salicinoids were greatly decreased suggesting that UGT71L1 is essential for salicinoid biosynthesis. Here, UGT71L1 rescue plants, which complemented the mutation, were created and demonstrated a return to wildtype phenotype. This confirmed that the sole cause for the phenotype change was the loss of UGT71L1 and not a result of off-target effects of the transformation. UGT71L1 overexpression plants created from wildtype plants demonstrated that high UGT71L1 levels do not directly alter plant morphology, as expected, although the possibility was raised that UGT71L1 could be a limiting factor. Chemical analysis of the knockout lines suggested the possibility of minor involvement of another glycosylase in the larger salicinoid synthesis pathway. The knockout lines and a partial rescue line contained significantly higher salicylic acid-glucoside (proxy for salicylic acid) concentrations compared to all other lines. Therefore, it was inferred that salicylic acid is likely the cause of phenotypic change and salicylic acid may be linked to the salicinoid pathway. UGT71L1's role in salicinoid biosynthesis is confirmed as crucial, although further research into its effect on salicylic acid and salicin metabolism are necessary in order to advance the understanding of the salicinoid biosynthetic pathway.
Host benefits of a novel endosymbiont: Interactions between a defensive spiroplasma and a specialist nematode in Drosophila
(2022) Hyggen, Thompson
Bacterial endosymbionts are widespread in insects, and can affect their hosts in many different ways, such as protecting them against diverse natural enemies. Drosophila flies host Spiroplasma symbionts that defend them from parasitic wasps, as well as a harmful, generalist nematode parasite. However, defence has never been tested for a specialist nematode, Parasitylenchus nearcticus, which can be equally or more damaging to its hosts, with infection often resulting in complete sterility. Here, I exposed Spiroplasma-positive and negative Drosophila putrida flies to P. nearcticus to test if this symbiont confers protection against this parasite. I measured infection success by counting the number of infective worms that successfully parasitized their hosts, and parasite fitness by counting the reproductive output of motherworms. I also measured the effect of nematodes on Drosophila fitness by counting the number of mature fly eggs. Although P. nearcticus infected its natural host, Drosophila subquinaria, at high rates in my experiment, infection rates in D. putrida were very low, limiting my ability to demonstrate any defensive effects of Spiroplasma against this nematode. However, I did find lower nematode fecundity in the one infected fly that harboured Spiroplasma, which contained few, sickly-looking nematode offspring. Interestingly, I also found that Spiroplasma-infected D. putrida flies had higher fecundity than symbiont-free ones, independent of nematode infection. This research provides multiple pieces of evidence for how Spiroplasma can benefit their hosts and will help guide future investigations in defensive symbiosis.
The relationship between Parkinson's disease and prostate cancer and examining artificial light at night as a potential environmental risk factor
(2022) Elarid, Sydney
The incidence rates of Parkinson's disease (PD) and prostate cancer (PC) are rapidly increasing with global urbanization. Some studies have suggested but not confirmed there may be common risk factors shared between the two diseases. Also, epidemiological country wide studies have found these two diseases to be correlated, but few studies have explored this possible correlation over a continent. The first objective of the present study is to explore the possible correlation between PD and PC over continental Europe. While the second objective is to search for potential risk factors that might be common to both PD and PC. This study attempts to clarify one of the possible common risk factors associated with these debilitating diseases, namely artificial light at night (ALAN). By examining and understanding the environmental risk factors associated with the etiology of PD and PC, we can suggest preventative environments to promote better health for the millions of individuals affected globally by these pathologies. The present study will use artificial light at night (ALAN) data gained from orbiting satellite sensors to calculate the average ALAN/person values for each country under investigation. Countries of interest include 42 European countries. PD and PC country rates were obtained from the Global Health data exchange, providing the prevalence, incidence, and mortality rates from 1990 to 2019. The frequency of internet usage data will come from Eurostat and serve as an alternative marker for exposure to ALAN. The prevalence, incidence, and mortality rates for PD and PC in combination with the average ALAN/person values and average frequent internet use will provide the framework for determining significant predictors of PD and PC using multivariable linear models. When considering all 43 countries over 29 years, the rates of prevalence and incidence between PD and PC were positively correlated between PD and PC (r=0.61 and 0.45, respectively; p < 0.05). However, when looking at individual countries, there was a wide range of correlations across the 43 countries, ranging from very strong positive correlations (e.g., in Cyprus, r=0.98) to very strong negative correlations (e.g., in the Republic of Moldova, r= -0.97). When considering ALAN, the average ALAN/person increased over the 29 years and was positively correlated over time (r=0.41). PD and PC prevalence were also positively correlated to the average ALAN/person (rPD=0.24, rPC=0.30). Average frequent internet usage also increased over time (positively correlated over time [r=1.00]), and positively correlated to the prevalence of PD and PC (rPD=0.51, rPC=0.66; p < 0.05). Multivariable modelling indicated that GDP and the percent of the urban population has a significant (p < 0.05) influence on the multivariable models involving ALAN but not internet usage data, and urbanization had no significant effect on the multivariable model predicting PC with ALAN. This research found trends consistent with past research that observed positive correlations between PD and PC rates, the prevalence of PD and PC to the average ALAN/person, and the prevalence of PD and PC to the average frequent internet use. These data support the hypothesis of a possible link of the environmental factor, ALAN, to rates of PD and PC.
The bioactivity of Poplar root extracts as a novel treatment for iron overload in a THP-1 cell culture model
(2022) Anderson, Julie
Iron is an essential element for all living beings. However, either too little or too much iron can be detrimental. Non-protein bound iron is highly reactive due to its ability to easily accept and donate electrons. This makes iron a powerful and essential component in many metabolic and physiological processes, but it also poses a potential oxidative danger. Consequently, iron uptake, storage, and recycling are tightly regulated under normal circumstances. In cases of systemic iron overload, excess iron in the body causes extensive damage to DNA, proteins, and other macromolecules, eventually leading to tissue and organ damage. The current leading treatment for diseases of iron overload in humans is chelation therapy, in which iron chelators, molecules that bind and sequester iron, are administered. However, chelator treatments can have cytotoxic effects, driving the search for novel chelator treatment options. In my research, the potential bioactivity of iron chelators present in poplar root extracts were investigated in a simple iron-overload model using a human leukemia monocytic THP-1 cell line. Root extracts were harvested from poplars grown under iron reduced conditions, which we hypothesise to stimulate biosynthesis of chelators, and iron normal conditions as controls. The impact of these growth conditions on root chelator production was examined. To assess the potential of poplar root extracts as a novel bioactive chelators for iron-overload treatment in humans, we measured the intracellular iron content of THP-1 cells under iron overload conditions and after treatment with the clinically used iron chelator deferoxamine in comparison to root extracts. Intracellular iron normalized to protein concentrations as a proxy for cell number. Intracellular iron concentration, measured using ferrozine, was increased in response to chronic iron treatment relative to control cells grown under iron normal conditions. Relative to cells treated with chronic iron overload, it was found that DFO reduced intracellular iron content of chronically iron overloaded cells by 33% (p = 0.020). Iron normal and iron reduced poplar root extracts also reduced iron content by 17% and 15% on average, but these trends were not significant. There was no significant difference between the iron content of cells treated with either poplar root extract and DFO. Unexpectedly, there was no difference in the iron content of cells treated with extracts from roots of plants grown under iron normal and iron reduced poplar conditions (p = 0.878). Trypan blue staining illustrated that chelator treatments had little effect on cell viability, indicating low cytotoxicity of root extracts. Future investigations of the potential bioactivity of iron chelators present in poplar root extracts should examine the chelating abilities of poplar root extracts with increasing concentration. Furthermore, metabolic characterization of the root extracts would help identify individual compounds of interest, and to improve the effectiveness of the screening process.

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