Biological Sciences Undergraduate Works

Permanent URI for this collectionhttp://hdl.handle.net/1993/37761

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Access status: Open Access ,
Antibody Validation as a tool to study “Synaptic Adhesion Proteins”
(2026-03) Ameena, Nabiha; Stacey, Joy (Biological Sciences); Siddiqui, Tabrez; Balci, Fuat
Historically there has been an absence of reliable and validated antibodies against synaptic adhesion proteins, particularly neurexins and neuroligins. This has led to the failure of the vital experiments that study the function of these synaptic proteins, leading to wastage of time and expensive resources. My project validated antibodies against neurexins and neuroligins through the process of immunoprecipitation, which pulls the protein of interest, followed by the process of western blot to visualize the results. The results indicated that the antibodies against β isoforms across the three neurexins performed better. Similarly, antibodies against Nlgn 2 and Nlgn 3 showed consistent bands congruent with the molecular weight of neuroligin. This project also investigated the role of Nrxn1γ, an isoform of neurexin1, in maintaining the excitatory-inhibitory balance between synapses that is required for optimal synaptic function. Collectively, these findings not only establish a dependable set of antibodies for probing neurexin and neuroligin biology but also underscore Nrxn1γ as a meaningful contributor to inhibitory synapse maintenance, strengthening both the technical and conceptual foundations for future synaptic research.
Access status: Open Access ,
Discovery of Antibacterial Compounds from Medicinal Plant Endophytes
(2026-04) Kwiatkowski, Nadia; Kumar, Ayush (Medical Microbiology and Infectious Diseases); Lee, Jae-Hyeok (Biological Sciences); Whyard, Steve; Hausner, Georg
Antimicrobial resistance is an escalating global health threat that necessitates the discovery of new bioactive compounds. Fungal endophytes, which live asymptomatically within plant tissues, are increasingly recognized as promising sources of novel secondary metabolites with antimicrobial activity. In this study, fungal endophytes were isolated from seven medicinal plant species and screened for antibacterial activity against clinically relevant bacterial pathogens. A total of 264 morphologically distinct fungal endophytes were isolated from surface-sterilized root and leaf tissues. Initial antibacterial screening identified 58 isolates (22%) capable of inhibiting the sensitive Acinetobacter baumannii strain AB258. Antibacterial isolates were disproportionately derived from root tissues (74.1%), suggesting that roots represent a particularly rich source of bioactive endophytes. Of these active isolates, 24 demonstrated broader-spectrum activity against additional bacterial strains. Fifteen isolates producing the strongest inhibition zones were selected for crude extract preparation and secondary screening using disc diffusion assays against a bacterial panel including methicillin-resistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosa, and Acinetobacter spp. Several extracts exhibited multi-strain inhibitory activity, with isolates DL16, GB29, and GB2 producing the largest zones of inhibition. Three candidate isolates (GB2, LV6, and DL16) were prioritized for chemical investigation. Thin-layer chromatography revealed distinct metabolite profiles, with GB2 displaying the greatest compound separation. Consequently, GB2 was selected for further purification using flash chromatography, yielding three pure fractions. Minimum inhibitory concentration (MIC) assays of these fractions revealed relatively high MIC values (128–256 μg mL⁻¹) across tested strains, indicating limited antibacterial potency of individual compounds but suggesting potential synergistic interactions among metabolites. Overall, this study highlights the diversity of fungal endophytes associated with medicinal plants and demonstrates their potential as sources of antibacterial metabolites. These findings support continued exploration of plant-associated fungi for novel antimicrobial compound discovery.
Access status: Open Access ,
Effects of wounding and salinity stress on faba bean (Vicia faba): role of salicylic acid in plant defense responses
(2026-04) Tahir, Aysha; Zelmer, Carla (Biological Sciences); Lee, Jae-Hyeok (Biological Sciences); Renault, Sylvie
Plants are often exposed to multiple stress factors at the same time, and one stress can influence how a plant responds to another. While salinity and mechanical wounding are both known to affect plant growth and physiology, their combined effects, and the role of salicylic acid (SA), are not well understood in Faba bean (Vicia faba). In this study, Faba bean (Vicia faba cv. Broad Windsor) plants were exposed to salinity (150 mM NaCl), mechanical wounding, and foliar application of SA (0.5 mM) in different combinations. Several physiological, biochemical, and growth parameters were measured, including chlorophyll fluorescence (Fv/Fm), stomatal conductance, transpiration, biomass, water content, protein content, chlorophyll levels, and leaf elemental composition. Salinity had the strongest effect on the plants as it significantly reduced stomatal conductance, transpiration, and shoot biomass, while increasing the accumulation of Na, Cl, and N in the leaves. Fv/Fm values remained relatively stable, suggesting that photosystem II was not severely affected. An unexpected infection by Colletotrichum sp. caused high levels of necrosis in control plants, while salt-treated plants showed less injury. Chlorophyll and protein levels were higher in salt-treated plants, likely because these plants had less fungal damage. Wounding had only minor effects overall, with small changes in water content and shoot biomass, and slightly lower levels of necrosis. Salicylic acid did not have a significant effect on most measured parameters. Overall, these results show that salinity was the main factor affecting plant responses and may also provide indirect protection against pathogen infection. This study highlights the importance of considering multiple stresses and unexpected factors, such as pathogen presence, when studying plant stress responses.
Access status: Open Access ,
Invasion overlap: Abundance, diet, and interactions of two co-occurring invasive crabs (Carcinus maenas and Hemigrapsus sanguineus) in Nova Scotia, Canada
(2026-04) Mader, Lauren; Docker, Margaret (Biological Sciences); Davoren, Gail (Biological Sciences); Ramey-Balci, Patricia
Ecosystems increasingly harbour multiple invasive species, which can alter ecological interactions that influence their establishment, spread, and impacts on native communities. The recent arrival of the Asian shore crab to Atlantic Canada, where the European green crab has been well-established since the 1950s, provides an opportunity to examine how these invasive species interact during the initial stage of co-invasion in their newly shared range. This study examined their spatial co-occurrence and relative abundance at two sites in Nova Scotia during the summers (July/August) of 2022–2025 (quadrat sampling), along with diet analyses (stomach content) in 2022 and 2023. Follow-up experiments determined whether feeding and diet are altered by the presence of a competitor (alone vs. inter/intra-specific pairings). Both species were found in areas of <0.25 m2. Green crabs were significantly more abundant than shore crabs (a single exception in 2025), indicating that the shore crab is still in the early stage of invasion. Both species are omnivorous generalists, consuming a variety of shared food items (12 species/taxa); however, the relative proportions of food items in crab stomachs differed between species and locations. Animal prey was predominant in green crab stomachs, whereas shore crabs contained a relatively high proportion of macroalgae. Similarly, green crabs were more likely to consume animal prey than macroalgae and vice versa for shore crabs. Green crabs altered their diet in the presence of shore crabs such that when paired with a shore crab, they were equally likely to consume either food item, but when alone or paired with a conspecific, they were more likely to consume barnacles. In contrast, shore crabs did not alter their diet in the presence of green crabs. These results are important for understanding how interactions among invasive species influence feeding and resource use, with implications for population and community dynamics.
Access status: Open Access ,
Timing and nest aggression in Purple Martins (Progne subis)
(2026-03) Klassen, Sara; Davoren, Gail (Biological Sciences); Waterman, Jane (Biological Sciences); Fraser, Kevin
Earlier arrival at the breeding grounds after migration can confer advantages for migratory songbirds, including access to higher food abundance and to better compete for desirable territories. Selection for one sex to arrive before the other is often due to intrasexual competition for territories and mates, though the link between early female arrival (protogyny) and female-female competition is unclear from lack of research on female territoriality and nest aggression. I explored timing and aggression in the cavity nesting species Purple Martin (Progne subis), where males are known to defend nest cavities and compete aggressively toward other males though display protogyny, but these patterns have not been investigated in females. I investigated whether early arrival timing has selected for higher levels of aggression, competition for territory, and nest defense between females. I conducted a behavioural experiment at nesting colonies of Purple Martin in Winnipeg, Manitoba, where levels of aggression were assessed with simulated territorial intrusion using taxidermy mounts of female martins. I found that early nesting and age were positively associated with aggression, affirming that older birds that arrive and nest earlier are likely more experienced and in better condition to defend cavities. Sex had no significant effect on aggression, suggesting shared duty of defending nests by both members of the social pair regardless of the sex of the intruder. Females defended most aggressively after eggs were laid, which supports the parental investment hypothesis, where higher aggression is associated with higher nest investment. Overall, this study provides new insight on the role of age and timing on female aggression and nest defense in a migratory songbird, which will be valuable to further explore as migration timing advances with climate change.
Access status: Open Access ,
Application timing and environmental conditions influence the effects of humic and fulvic acid on growth, yield, and cold stress response in spring wheat (Triticum aestivum)
(2026-04) Fischer, Sabrina; Renault, Sylvie (Biological Sciences); Lee, Jae-Hyeok (Biological Sciences); Belmonte, Mark
Humic and fulvic acid-based biostimulants are increasingly used in agriculture to enhance plant physiological processes, improve crop performance, and, more recently, help tolerate abiotic stressors. Despite their widespread use, the optimal timing of application for greatest benefit remains poorly understood. Additionally, few studies have assessed the effects of organic acids on plants under low-temperature stress. This study examined the effects of humic and fulvic acid applications at different growth stages on physiological parameters, including photosynthetic metrics and plant nutrient levels, as well as agronomic measures in spring wheat (Triticum aestivum L.). A second objective was to study the effects of a humic acid seed treatment on wheat development and gene expression under low-temperature stress. The results revealed that the physiological responses to fulvic or humic acid application differed by growth stage, environmental conditions, and application timing. Fulvic acid applied during vegetative growth (wheat Zadok stage 25-37) resulted in the greatest yield increase of 9%, corresponding to 347 kg/ha of wheat, in small-plot randomized field trials. Wheat seeds treated with humic acid and subjected to low-temperature stress showed improved developmental characteristics, with cold-responsive gene expression varying by gene target and treatment. Taken together, these findings show that physiological traits and grain yield are strongly dependent on the timing of humic and fulvic acid application, with the greatest yield response occurring during early vegetative growth. Furthermore, humic acid can improve early developmental growth characteristics of wheat under low-temperature conditions, but specific gene expression should be further studied.
Access status: Open Access ,
Human Land Use Impacts on Native Plant Genetic Diversity
(2026-04) Ferris, John; Worley, Anne (Biological Sciences); Markham, John (Biological Sciences); Garroway, Colin
Extensive research has been conducted to determine how urbanization and human land use affect the genetic diversity and population structure of animal populations. Plant populations experience many direct and indirect effects of human activities, such as habitat fragmentation, the introduction of invasive species and herbivores, and declines in pollinators. Despite awareness that urbanization and agriculture are the largest threats to plants globally, very little research has directly assessed this relationship on a broad scale. To examine this, I compiled a list of 2745 terrestrial plant species endemic to North America from the IUCN and then conducted a programmatic search of the Dryad Digital Repository for microsatellite genetic datasets for these species. Upon manual review of these datasets, 15 appropriate datasets with georeferencing were selected for usage in this study. The final database comprised 7535 individuals of 427 populations of 21 species. I estimated gene diversity, rarefied allelic richness, and population-specific FST for each site and used these values as response variables in a series of Bayesian Hierarchical Generalized Linear Mixed Models (GLMMs) to test relationships between population genetic composition and human land use. I treated species as a random effect with random slopes and intercepts. This allowed me to observe species-specific trends in the data. My results indicated that across 21 species, populations in areas with high rates of human land use exhibit greater population differentiation and higher overall genetic diversity. In contrast, areas with high human population density showed overall increases in genetic diversity and decreased population differentiation. My results show clear, albeit weak, trends, suggesting that the small sample size and lack of diversity in life history traits were limitations.
Access status: Open Access ,
Exploring L1 syndrome-causing L1CAM as a trans-synaptic modulator of mGluR5
(2026-04) Cameron, Sarah; Marcoliese, Paul (Biochemistry and Medical Genetics); Stacey, Joy (Biological Sciences); Dunn, Henry; Xing, Lei
Neurotransmission typically occurs when neurotransmitters, released by the presynapse, interact with receptors on the postsynapse. Interruptions in these interactions can lead to neurological disorders. Recently, these trans-synaptic interactions were found to involve synaptic adhesion molecules, modulating the activity of a subgroup of G protein-coupled receptors (GPCRs) known as the metabotropic glutamate receptors (mGluRs). A synaptic adhesion molecule called L1CAM has been found to interact with mGluR5. L1CAM is of particular interest because it is the known cause of L1 syndrome, a neurodevelopmental disorder that can cause hydrocephalus, spastic paraplegia, and intellectual disability. As a well-established drug target for neurological disorders, mGluR5, in complex with L1CAM, may have major implications in the etiology of L1 syndrome. We hypothesize that L1CAM is a trans-synaptic modulator of mGluR5. Co-immunoprecipitation experiments were conducted to detect binding of L1CAM, the synaptic adhesion molecule, to the receptors, mGluR5 and mGluR2 (a negative control), at the protein level. Trans-cellular signaling experiments were conducted to determine the functional response of the L1CAM-mGluR interaction at the cellular level. As a result, we found that L1CAM does complex with mGluR5 and not mGluR2. A functional response has not yet been seen, but it is possible that different experimental conditions are required to accurately reflect cell conditions in vivo. In future research, discovery of L1CAM-mGluR5 trans-cellular modulation would lead to further understanding of trans-synaptic interactions between mGluRs and synaptic adhesion molecules, and possibly further the understanding of the etiology of L1 syndrome. As an overarching objective of possible L1CAM-mGluR5 modulation, a therapeutic could be developed to rescue the interaction of L1CAM and mGluR5 in those with L1 syndrome.
Access status: Open Access ,
Characterizing drought response strategies in diverse Asian rice varieties
(2026-04) Edel, Jaimie; Garroway, Colin (Biological Sciences); Campbell, Kevin (Biological Sciences); Wilkins, Olivia
Drought events are being exacerbated by climate change and result in the reduced growth, yield, and survival of crops. Rice, a staple crop in the diets of nearly half of the global population, is a semi-aquatic plant that is extremely sensitive to drought. However, the natural and artificial selection of rice across varying ecological regions and climates worldwide has resulted in the adaptation of different cultivated varieties (cultivars) of rice to diverse environmental conditions, leading to variable drought resistance capabilities and differential investments into distinct drought response strategies, such as increased root growth or early maturation, across cultivars. These response strategies can be largely grouped into three categories: drought tolerance, drought avoidance, and drought escape. Rice drought response, however, is a complex, multigenic trait involving many converging molecular pathways that regulate plant structure and function. As a result, much about the coordinated internal networks controlling rice drought responses remains unknown. In this study, growth and gas exchange parameters were compared across 17 regionally distinct Asian rice (Oryza sativa) cultivars grown in either well-watered (3 g H2O/g dry soil) or growth-limiting drought (1 g H2O/g dry soil) soil conditions to screen for drought response. The chlorophyll content and relative transcript abundance of target genes (OsABA2, OsADF3, OsIAA6) in the leaf tissue were additionally assessed in two identified drought-resistant cultivars (Bala, Krasnodarskij 424) relative to a drought- sensitive common reference cultivar for rice (Nipponbare). Altogether, these data were used to investigate whether geographically diverse rice cultivars invested in reducing the effects of drought stress on the plant through distinct pathways, where differences were expected to indicate specific drought response strategies characteristic of that cultivar. Bala and Krasnodarskij 424 had diverse morphological and functional drought responses, with differences in water use, leaf developmental timing, biomass, and transcript abundance for genes OsADF3 and OsIAA6. These differences suggest that Krasnodarskij 424 may use drought avoidance strategies, while Bala may use both drought avoidance and drought escape strategies. This study aims to supplement ongoing research into the identification of agronomically beneficial drought response strategies, assisting in the targeted development of climate change-resilient crops.
Access status: Open Access ,
The impact of thermal stress on the gene expression, plasma lactate, osmolality, and growth of juvenile bull trout (Salvelinus confluentus)
(2026-04) Bennett, Raven; Stacey, Joy (Biological Sciences); Anderson, Gary (Biological Sciences); Jeffries, Ken; Mochnacz, Neil
Bull trout (Salvelinus confluentus) is a cold-water stenotherm that occupies a cold thermal niche relative to many freshwater fishes in North America. Consequently, populations at the southern range extent have been impacted by warming streams and many are listed as Threatened; however, it is unclear if populations further north will respond similarly. This study investigates the effects of thermal stress on gene expression, plasma lactate, osmolality, and growth in juvenile bull trout from a source population in Smith-Dorrien Creek, Alberta. One-year-old bull trout were acclimated to three ecologically-relevant temperatures (9°C, 15°C, and 21°C) for 60 days. Transcript abundance of genes involved in heat stress, growth-metabolism, immune response, and ion transport were measured as cellular stress indicators in gill and liver tissues using high-throughput qPCR, while plasma lactate and osmolality were assessed as physiological stress indicators. Osmolality and lactate decreased with temperature, suggesting compromised osmoregulatory function at elevated temperatures and an increased reliance on anaerobic metabolism. Condition factor and growth were highest at 9°C, with reduced condition despite continued growth at 15°C; fish held at 21°C exhibited markedly reduced growth, poorer body condition, and the highest mortality after 60 d. Sex had no significant effect on growth or physiological metrics. Gill and liver showed a decreased abundance of genes involved in growth-metabolism, ion transport, and immune function, while abundance of heat stress genes increased. The combined physiological and transcriptional evidence suggests that 15°C represents a sub-lethal stress threshold, while 21°C approaches the upper functional thermal limit for this population.
Access status: Open Access ,
Validation and application of a metagenomics protocol to the root-associated fungal communities of Northern wild rice (Zizania palustris)
(2025-08) Spring, Abby; Markham, John (Biological Sciences); Bakker, Matthew (Microbiology); Klymiuk, Az
The occurrence of root-associated fungi in wetland plants is not yet well-understood, despite recent indications that some contain diverse mycobiomes, including potential plant mutualists. Although arbuscular mycorrhizal fungi (AMF) can be neutral and even parasitic, emerging evidence suggests that AMF provide benefits to many wetland plants, as in terrestrial soils. Dark septate endophytes (DSEs) occur in wetland plants at similar or greater frequencies than AMF and may also confer benefits to host plants. Zizania palustris (Northern wild rice, manômin) is an emergent annual macrophyte found in shallow lakes and slow-moving rivers in central and eastern North America, where it is harvested from both wild stands and cultivated paddies. Despite the significance of this plant to Indigenous peoples and emerging agricultural interests, its fungal diversity in traditional rice lakes or wild stands is currently unknown. To identify the root-associated fungal communities of Z. palustris collected from wild stands across Manitoba and determine its mycorrhizal status, I undertook ITS and 18S targeted amplicon sequencing of the rhizosphere soil and determined the incidence of fungal structures within roots via microscopy. Since wetland soils contain contaminants that inhibit metabarcoding, I optimized DNA extraction and amplification protocols prior to their application to these samples. The ITS data suggested that the rhizosphere is primarily basidiomycotan and ascomycotan. The 18S data identified three genera of AMF available in the surrounding rhizosphere for association with Z. palustris: Glomus, Acaulospora, and Claroideoglomus. The root incidence data showed consistent fungal colonization by aseptate and dematiaceous hyphae, with somewhat lower incidence of hyaline hyphae and AMF-like structures, despite complete inundation of all plants. While confirmation of Z. palustris as a mycorrhizal plant requires sequencing of the root-endogenous fungi, this thesis presents preliminary data confirming the presence of AMF in the rhizosphere and AMF-resembling structures within the roots.
Access status: Open Access ,
Herbivory resistance to generalist feeder Trichoplusia ni of faba bean (Vicia faba) exposed to salinity stress
(2025-03) Lavallée-Shrupka, Caleb; John Markham (Biological Sciences); Kevin Fraser (Biological Sciences); Renault, Sylvie; Avila-Sakar, German
Plants are often exposed to multiple stress factors simultaneously. Exposure to one stress can exacerbate or mitigate the response to a subsequent stress. While salinity and herbivory can impair growth and physiological function individually, their combined effects remain poorly understood. To investigate this interaction and determine if salt tolerance influences resistance to herbivory, Vicia faba (cv. Broad Windsor) plants were grown under salinity (0, 50, 75, 100 mM NaCl) and exposed to cabbage looper (Trichoplusia ni) herbivory. Gas exchange parameters (photosynthesis, stomatal conductance, transpiration) were not significantly affected by salinity after 11 days of treatment. After 20 days, salinity did not affect plant height, stem biomass or water content of most tissues but significantly reduced root and lateral leaf biomass. Total phenolic compounds and total soluble proteins in the leaves were also unchanged. Elemental analysis revealed that salinity significantly increased Na and Cl concentrations in all three tissue types (leaves, stems, and roots), with the highest accumulation in roots. Salinity significantly increased the concentrations of macronutrients (N, P, K, Ca, and Mg) and micronutrients (Fe, Mn, Cu, Zn, and Mo) in the leaves, suggesting efficient nutrient retention in photosynthetically active tissues. Constitutive resistance to herbivory was not significantly affected by salinity. However, induced resistance was significantly impaired in salt-treated plants. Together, these findings indicate that V. faba exhibits moderate tolerance to salinity, maintaining gas exchange and nutrient homeostasis under salt stress while minimizing growth impairments. The compromised induced resistance highlights the vulnerability of inducible defenses and suggests that salinity may force a tradeoff between preserving physiological function and sustaining inducible defences against herbivory. These results emphasize the importance of considering stress interactions when evaluating plant defence.
Access status: Open Access ,
Acute effects of quinoline and 2-methylquinoline on electrical activity of great pond snail (Lymnaea stagnalis) neurons
(2025-04) Tramley, Cameron; Tomy, Gregg (Chemistry); Markham, John (Biological Sciences); Fry, Mark
Polycyclic aromatic compounds (PAC) are organic compounds found ubiquitously in the environment and originate naturally or anthropogenically. They are persistent, bioaccumulative, and toxic (PBT). PACs have been found to modulate voltage gated ion channels in fish cardiomyocytes. Many studies have examined PACs effects, however, there is growing concern about a less studied class of PACs: hetero-polycyclic aromatic compounds (HPACs). Quinoline and its derivative 2-methylquinoline are two-ringed HPACs found in high concentrations in sediment and tissues of fishes from the Great Lakes. Studies investigating synthetic quinoline derivatives used in the pharmaceutical industry have shown HPACs modulate voltage gated sodium, calcium and potassium ion channels in cardiomyocytes of fishes and mollusk neurons. We therefore designed a study investigating the acute neurobiological effects of quinoline and 2-methylquinoline on Great Pond Snail (Lymnaea stagnalis) neurons, a model with a large easily accessible central nervous system and well conserved ion channels. Electrophysiological characteristics were measured by performing suction electrode experiments on the right internal nerve of the right parietal Lymnaea stagnalis ganglion. Extracellular recordings before and after application of various quinoline or 2-methylquinoline concentrations were used to determine the frequency of right parietal nerve activity which we normalized as percent of control. The extracellular recordings revealed that quinoline affects right parietal nerve activity in a dose dependent manner. Quinoline caused a statistically significant effect on right parietal nerve activity at 1000 nM, but not 100 nM, and 10 nM, with mean percent of control values being 89.2 ± 4.3%, 103.9 ± 4.6% and 99.9 ± 3.5% respectively. 2-Methylquinoline had no statistically significant effect on right parietal nerve activity at 1000 nM. These experiments highlight the importance of understanding the neurobiological effect of PBT environmental contaminants quinoline and 2-methylquinoline, as well as demonstrate the utility of suction electrode recordings as an electrophysiology technique to evaluate acute neurotoxicity of environmental contaminants.
Access status: Open Access ,
Evaluating Nitrogen Utilization Strategies in Chlamydomonas reinhardtii
(2025-04) Tibule, Miku; Doering, Jennifer (Biological Sciences); Markham, John (Biological Sciences); Lee, Jae-Hyeok
Nitrogen (N) is a common, yet essential macronutrient required for nucleic acid and amino acid synthesis for cell growth and biomass of photosynthetic eukaryotes which includes algae and plants. Understanding how organisms strategically use N for growth will allow development of economical use of N fertilizer being invested into croplands, which in return mitigates anthropogenic contribution to environmental pollution. This honours thesis explores N-use strategies by examining the N-sensing mechanisms within Chlamydomonas reinhardtii to investigate its necessity for optimal growth under N-limited and N-repleted conditions through comparative growth within individual N source provision of NH4Cl, KNO3, and urea. Using photobioreactor and nitrogen quantification experiments, I obtained biomass productivity data and residual N within the cultures, which allowed for an understanding of algal growth under various N-source concentration conditions. Through a comprehensive data analysis of growth biomass OD and residual N concentrations, my study uncovered that there is a regulatory mechanism of C. reinhardtii that allows for a reduction in N consumption rate under extreme N limitation stress, which in turn allows the algae to shift its metabolic priorities to internal N-use. These insights contribute to the existing literature by highlighting the significance of the N-sensing mechanism within C. reinhardtii, for N-use strategies, discovering a temporal switch in metabolic function, and offering potential further investigations into how the algae prioritize cellular N contents for growth and cellular division. Ultimately, this study provides a deeper understanding of N assimilation and cellular use, paving the way for future research and developments in the field.
Access status: Open Access ,
Regulation of gene expression by growth differentiation factor 15 in the developing mouse and human neocortex
(2025-04) Mohamad, Ruby; Docker, Margaret (Biological Sciences); Lee, Jae-Hyeok (Biological Sciences); Xing, Lei
The evolution of the neocortex, specifically its expansion, is the key advancement that made higher cognitive abilities possible. Humans today have a neocortex that constitutes up to two-thirds of their overall brain mass. This expansion reflects increased and prolonged activity of neural progenitor cells (NPCs), which give birth to neurons during fetal cortical development. Growth differentiation factor 15 (GDF15) is a cell-extrinsic signal that has previously been found to promote basal progenitor proliferation, one of the main classes of NPCs critical to human brain development and evolution. Previously, the Xing Lab discovered several potential downstream targets that could be regulated by GDF15 in the fetal human neocortex, including Dachshund Family Transcription Factor 1 (DACH1), Glypican 6 (GPC6), Semaphorin 5A (SEMA5A), and Shroom Family Member 3 (SHROOM3). All of which have been reported to have various roles in neurodevelopment. In this study, we manipulated GDF15 levels in the developing mouse and human neocortex to understand its regulatory effect on the potential downstream targets. My range-finding experiment indicated a concentration-dependent increase in mRNA levels of the downstream targets, with the most increase observed in fetal human neocortical tissue incubated with 100ng/ml recombinant human GDF15 protein. Knockout of the GDF15 gene in embryonic mice revealed decreased mRNA levels of all the downstream targets. Furthermore, adult GDF15 knockout transgenic mice exhibited a decrease in interneuron and deep-layer neuron numbers. My findings are consistent with the notion that GDF15 regulates NPC proliferation through these downstream targets, contributing to long-term effects on neuron abundance in the adult brain.
Access status: Open Access ,
Measuring the Active Learning Gains of Students In Undergraduate Biology Labs Using Peer Review
(2025-03) Bantel, Joseph; Joy Stacey (Biological Sciences); Tamara Kelly (York University); Debets, Cassandra
The peer-review process allows students to engage in the valuable exercise of critically thinking about how they generate and judge the validity of an idea. This is a cornerstone of the scientific community and a core component of biological sciences. Some students in undergraduate studies routinely underperform in the traditional educational experience and benefit greatly from active learning. In a first-year introductory biological science course at the University of Manitoba, I studied the population by using an online peer-review platform called Peerceptiv to study the standardized learning gains of different demographic groups of students to determine if any subgroups experienced a disproportional benefit in this learning exercise compared to any others. I hypothesized that peer-to-peer feedback on scientific graphing would raise the measurable graded assignment scores of URM students in undergraduate biological science, and therefore predicted that there would be no significant difference between URM and non-URM students' graded performance after peer-to-peer input. Students in certain groups did have higher learning gains over the course of the semester when averaged however, these results were not significantly different from the rest of the population. Overall, the reception of the exercise was very positive in student perceptions with 79% of respondents saying that it helped them understand the concepts they learned about. The strongest response was from students saying that getting reviews of their work was the most useful, with 87%. Ultimately, this study shows that students learn from the peer review process and have learning gains associated with it however, additional testing is necessary to definitively say which groups may or may not benefit the most from this activity.
Access status: Open Access ,
Impacts of a flea beetle double-stranded RNA-based insecticide on the ground beetle Pterostichus melanarius
(2025-04) Lampimaki, Silas; Belmonte, Mark (Biological Sciences); Lee, Jae-Hyeok (Biological Sciences); Whyard, Steve
Flea beetles (Phyllotreta cruciferae and P. striolata) are the most damaging insect pests of canola, one of Canada’s most economically valuable crops. Chemical insecticides are currently the primary method of flea beetle control, but concerns about their impact on non-target organisms highlight the need for safer alternatives. RNA interference (RNAi) has been recognized for its ability to selectively kill insect pests by silencing target genes through sequence-specific exogenous double-stranded RNA (dsRNA). However, sequence similarity between pest and beneficial insects continue to pose risks about potential off-target effects. In this study, two dsRNAs targeting the UBE2L3 and Snf7 gene in P. cruciferae were evaluated for off-target effects in the predatory ground beetle Pterostichus melanarius. A bioinformatic analysis was used to identify the similarity between the dsRNA sequences and their respective orthologs in P. melanarius. Beetles were then injected with the dsRNAs, and relative gene expression and mortality were measured. Following injection of the UBE2L3 dsRNA, which shares 83.4% similarity and a 29 bp matching segment with P. melanarius, target gene expression was reduced by 69.9%. Conversely, injection of the Snf7 dsRNA, which only shares 62.6% similarity, did not induce gene knockdown. Despite the knockdown of UBE2L3, no significant mortality was observed in any treatment group, including the positive control, suggesting that an insufficient dose of dsRNA was used. These findings demonstrate that sequence similarity influences the off-target effects of dsRNA, which can be predicted using a bioinformatic assessment. Continued sequencing of beneficial insects is required so that dsRNA can be designed to have minimal similarity with other species to reduce off-target effects.
Access status: Open Access ,
Investigating the impact of helminths on mercury in Arctic foxes
(2025-04) Whiteside, Kayla; Detwiler, Jillian (Biological Sciences); Davoren, Gail (Biological Sciences); Roth, Jim
Mercury (Hg) pollution in the Arctic poses a growing threat to the health of local wildlife, yet many factors behind Hg bioaccumulation remain poorly understood. Primarily ingested through diet, Hg bioaccumulates in animal tissues and can impair neurological and reproductive functions. Intestinal helminths have demonstrated the ability to take up Hg while residing in their hosts and have consequently been suggested to benefit their hosts through mitigating toxin exposure. In this study, I used Arctic foxes harvested over five years from Churchill, MB to analyze fox muscle total mercury concentrations ([THg]) (ng/g), intestinal helminth [THg], and helminth biomasses to determine if (i) helminth group (taxa and size) influences helminth Hg uptake, and (ii) helminths benefit their host by decreasing host Hg uptake. Results showed that [THg] did not significantly vary with fox sex, age, or harvest year. Cestodes demonstrated higher [THg] than nematodes, though size did not influence [THg] for either taxon. Both cestodes and nematodes demonstrated [THg] increases relative to host [THg], though only the cestodes had significantly higher [THg] than their hosts, and no significant effect was seen for either cestode or nematode biomass on fox [THg]. Overall, this study provides valuable insight into host-helminth-Hg dynamics. Further research is needed to elucidate the mechanisms and significance of helminth Hg uptake to help understand their potential applications in mitigating toxin exposure in wildlife.
Access status: Open Access ,
The effects of topically-applied double-stranded RNA pesticides on Myzus persicae
(2025-03) Joseph, Kelvin Tom; Wilkins, Olivia (Biological Sciences); Lee, Jae-Hyeok (Biological Sciences); Whyard, Steve
The green peach aphid (Myzus persicae) is a major agricultural pest, causing billions in crop losses and contributing to global food insecurity. Increasing incidences of insecticide resistance and off-target effects highlight the need for alternative control methods. RNA interference (RNAi), a gene-silencing mechanism triggered by exogenous double-stranded RNA (dsRNA), has emerged as a promising approach to species-specific pest control. Topically applied dsRNA offers a non-GMO alternative to traditional pesticides, selectively inducing mortality in pests by targeting essential genes. One such gene, Chitin Synthase (CHS), is crucial for the insect exoskeleton, tracheae, and gut. However, dsRNA penetration through the aphid’s hydrophobic exoskeleton remains a challenge, necessitating delivery enhancements like surfactants. This study tested two dsRNA structures—long linear dsRNA (210 bp) and short paperclip RNA (pcRNA, 25 bp)—targeting CHS, with and without the surfactant Silwet. Third-instar aphids were topically treated with a dsRNA droplet, and their survival and fecundity were monitored over eight days. Several bioassay optimizations were implemented, including stretching diet packets, treating third instars instead of adults, filter-sterilizing diets, and chilling aphids before treatment. Bioassays demonstrated that dsRNA + Silwet significantly increased aphid mortality, whereas dsRNA alone and all pcRNA treatments had no significant effects. No significant fecundity reduction or CHS gene knockdown was observed. While only a single gene target was assessed, findings suggest RNAi-based pesticides hold potential for aphid control, and Silwet improves dsRNA efficacy. Further research on optimizing dsRNA formulations could enhance their application as next-generation pesticides.
Access status: Open Access ,
Comparing the boldness and exploration of co-occurring invasive marine crabs (Hemigrapsus sanguineus and Carcinus maenas)
(2024-03) DeJaegher, Emily; Detwiler, Jillian (Biological Sciences); Davoren, Gail (Biological Sciences); Ramey-Balci, Patricia
Boldness (i.e., the propensity to take risks) and exploratory behaviours can influence an animal’s ability to acquire resources, thus affecting competitive success. The Asian shore crab, Hemigrapsus sanguineus, and European green crab, Carcinus maenas, co-occur as highly invasive species in coastal areas of the United States, and more recently, in Atlantic Canada. Both crabs use structurally complex rocky intertidal habitat and consume similar macroalgal and invertebrate prey, such that they likely compete for resources. Competitive interactions between co-invaders could influence the success of either species, affecting their impacts on the ecosystem. Yet, there is a gap in research comparing behaviours, such as boldness or exploration, between co-invaders such as these crabs. Here, the boldness of H. sanguineus and C. maenas are compared by investigating their tendencies to exit preferred rocky habitat with shelter to explore an open and brightly lit area. The crabs’ exploratory tendencies are also compared, by evaluating if the species spontaneously alternate (i.e., preferentially explore regions that they have least recently explored), an indicator of efficient exploration. The two species had similar latencies when exiting the sheltered habitat, but C. maenas spent more time in the open area overall. Both crabs also tended to spontaneously alternate, but H. sanguineus had a greater tendency to do so than C. maenas, revealing for the first time the existence of significant differences in spontaneous alternation behaviour between invasive species. If the strong exploration ability of H. sanguineus can improve the species’ ability to find resources, it may have a competitive advantage over C. maenas in regions where the crabs co-occur.

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