M.Sc. Biological Sciences
Permanent URI for this collectionhttps://hdl.handle.net/10464/1690
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Item Open Access Sentinel behaviour and urban environments: A corvid’s perspectivePopescu, Alex; Department of Biological SciencesAmerican crows (Corvus brachyrhynchos) are the black-clad rulers of a city’s skies and can be spotted in most North American cities. The abundance of corvids has increased with increasing urbanization, suggesting they benefit from living near humans. Recent literature shows that urbanized species such as the American crow can behaviourally adapt to exploit anthropogenic resources resulting in positive urbanization effects on corvids. While individual-level behavioural adaptations are an active area of research, social behaviour adaptations and their contribution to the success of urbanized species are underexplored. Sentinel behaviour is a social behaviour that could increase a species' survival of group members. Using a scoping review approach, several intrinsic (or internal, e.g. sex or body mass) and extrinsic (or external, e.g. predation risk or anthropogenic noise) factors that can alter the sentinel behaviour of mammal and avian species were identified. Factors that alter an individual’s energetic resources can greatly affect an individual’s ability to perform sentinel behaviour, and factors that increase risk to the individual will increase an individual’s propensity to perform the behaviour. During the summer of 2022, I observed the foraging behaviour of American crows in the presence and absence of a sentinel and in the green and commercial areas of St. Catharines. I found that American crows altered their social foraging behaviour in different urban microenvironments but had fewer significant changes in response to the presence of a sentinel. I found a significant interaction between sentinel presence and generalized environment on the behaviour of foragers, suggesting increased reliance on the sentinel when sentinel behaviour is most effective: in green spaces. My findings highlight the need to consider both intrinsic and extrinsic factors and their interaction when studying social behaviours. My findings highlight the need to continue studying the effects of urbanization on social behaviours. By doing so, future studies could unearth the complex mechanisms behind the evolution of social behaviours and help predict how they could change in an ever-urbanizing future.Item Open Access Regulation of social behaviour via oxytocin receptor signaling in the caudodorsal lateral septum in Long-Evans male and female ratsPirri, Fardad; Department of Biological SciencesThe oxytocin receptor (OTR), a class A G-protein coupled receptor, is highly expressed in the lateral septum (LS), a brain region that regulates social behaviors in rodents. This thesis investigates whether OTRs within the LS modulate social approach-avoidance behavior, acquisition of long-term social recognition memory, and anxiety-like behavior in adult male and female rats. In the first experiment, L-368, 899, a selective OTR antagonist, was infused locally into the caudodorsal lateral septum (LSc.d), resulting in the attenuation of social approach, enhancement of social vigilance, and reduction in social novelty preference in male and female rats, with no effect on locomotion. In the second experiment, carbetocin, a biased OTR/Gq agonist, was locally delivered into the LSc.d, leading to reduced social approach and social novelty preference (a measure of social memory), with no effect on social vigilance or locomotion. Intriguingly, carbetocin increased latency to consumption of a highly palatable food only in male rats in the novelty-induced hypophagia test, indicating the sex-specific anxiogenic effects of the OTR/Gq signaling pathway in the region. In the third experiment, a selective full agonist of the OTR, (Thr4,Gly7)-Oxytocin, was infused into the LSc.d of male rats, resulting in a slight, but non-significant increase in social approach. Unlike the antagonist and the biased agonist, (Thr4,Gly7)-Oxytocin-treated rats showed social novelty preference 24 h after familiarization. Moreover, (Thr4,Gly7)-Oxytocin decreased latency to consumption of a highly palatable food compared to vehicle-treated rats, suggesting anxiolytic effects of the OTR full agonism. In conclusion, the findings suggest that OTR signaling in the LSc.d regulates social approach-avoidance, acquisition of social recognition memory and anxiety-like behavior depending on the activation of a specific upstream signaling arm of the receptor. I demonstrated that the OTR/Gq signaling pathway within the LSc.d promotes social avoidance in both sexes and triggers anxiogenic effects only in males, contrasting with the effects induced by the full agonism of the receptor.Item Open Access Dynamics of Simultaneous Arboviral Infection in Host and Vector CellsGarrido de Castro, Mariana; Department of Biological SciencesIn this study, simultaneous infection dynamics were investigated in mammalian and insect cells. Mayaro virus (MAYV; genus Alphavirus), West Nile virus (WNV; genus Flavivirus), and Zika virus (ZIKV; genus Flavivirus) were the arboviruses used in the pairings. Arboviruses are transmitted by arthropods, and Aedes sp. mosquitoes are vectors of multiple viruses, including all three used in this study. In addition to sharing some of the same vectors, MAYV, WNV, and ZIKV can all infect humans. To understand whether the presence of another virus affected viral infection dynamics, mammalian-derived Vero and insect-derived C6/36 cells were infected with either MAYV and ZIKV or WNV and ZIKV. In nature, a simultaneous infection can occur through either coinfection or superinfection, and both conditions were studied here. Infection dynamics were assessed by quantifying viral RNA production for 6 days following infection, using RT-qPCR. Simultaneous MAYV + ZIKV and ZIKV + WNV infections impacted infection dynamics. Interestingly, the outcomes seen in simultaneous infections of Vero cells were similar for both pairings. Viral accommodation was seen in coinfection conditions, as no change was seen in RNA levels for either virus in the pairing. The order in which the viruses infected the cells changed the outcome in superinfection conditions in Vero cells – viral accommodation was observed when ZIKV was the first to infect the cells, while superinfection exclusion was seen when ZIKV tried to infect Vero cells already infected with either MAYV or WNV. In C6/36, replication differed between the virus pairings studied but did not differ between coinfection and superinfections. Viral interference was observed for conditions where MAYV and ZIKV simultaneously infected C6/36 cells, while virus accommodation was at play when the virus pairing consisted of WNV and ZIKV.Item Open Access Diversity of cover crops in two organic vineyards in the Niagara Region, Canada, as an adaptation measure to climate changeTosato, Diana Ribeiro; Department of Biological SciencesVineyards are agroecosystems of great importance in the Niagara Region, Ontario (Canada). Due to its microclimate, this region is projected to be impacted by climate change with temperature increases, changes in precipitation patterns in all seasons, and greater frequency of extreme weather events. The aim of this thesis was to explore the projected changes for the weather in the Niagara Region, Canada, summarize which seasonal changes are expected and assess how such changes are likely to affect the key components of the vineyard ecosystem (i.e., soil, vines, invertebrates, and pathogens). It is expected that by 2080 the region will experience an increase in temperature in all four seasons; an increase in precipitation during the fall, winter, and spring; and a decrease in precipitation during summer months. Impacts of the projected changes will likely lead to vine water stress, yield loss, increases in incidents of diseases, increases in the spread of new pests, and changes in grape quality ultimately resulting in lower wine quality and/or production. Current management practices will need to be better understood and adaptive strategies introduced to enhance grape growers’ ability to minimize these impacts. The research also aimed to test the performance of four different cover crops in monoculture or in mixture in two organic vineyards. Of the planted species, rye grass and hairy vetch showed a great establishment, while pearl millet did not establish due to weed pressure. The ecological indexes (Shannon, Simpson’s, and Evenness) values showed that there is significant difference in cover crop diversity between growing seasons and collection months (June/September) in Vineyard #2, and in richness in Vineyard #1, indicating fluctuations in community composition over time. These results suggest a dynamic ecosystem response to seasonal and annual variations. These results may be used to increase the knowledge about the expected future for the vineyards in the region in face of climate change, and into one of the alternative management techniques that can help mitigate the impacts of changes in temperature and rainfall increase of extreme events in the region.Item Open Access Determining the effect of different cover crops on nematode communities in vegetable productionAubry, Elyse; Department of Biological SciencesAgricultural soil environments contain different types of nematodes, part of several trophic levels that aid in balancing the soil food web. Beneficial free-living nematodes (FLNs) consist of bacterivores, fungivores, predators and omnivores that help in the mineralization of the soil and the top-down control of damaging plant-parasitic nematodes (PPNs). Conversely, PPNs feed directly on plant roots and cause $125 billion in worldwide crop losses annually, making them a plant pathogen of great concern for growers. Farmers have started to implement the use of cover crops in agricultural systems for the protection and enrichment of soil but research on how different covers affect nematode populations is lacking and in demand. This study aims to determine the effect of legume and grass cover crops, cow pea and pearl millet, as well as their mixture on the abundance and diversity of FLN and PPN populations. Soil samples were taken prior to, during, and after cover crop implementation to analyze nematode communities using morphological and DNA metabarcoding techniques. Results showed that the implementation of cow pea and pearl millet covers as well as their mixture in a spinach agricultural system led to the control of PPNs and the proliferation of FLN communities. Specifically, we found that the mixture of both cover crops and the use of pearl millet as a single species generated healthier nematode populations with significantly less PPNs and more FLNs when compared to the control and fallow plot treatments using both nematode identification methods. However, the choice of cover crop to implement by growers should be based on specific soil health needs to promote a healthy soil and nematode population. Ultimately, understanding how different cover crops impact nematode populations can inform sustainable agricultural management practices. By strategically selecting legume and grass cover crops, farmers can optimize soil health, reduce crop losses caused by PPNs, and promote a balanced soil ecosystem to improve crop productivity.Item Open Access Investigating the Importance of Physiological Cell Culture Conditions in Modeling Cancer Metabolism and Metabolic ReprogrammingGardner, Georgina; Department of Biological SciencesStandard cell culture conditions do not mimic the physiological environment of cancer cells. Traditional culture media contain metabolites at concentrations that far exceed conditions measured in vivo, and oxygen is often unregulated, exposing cells to atmospheric oxygen concentrations (~18%), rather than the 0-3% O2 measured in solid tumours in vivo. Recently, plasma-like media have been developed to address these limitations, aiming to improve culture conditions and maintain biologically relevant cancer phenotypes in vitro. However, these conditions remain unrepresentative of interstitial fluid in solid tumours. The goal of this thesis was to investigate how physiological culture conditions affect cancer cell behaviours, specifically cell metabolism and adaptive metabolic responses. In the first data chapter of this thesis, I explored nutrient exhaustion in physiological plasma-like medium (Plasmax) at 18% and 5% O2, and the adaptive mechanisms by which cancer cells can maintain survival under metabolic stress conditions. Here, I found that glucose and amino acid depletion from Plasmax over 48 hours is associated with several adaptive mechanisms consistent with metabolic reprogramming in vivo. Given these responses, I hypothesized that a media formulation designed using metabolite concentrations from tumour interstitial fluid may modulate metabolic phenotypes in a similar manner, providing a more physiologically relevant culture model for cancerous cells. Data chapter 2 addresses this hypothesis, whereby I formulated a novel cell culture medium using quantitative metabolite data from murine pancreatic ductal adenocarcinoma (PDAC) tumour interstitial fluid, named Tumour Microenvironment Medium (TMEM), and investigated the effects of TMEM and 1.5% O2 on an adapted murine PDAC cell line (KPCY). Importantly, I found that tumour-like conditions elicited a substantial transcriptional and functional response in cultured cells, modulating cell proliferation, migration, glucose utilization, and mitochondrial bioenergetics in ways relevant to in vivo cancer biology. Overall, the results of this thesis highlight the responsiveness of cultured cells to their environment, and the importance of representative culture conditions in the acquisition of biologically accurate experimental data.Item Open Access Tracking nuclear generating station emissions and fossil fuel contributions using tree rings in southern Ontario, CanadaMartin, Danielle S.; Department of Biological SciencesChanging atmospheric concentrations of stable (12C, 13C) and radioactive (14C) isotopes of carbon are an important indicator of the Anthropocene. Carbon from anthropogenic sources can be released to the atmosphere as radiocarbon (14C) from nuclear power and above-ground nuclear weapons testing. Carbon-12 and carbon-13 (12,13C) are derived from fossil fuel combustion in the urban, industrial, and transportation sectors. In Ontario (Canada), ~half of the province’s power generation is derived from three nuclear generating stations (NGS), including Bruce Nuclear Generating Station (BNGS), one of the world’s largest NGS. Thus, understanding the contributions of NGS emissions and fossil fuel use in urban, industrial, and transportation sectors is essential for developing accurate atmospheric carbon inventories in southern Ontario. This study analyzes tree-ring Δ14C (the amount of 14C in a particular sample) as a proxy for atmospheric Δ14C by isolating tree-ring alpha cellulose and using accelerator mass spectrometry (AMS). Results indicate that Δ14C tree-ring signatures from white spruce (Picea glauca) and blue spruce (Picea pungens) can track 14C-enrichment from NGS 14C emissions when comparing peaks in tree-ring Δ14C offset data and 14C emissions during the trees’ growing season. Tree-ring Δ14C signatures are also observed in Canada’s largest urban centre the City of Toronto, which is nearby to Pickering Nuclear Generating Station (PNGS). Conversely, Toronto also experiences fossil fuel contributions and thus is susceptible to the Suess Effect. We observe fossil fuel-derived 12,13C from urban activities via tree-ring Δ14C-depletion. Peaks were also observed in the tree-ring Δ14C offset and PNGS 14C emissions. To determine 14C-enrichment or -depletion, sites are compared to a regional clean-air site (Egbert, Ontario, Canada) and northern hemisphere atmospheric background sites (Northern Hemisphere Zone 1; Jungfraujoch, Switzerland). Tree growing season and meteorology analyses strengthen the validity of this study’s results. Similar Δ14C levels from white spruce tree rings and an Environment and Climate Change Canada (ECCC) air sampler (ρ = 0.9273) were also observed. Thus, tree-ring Δ14C signatures can be used to measure local influences from anthropogenic sources of NGS 14C emissions and fossil fuel contributions to help build an atmospheric carbon inventory.Item Open Access The Behaviour and Ecology of Mosquito VectorsBenton, Nicholas; Department of Biological SciencesMosquitoes continue to vector pathogens to humans around the world. Research into the unique behaviour and ecology of vector species enables new avenues of control to be developed. I examined two mosquito vector species. The first, Coquillettidia perturbans (Walker, 1856), has been incriminated as a competent vector of eastern equine encephalitis virus (EEEV) in North America. The behaviour and ecology of Cq. perturbans is poorly studied due to how difficult it is to study the immature stages. I attempted to collect and rear Cq. perturbans to establish a laboratory colony. A multi-generational colony was not successful in part to high mortality rates in the 1st instar and pupal stage as well as a suspected obligatory diapause in later larval instars. Despite this, it was possible to artificially blood-feed and have them oviposit viable egg rafts, which hatched and developed into 4th instar larvae. Larvae and pupae collected from the field were also able to successfully pupate and emerge into adult mosquitoes. Other aspects: such as oviposition site preference, oviposition rate, hatch rate, and immature morphology were also documented. The second species studied, was Culex pipiens Linnaeus, which is known to be a competent vector of West Nile virus (WNV). Cx. pipiens is considered ornithophilic (bird-feeding) but is believed to switch to mammal blood-meals in the late-summer to early-fall in northern regions. I tested a protocol that could be used for determining the host preference of Cx. pipiens in a laboratory setting. The protocol involves creating an environment that limits distractions to feeding and positional bias while giving equal opportunity to choose between two different blood-meals. A PCR assay for testing the blood meal contents of blood-fed mosquitoes was also developed. When tested with bird blood vs. mammal blood, the laboratory colony of Cx. pipiens fed on bird blood ~60% of the time. The number of detections for each blood-meal in a cage raised questions about factors such as bias within the Cx. pipiens colony itself, highlighting a need to take behavioural factors into account when performing laboratory host preference experiments.Item Open Access Influence of cover crops on invertebrate diversity in Niagara organic vineyardsGullion, Alysha; Department of Biological SciencesCover crops can play different functions in vineyards, such as preventing soil erosion, improving soil health, reducing the need for pesticides, and increasing nitrogen fixation in soils. Despite the potential of cover cropping, little research has been done on the influence of diverse vegetation on invertebrate functional groups. This study aimed to examine the influence of different cover crop species in the diversity of pests, neutral, and beneficial invertebrate species. The first objective of this study was to assess diversity in the invertebrate community and their functional groups in six different cover crop treatments (Trifolium incarnatum, Vicia villosa, Pennisetum glaucum, mixture of T. incarnatum, V. villosa, P. glaucum, Lolium perenne, and spontaneous vegetation) across two different organic vineyards in the Niagara region. The second objective was to test the use of sentinel plants to identify direct interactions between cover crops and invertebrates. These sentinel plants were grown in greenhouse conditions before being introduced into the field. To access the invertebrate communities involved, the deployment of sticky traps, vine sweeps and cover sweeps in June, August and September 2022 was used to obtain a comprehensive idea of invertebrate communities. The results showed that cover crop species, whether grown in monoculture or mixture, did not significantly influence invertebrate diversity and relative proportion of functional groups. Instead, factors such as vineyard management, environmental conditions, and landscape complexity may play a key role in shaping invertebrate community diversity. Additionally, temporal variation played an integral role in influencing the abundance of pest and beneficial morphospecies in both vineyards. Invertebrate interactions on sentinel plants were nonconclusive, leaving potential interactions between cover crops and invertebrates uncertain in terms of sentinel plant deployment. Also, cover crops grown in the interrow of the grapevines were not the sole vegetation species present in the area, making it challenging to attribute performance solely to a singular species in the study. The results of this study indicate how complex and intricate invertebrate community diversity can be in operating applications. Further investigation on cover crop performance in the field is warranted to better understand how they may influence invertebrate community structure dynamics.Item Open Access Investigating the Cellular Responses of Cancer Cells to Physiological and Hypoxic Oxygen ConditionsAlva, Ricardo; Department of Biological SciencesMost incubators used in cell culture do not regulate O2 levels, making the headspace O2 concentration ~18%. In contrast, most human tissues are exposed to 2–9% O2 in vivo (physioxia). The main goal of this thesis project was to gain a better understanding of how supraphysiological O2 levels affect cell behavior in vitro, with a focus on cancer cell biology. Using RNA-seq, I studied how culture in either 5% O2 or 18% O2 affects gene expression in four human cancer cells. I found that O2 level in culture affected hundreds of genes, however, in a largely cell-type specific manner. Further, gene targets of the hypoxia-inducible factors (HIFs) were upregulated at 5% O2 compared to 18% O2 in all cell lines. This led me to investigate how culturing cancer cells at a baseline level of 5% O2 or 18% O2 affects their response to hypoxia (here, 1.1% O2). My results indicate that baseline O2 level substantially affects the transcriptional response of prostate cancer cells (PC-3) to hypoxia. Notably, cells grown in 18% O2 and then exposed to hypoxia showed an enhanced induction of HIF-regulated genes, particularly genes involved in glucose metabolism. This in turn resulted in an enhanced glucose uptake rate of cells taken from 18% O2 to hypoxia, compared to cells preadapted to 5% O2 and then exposed to hypoxia. Finally, while acute hypoxia did not affect proliferation or migration of PC-3 cells regardless of their baseline O2 level, cells preadapted to 5% O2 did show higher proliferation and migration rates compared to cells in 18% O2. We conclude that O2 levels in culture affect gene expression, glucose consumption, and growth in cancer cells, which, in turn, might result in differential sensitivity towards anticancer drugs, highlighting the importance of maintaining physiological O2 conditions in cell culture.Item Open Access Uncovering millennia of wildfire occurrence during the Holocene at local and regional scales in the Northwest Territories, CanadaNesbitt, Lauren; Department of Biological SciencesNorthern ecosystems are experiencing disproportionate impacts of climate change compared to the rest of the globe, primarily due to Arctic amplification. Ongoing climate change is projected to lead to increases in the frequency and severity of wildfires in the boreal forest. Records of past wildfires in the Northwest Territories, Canada, are spatially limited and temporally short, making it difficult to assess the impacts of wildfires on a long-term basis. Using paleolimnological techniques, including the analysis of macroscopic charcoal, pollen, temperature reconstructions and solar insolation values, local and regional scale wildfire and vegetation histories were constructed for the Northwest Territories. For the local scale study, the charcoal record produced from lake 18-YK-16 (unofficial name) recorded 36 wildfire events during the past ~9,500 years before present (BP), and from lake 18-YK-20 (unofficial name), 62 wildfire events were recorded during the past ~10,300 years BP. For both lakes, wildfire events increased in frequency ~8,000 and ~5,500 years BP, corresponding to the presence of spruce (Picea spp.) and increasing temperatures. Additionally, for 18-YK-16, a third peak in wildfire activity coincided with the Medieval Climate Anomaly 800-1200 CE. Fire occurrence declined during the middle to late Holocene (~5,500-600 years BP) which is a period of climatic cooling. For the regional scale study, wildfire activity was limited during the Late Pleistocene to early Holocene, due to receding glaciers and a lack of vegetation on the landscape. Between ~7,000 years BP and ~5,500 years BP, wildfire activity in the North Slave Region was frequent due to the expansion of fire-prone Picea and higher temperatures. Regional wildfire activity declined throughout the Neoglacial period (~4,500 years BP); however, local-scale wildfires were occurring which can be attributed to the expansion of Pinus ~4,500 years BP in addition to local scale bottom-up and top-down controls. Wildfire activity remained low up until the late 20th century, which can be correlated to increasing temperatures and anthropogenic activities. Long term implications of wildfire activity suggest that with continued warming of the climate, wildfire frequency and severity will increase.Item Open Access Influence of cover crops on invertebrate diversity in Niagara organic vineyardsGullion, Alysha; Department of Biological SciencesCover crops can play different functions in vineyards, such as preventing soil erosion, improving soil health, reducing the need for pesticides, and increasing nitrogen fixation in soils. Despite the potential of cover cropping, little research has been done on the influence of diverse vegetation on invertebrate functional groups. This study aimed to examine the influence of different cover crop species in the diversity of pests, neutral, and beneficial invertebrate species. The first objective of this study was to assess diversity in the invertebrate community and their functional groups in six different cover crop treatments (Trifolium incarnatum, Vicia villosa, Pennisetum glaucum, mixture of T. incarnatum, V. villosa, P. glaucum, Lolium perenne, and spontaneous vegetation) across two different organic vineyards in the Niagara region. The second objective was to test the use of sentinel plants to identify direct interactions between cover crops and invertebrates. These sentinel plants were grown in greenhouse conditions before being introduced into the field. To access the invertebrate communities involved, the deployment of sticky traps, vine sweeps and cover sweeps in June, August and September 2022 was used to obtain a comprehensive idea of invertebrate communities. The results showed that cover crop species, whether grown in monoculture or mixture, did not significantly influence invertebrate diversity and relative proportion of functional groups. Instead, factors such as vineyard management, environmental conditions, and landscape complexity may play a key role in shaping invertebrate community diversity. Additionally, temporal variation played an integral role in influencing the abundance of pest and beneficial morphospecies in both vineyards. Invertebrate interactions on sentinel plants were nonconclusive, leaving potential interactions between cover crops and invertebrates uncertain in terms of sentinel plant deployment. Also, cover crops grown in the interrow of the grapevines were not the sole vegetation species present in the area, making it challenging to attribute performance solely to a singular species in the study. The results of this study indicate how complex and intricate invertebrate community diversity can be in operating applications. Further investigation on cover crop performance in the field is warranted to better understand how they may influence invertebrate community structure dynamics.Item Open Access Investigating Vitis sp. cold stress tolerance with abscisic acid (ABA) analogsGunn, Alexandra; Gunn, Alexandra; Department of Biological SciencesThe sustainability of Vitis sp. grapevine cultivation is threatened by climate change with pressure mounting on low temperature stress adaptations. Abscisic acid (ABA) is hypothesized to act as a central mediator of dormancy status and cold tolerance of grapevine buds. With one or more modifications to the chemical structure of ABA, synthetic analogs can improve its bioactivity in planta. The current research is founded in a comprehensive investigation on dormant grapevine bud cold stress responses following the administration of 8’-acetylene ABA (ABA-1017) and tetralone ABA (ABA-1016). Using V. vinifera (cv. Merlot) and interspecific Vitis hybrid (cv. Marquette) as freeze sensitive models, this thesis set out to determine: (1) the seasonal effect of ABA analogs on the resistance to losing cold tolerance; and (2) the impact of these products on bud dormancy physiology in relation to ABA catabolism. A record of five consecutive seasons (2017-2022) of differential thermal analysis data (DTA) was utilized to perform correlational test on the estimated low temperature exotherm (LTE) to the average minimum field temperature in deacclimation. Water content was measured for untreated, ABA-treated, and ABA analog-treated buds throughout the 2020-2021 and 2021-2022 dormant seasons. Samples were collected in alignment for hormone profiling (LC-MS/MS) to quantify the relative levels of ABA, its metabolites, and the degree of analog uptake/residual following application. Single-node cuttings from treated vines were maintained in a controlled environment (25°C, 16-hour light) to monitor the progression of dormancy against a fixed time-to-event threshold of 50% bud break over a 60-day observation window. Results suggest: (1) ABA analogs can improve deacclimation resistance and delay bud break, but their effect is inconsistent from year-to-year and varies in response to extreme cold stress; and (2) water availability and hormonal status are impacted by the application of ABA analogs unpredictably, and results from dormancy status evaluations are inconclusive to determine the impact of these products on the endo-ecodormancy transition of buds. This research ultimately lays the foundation to continue to explore the hallmarks of Vitis sp. bud dormancy and cold tolerance coordinated by ABA and develop an optimized freeze/frost-mitigation strategy for cool climate grape growers.Item Open Access Characteristics of dominance: behaviours and hormones in a facultatively social bee species (Xylocopa virginica)Mesich, James; Department of Biological SciencesIn facultatively social species such as Xylocopa virginica (eastern carpenter bee), individuals can breed either on their own or in groups, where resources are monopolized by a single dominant female. As such, we would expect that natural selection would act strongly in this species to promote traits that would make females more dominant. This thesis sets out to determine the characteristics that make female X. virginica dominant both through behavioural assays and hormonal manipulation. I paired females with non-nestmates in dyads consisting of two dominants, two subordinates or one of each, during two separate years. I found higher levels of tolerance in dyads without a dominant female in them, but no difference in aggression between dyad types, which would have been expected if dominants tended to be the most aggressive. Behaviours also differed between years with the high population density year having higher levels of aggression and tolerance overall. Clearly many factors contribute to how female X. virginica interact with potential rivals, beyond simply their level of dominance. I also treated females with a Juvenile Hormone (JH) analogue, methoprene, to determine whether it increases ovarian development in this species, as it does in other Hymenoptera. Increased dose of methoprene lead to increased ovarian development in X. virginica, making treated individuals better able to lay eggs and therefore to take advantage of being in a dominant social position. There was no lethal or negative sublethal effects on treated bees meaning that this method could be used in the future for field testing in this species. I suggest that X. virginica dominance is not defined solely by aggression. There are many ways for females to gain a dominant position, and females that are not aggressive enough on their own to fight their way to a dominant position are likely to use other behaviours such as nestmate feeding to gain dominance. The outcomes of this study highlight why dominance and the factors leading to it should be considered closely for the specific species being studied, because aggression is shown to not be the main source of dominance in X. virginica.Item Open Access A comparison of blue vane trap, timed targeted netting, and timed photographic collection methods for evaluating Canadian bumble bee diversityArmistead, Jocelyn; Department of Biological SciencesBumble bee (genus Bombus) populations across Canada are experiencing increases and decreases in abundance; some species are becoming more common while others are at risk of extirpation or extinction. It is important to monitor population changes so that extirpation and extinction can be prevented. Current population assessments for bumble bees, when conducted, use many different collection methods, but this limits our ability to compare across studies and understand trends. There is a call within the scientific community to create a national standard method for collecting bees. The goal of this research was to provide a recommendation for which collection methods could be used across Canada for bumble bee assessments, including assessments of species at risk. Three collection methods, blue vane traps (BVTs), timed targeted netting, and timed targeted photography, were compared with the objective of determining which method provided good diversity information, detected at-risk species, and required low sampling effort. To assess the universality of method performances across the country, surveys were conducted in three different regions of Canada, the Carolinian portion of the Mixedwood Plains Ecozone (southern Ontario), the Prairies Ecozone (Saskatchewan), and the Boreal Shield Ecozone (Newfoundland and Labrador). With some exceptions, the general structure of surveys was that BVTs were deployed for 1 week at a time, and multiple 30-minute netting and photographic surveys were conducted during each collection week. Regional differences were apparent. In the Prairies Ecozone BVTs collected the most specimens while in the other regions BVTs collected the fewest. BVTs detected the most species in the Carolinian and Prairies Ecozones, but netting detected the most species in the Boreal Shield Ecozone. For all regions, BVTs were the most efficient method at low sample sizes when compared using rarefaction. BVTs also detected the most species at risk. Distinct species compositions produced by BVTs compared to netting and photos demonstrated complementarity between these methods. Netting and photo species distributions also differed from each other in most regions. The overall recommendation when assessing Canadian bumble bee populations is to use BVTs in week-long durations with either netting or photo surveys to complement them.Item Open Access The Role of Retinoic Acid in the Formation and Modulation of Invertebrate Electrical SynapsesWingrove, Joel; Department of Biological SciencesCommunication between cells in the nervous system is dependent upon structures known as synapses. Synapses are broadly characterized as either chemical or electrical in nature, owing to the type of signals that are transmitted across them. Factors that can affect chemical synapses have been extensively studied. However, the factors that can influence the formation and modulation of electrical synapses are poorly understood. Retinoic acid, a vitamin A metabolite, is a known regulator of chemical synapses, yet its capacity to regulate electrical synapses is not as well established. Preliminary evidence from the central neurons of both invertebrates and vertebrates suggests that it is also capable of regulating the strength of electrical synapses. In this study, I provide further insights into how retinoic acid can act as a neuromodulator of electrical synapses. My findings suggest that retinoic acid is capable of rapidly altering the strength of electrical synapses in a dose- and isomer-dependent manner. Further, I provide evidence that this acute effect might be independent of either the retinoid receptors or a protein kinase. In addition, I provide novel findings to suggest retinoic acid is also capable of regulating the formation of electrical synapses. Long term exposure to two isomers of retinoic acid, all-trans-retinoic acid and 9-cis-retinoic acid, reduces both the proportion of cell pairs, and the average synaptic strength between cells that form electrical synapses. In summary, these investigations provide novel insights into the role that retinoids play in the both the formation and modulation of electrical synapses in the CNS.Item Open Access Interactions between caffeic and caftaric acids, furan-derived aroma compounds, and chitosan during base wine ageingMedeiros, Jacob; Department of Biological SciencesDuring sparkling wine ageing, chemical changes take place that alter the composition of the wine, creating nutty, roasted, and caramel aromas and flavours not previously detected in young wines. Furan-derived aroma compounds, a group of odor-active chemicals formed during the long-term storage of wine, contribute to these empyreumatic aroma changes. Hydroxycinnamic acids (HCAs) such as caffeic and caftaric acid, known to be responsible for oxidative browning in wine, also influence the formation of furan-derivative aroma compounds in model wine solutions. Additionally, sparkling wine research using chitosan has been shown to influence the formation of furfural, a furan-derivative thought to contribute a caramel aroma to aged wine. This project had three aims: To determine (1) the impact caffeic and caftaric acid have on furan-derived compound formation during base wine storage, (2) the ability of mushroom-derived chitosan to reduce caffeic and caftaric acid concentrations in Pinot noir juice, and (3) to establish whether chitosan added to base wine influences the generation of furan-derived aroma compounds during storage. For Aim 1, Chardonnay (2019) base wine was stored at 15 and 30 °C for 90 days with additions of fructose, caffeic acid, and caftaric acid independently, or in combinations. Results showed that at 15 and 30 °C, furfural increased slightly with 5 mg/L additions of caffeic and caftaric acid. For Aim 2, Pinot noir juice (2021) was stored at 10 °C for 18 hours with 1 g/L additions of < 3 kDa, 250 kDa, and 422 kDa molecular weight (MW) chitosan, before being racked off prior to fermentation. In the finished wine, < 3 kDa chitosan treatment decreased caftaric acid and increased the amino acids, while the 250 kDa chitosan decreased total HCA estimation, turbidity, and brown pigmentation compared to the control. For Aim 3, Pinot noir (2021) base wine was stored at 15 and 30 °C for 90 days with the aforementioned chitosan treatments. All three MW chitosan treatments at 30 °C substantially increased furfural, homofuraneol, and 5-methylfurfural generation relative to the control. At 15 °C, furfural and homofuraneol were also found at greater concentrations in the chitosan-treated wine. Overall results show (1) Slight modulation of furan-derived compounds due to increased caffeic and caftaric acid concentrations, (2) The reduction of caftaric acid by a low MW chitosan prior to fermentation, and (3) An increase in furan-derived compounds in base wine treated with chitosan during short-term storage. The findings of this thesis determined for the first time the influence of HCAs and chitosan on the concentrations of aroma and flavour compounds, with real applications into the acceleration of ageing in sparkling wines.Item Open Access Role of Viral Infections in Rapid Prunus Decline in the Niagara RegionProsser, Jessica Carlene; Department of Biological SciencesPlant diseases associated with viral infections are a serious issue for growers, causing significant reductions in yield and plant death. Rapid Prunus Decline (RPD) is an emerging disorder resulting in rapid and unexplained death of Prunus species in southern Ontario. In order to better understand RPD, disease symptoms in all major Prunus species in the Niagara region were surveyed, along with identification of major viruses in diseased Prunus trees. Our survey showed that diseased trees often showed symptoms of dehydration, leaf chlorosis, reduced new growth, and death. The average mortality rate in the Niagara region was 20% among all Prunus species with the highest site-specific mortality rate of 67%. In order to understand the contribution of viruses to RPD, RNA sequencing was employed to identify viruses in diseased trees and characterize viral sequence diversity. In total, 20 unique virus species and one viroid were identified in 42 diseased trees, demonstrating a wide diversity of viruses in diseased Prunus trees. Tomato ringspot virus (ToRSV) infection can result in similar symptoms to those observed in RPD trees. Based on these similar symptoms, a total of 507 Prunus trees were surveyed and the frequency of ToRSV infection was determined to be 13%. No direct correlation was identified between the presence of ToRSV and incidence of RPD, suggesting that other factors are involved. Multiple ilarviruses were identified in diseased trees including Grapevine associated ilarvirus (GaIV), Tobacco streak virus (TSV), Tomato necrotic spot virus (ToNSV), Prunus necrotic ringspot virus (PNRSV), and Prune dwarf virus (PDV). GaIV and ToNSV have never been previously reported in Prunus trees, or in Canada. GaIV was the most commonly detected virus and is an emerging concern for stone fruit production. Mixed infection of ilarviruses could have synergistic pathological effects, and the interactions between ilarviruses and other viruses are poorly understood. In summary, over the course of this study, many different viruses were identified in Prunus species exhibiting decline, yet no single virus was identified in all Prunus spp. or in all instances of the disease, suggesting RPD is a complex disease that could have multiple contributing factors.Item Open Access Evaluating and targeting mitochondrial dynamics and plasticity in conditions of mitochondrial dysfunctionBagshaw, Olivia Rita Marie; Department of Biological SciencesMitochondria represent dynamic structures which undergo various changes in morphology in order to rapidly respond to changes in cellular physiology. Changes in mitochondrial dynamics are observed in various pathological events and represent a potential target for therapeutics. In this thesis, I first investigated the role of zinc supplementation on rat aortic endothelial (RAENDO) and smooth muscle (RASMC) cell mitochondrial form and function to elucidate the underlying mechanisms by which zinc prevents the development of smooth muscle neointimal hyperplasia in vivo. I discovered that zinc differentially alters the gene expression of several mitochondria-associated genes in cells treated with ZnSO4 for 7 days. In agreement with this, an increase in mitochondrial network fragmentation (fission) is observed in RAENDO cells, whereas fusion is observed in RASMC cells with zinc treatment. I determined that cell-type specific differences in zinc storage and buffer capacity necessitating different mitochondrial quality control mechanisms may underscore differential responses to zinc exposure in vivo. These results highlight mitochondria as an important target for the treatment or prevention of neointimal hyperplasia in vivo. The potential to modulate mitochondrial network morphology to alter cellular function lead to the second study of this thesis, in which a mitochondrial-targeting moiety, triphenylphosphonium (TPP), is employed to target mitochondrial lipid composition. Here, I evaluated the use of TPP-linoleic acid (TPP-LA) to modulate mitochondrial cardiolipin (CL) composition in a tafazzin knockout (TAZKO) mouse myoblast model of Barth syndrome, a disease characterized by abnormal CL composition. My results indicate that TPP-LA non-significantly enhances mitochondrial membrane potential and apparent fusion in TAZKO and isogenic wildtype (WT) cells. CL analyses reveal that TPP-LA administration for 14 days during differentiation may rescue the CL profile of TAZKO cells. TPP-LA treatment also enhances biochemical differentiation in WT cells but fails to rescue differentiation in TAZKO cells. These results highlight the complex relationship between mitochondrial lipid composition and modulation of mitochondrial dynamics. Taken together, these two projects highlight the plastic nature of mitochondria, their role in pathological conditions and potential as therapeutic targets.Item Open Access AN EXAMINATION OF NOTCH SIGNALLING IN THE REGENERATING SPINAL CORD OF THE AXOLOTL, Ambystoma mexicanum: ESTABLISHMENT AND CHARACTERIZATION OF AN AXOLOTL OPTOGENETIC CONSTRUCT FOR UPREGULATION OF NOTCH1 SIGNALLING IN VIVO.Lee, Jacob; Department of Biological SciencesThe Notch signalling pathway is a juxtacrine signalling pathway conserved across vertebrate and invertebrate species and is known to be a potent regulator of progenitor cell fate decisions during nervous system development. The dysregulation of the Notch pathway has been implicated in the establishment of an anti-neurogenic environment following spinal cord injury in mammals that ultimately prevents functional recovery. In regeneration-competent species, where both neurons and glia are produced by resident progenitor cells in response to trauma, Notch appears to be regulated differently. In the regeneration-competent axolotl, very little is known regarding the role of the Notch signalling pathway in the establishment of a regeneration permissive environment. Here I report that the axolotl possesses a homolog of the Notch1 receptor and qPCR data indicate that its expression decreases significantly at 7 days post injury in caudal spinal cord tissue. I further report that the Notch downstream target gene, Hes1, is expressed in the spinal cord 3 days following injury and that bath application of the indirect Notch inhibitor, tert-Butyl (S)-{(2S)-2-[2-(3,5 difluorophenyl)acetamido]propanamido} phenylacetate (DAPT), impairs spinal cord regeneration. Finally, I have modified an existing optogenetic plasmid construct that allows for light-dependent temporal and spatial Notch receptor-independent signalling through the axolotl Notch intracellular domain (NICD). In vitro characterization has included the determination of an effective membrane anchor for this construct and the production of an appropriate light-insensitive negative control plasmid. This research has provided evidence for a role of Notch during spinal cord regeneration in the axolotl and provided a unique optogenetic tool to facilitate the determination of the in vivo role that Notch signalling plays during spinal cord regeneration in the axolotl.