Dr. Ivan Oresnik Department of Microbiology, University of Manitoba Relationship between central carbon metabolism and nitrogen fixation in Sinorhizobium meliloti Carbon metabolism is generally well understood in Sinorhizobium meliloti. The literature is consistent with the role of dicarboxylic acid metabolism while the bacteroid is actively fixing nitrogen. However, the literature contains many nitrogen fixation phenotypes ascribed to mutants that encode enzymes in central carbon metabolism that make little sense, or are even paradoxical. For example, a mutation in pckA, which is necessary for gluconeogenesis and encodes phosphoenolpyruvate carboxy kinase, consistently gives nitrogen fixation rates that are approximately 50% of wild-type, yet no measurable enzyme activity can be detected in bacteroids. Similarly, our work has shown strains that do not have triose phosphate isomerase activity also yield plants with 50% dry matter accumulation when grown under nitrogen deficient conditions. To date there is no clear explanation why these lesions affect nitrogen fixation based on our current knowledge. Based on our observations, we are hypothesizing that carbon metabolism may be correlated with endoreplication during bacteroid development and that rates of nitrogen fixation may be linked to the copy number of genes directly involved in nitrogen fixation. Although this may explain what occurs in indeterminate nodules, it probably does not apply to determinate nodules, suggesting that what limits nitrogen fixation between these nodule types may be different. Lisa Han MSc, Yakimowski Lab Estimating the stability and heritability of resistance fueling copy number variation in glyphosate-resistant Amaranthus palmeri Copy number variation (CNV), especially when present in extrachromosomal fashion, provides unparalleled opportunity for speciation and adaptation. As observed in agricultural weed species, Amaranthus palmeri, CNV of the herbicide glyphosate’s target gene, EPSPS, has resulted in emergence of glyphosate-tolerant and resistant populations across the globe. The amplification of EPSPS copies in forms of extrachromosomal circular DNA (eccDNA) poses unique challenges when assessing the heritability of EPSPS CNV as its origin and the tethering mechanisms are still mostly unknown. I used 30 F0 pairs and 900 F1 individuals from glyphosate-resistant populations to examine the heritability of EPSPS CNV in relation to parental EPSPS CNV. The results display a shifting pattern in progeny CNV with increasing parental mean EPSPS copy number. Over 70% of progeny resulting from parental crosses of low-med CNV displayed an increase in EPSPS CNV in a single generation while the opposite pattern was observed in progeny resulting from high EPSPS CNV mean parental crosses. This result indicates a substantial decline in heritability after a threshold point of 48.8 mean parental EPSPS CNV. The weaker heritability of eccDNA gene copy number variation at high CNV suggests weak evolutionary potential of highly glyphosate resistant CNV individuals and may constrain the evolution of population EPSPS CNV mean.
Dr. Megan Bontrager Department of Ecology & Evolutionary Biology at University of Toronto Local adaptation at range edges and under anomalous climates Species’ geographic ranges are limited on the landscape. A major focus of work in the Bontrager lab is identifying which evolutionary and ecological forces interact to shape species’ geographic distributions and limit adaptation. In addition, populations are frequently adapted to their local environments, and my lab works to identify which components of the environment are the most important factors driving local adaptation. I will talk about how gene flow affects range edge populations and how these effects may be especially important under climate change. I will also present results from two quantitative syntheses of transplant experiments to 1) examine how climate change is altering patterns of local adaptation, 2) evaluate the relative importance of temperature and precipitation to local adaptation and 3) examine how the magnitude of local adaptation changes from range centres to range edges. This work explores critical drivers of plant population performance and characterizes patterns of adaptation across species' ranges.
Regan Cross PhD, Eckert Lab Long-term experimental analysis of ecological and evolutionary processes at a species’ range limit Why do species have stable range limits – and what happens if they break free? Many species’ geographic ranges have historically been stable in space, but they may shift as climate change alters habitats. My thesis first looks at why species have stable range limits; what prevents them from dispersing beyond their ranges and adapting to the new habitat? I briefly review the current state of the field of range limits and provide a novel long-term test of whether a species’ range is limited by its niche. Next, I examine a few things that might happen if species shift their ranges using a beyond-range transplant experiment with the best coastal dune plant, Camissoniopsis cheiranthifolia. First, I ask: are populations from the range center or edge better suited to establish in beyond-range habitat? And second: did populations adapt to beyond-range conditions over ten generations? Finally, I test whether local or genetically mixed populations perform best within the range, to inform conservation efforts to re-establish populations and restore habitats. Come to my talk to learn about the mechanisms stopping species from expanding their ranges, some of the ecological and evolutionary processes going on during range shifts, and which populations are best used for conservation efforts like assisted migration and habitat restoration! (The photo is me with my first flowering transplant in 2018.)
Bryan Hau MSc, Snedden Lab Investigating the interaction of Arabidopsis calmodulin-like (CML) proteins with calmodulin-binding transcription activators (CAMTAs) Understanding the how organisms detect and interpret information from their environment is an ongoing goal in cell biology. A common theme among eukaryotic cells is the use of calcium ions (Ca2+) as second messengers during information processing. In plants, Ca2+ signals are evoked during responses to abiotic and biotic stresses and during development. These signals are detected by Ca2+-binding proteins (sensors), such as the evolutionarily-conserved protein calmodulin (CaM), which regulates various downstream target proteins to organize signal transduction pathways. In addition to CaM, plants have evolved a remarkable array of CaM-like proteins (CMLs) that are not found in animals. The genetic model, Arabidopsis, has seven CaMs and 50 CMLs, most of which remain unstudied. Why do plants need so many of these Ca2+ sensors? What are their downstream targets? How do they contribute to Ca2+ signaling during stimulus response? Research on CML structure/function is needed to develop a broader understanding of how plants respond to environmental cues. Recently, our lab has been exploring the roles of two paralogs, CML13,14, which possess unique biochemical properties among CaMs and CMLs. To help uncover CML13,14 function, we screened a yeast 2-hybrid library for putative target proteins and discovered 3 families of functionally unrelated proteins that share a common structural feature; tandem IQ domains. IQs are unique CaM binding domains that have been mainly studied in the myosin motor proteins of animals. In addition to myosins, we identified several CaM-binding transcription activators (CAMTAs) as putative CML13,14 targets. CAMTAs possess multiple IQ domains and are important transcription factors in plants that regulate gene expression during abiotic and biotic stresses such as cold, drought, salt stress, pathogen attack, and herbivory. I will present data from my MSc project where I explored the question; are Arabidopsis CAMTAs targets of CML13,14? My project focused mainly on assessing the properties of CML13/14-CAMTA binding, using both in planta and in vitro methods. Using a genetic approach, I also discovered a key role in salinity stress response for CML13. Collectively, my data supports the hypothesis that CAMTAs and CMLs interact in plants and suggests a novel mechanism through which Ca2+ signals regulate gene expression during stress response.
Dr. Anusha Shankar Lab of Ornithology at Cornell University Hot and cold hummingbirds: The ecology, physiology and genes of cold endotherms Information about Dr. Anusha Shankar here
Hummingbirds live fast. They have among the highest metabolic rates of all vertebrates, and must eat constantly to stay alive. I will talk about some of what I have learned about how they manage their energy budgets during the day, and how they allocate time and energy to different activities based on changes in their environment. At night, they save energy by entering the fascinating hibernation-like state of torpor. How do they manage to get so cold (~50°F/10°C) and slow their metabolism down as much as they do, and stay alive? This is what I am currently working on finding out. My work integrates methods and approaches from ecology, physiology and transcriptomics to understand how these tiny endotherms manage to survive in a variety of environmental conditions. Kapillesh Balasubramaniam MSc, Smol Lab Assessing the impacts of emerging anthropogenic stressors on lakes within the Rideau Canal system: A paleolimnological re-assessment Earlier diatom-based paleolimnological studies were conducted on a suite of diverse lakes (i.e., Lower Rideau L., Big Rideau L., Otter L., Upper Rideau L., Indian L., L. Opinicon) within the Rideau Canal system ~25-30 years ago and provided important information regarding the ecological impacts of canal construction (1827-1832). Following these early paleolimnological studies, the same lakes are now facing the potential impacts of newly emerging environmental stressors, particularly accelerated climate warming. Here, I revisited the same suite of lakes by conducting a series of paleolimnological analyses, focusing on recent changes in diatom assemblage composition, to assess the potential ecological impacts of newly emerging environmental stressors. Despite the substantial environmental impacts associated with canal construction, the highest rate of diatom compositional change across the suite of lakes only took place in the past ~25-30 years, which coincided mainly with an increase in planktonic diatom taxa. This recent shift in assemblage composition could not be explained by nutrient enrichment, as total phosphorus (TP) concentrations, measured since the 1980s, have significantly declined across the study lakes. The continued increase of planktonic taxa across the study lakes suggests the impact invasive zebra (ca. 1990) mussels in the Rideau Canal region appeared to have only been modest. Rather, these recent changes in diatom assemblage composition were strongly related to increasing regional air temperatures, as the conditions associated with warmer temperatures (i.e., longer, and stronger periods of thermal stratification, alterations to water-column mixing regimes, reduced ice cover duration) provide favorable conditions for extensive planktonic diatom growth. Lakes within the Rideau Canal system are changing rapidly in ecologically significant ways and will likely continue to do so as temperatures continue to rise.
Zoe Lai MSc Candidate, Regan Lab Exploring the cellular basis of environmental stress and plant development: Bioremediation potential of Senna and gene function in Populus As of 2021, the earth holds about 3.04 trillion trees. Plants account for 80% of the world’s total biomass. Trees, and plants in general, inherently play very important roles in our daily lives. My thesis examines the potential of a plant, Senna occidentalis, to phytoremediate arsenic- and cadmium-contaminated soils. Additionally, my thesis advances our understanding of leaf and stem development though the analysis of a mutant line of Populus tremula x Populus alba called shriveled leaf.
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