DR. LEIGH MCGAUGHEY The Great River Rapport: A collaborative approach to assessing and communicating the ecological health of the Upper St. Lawrence River Born out of the question “What is the health of the St. Lawrence River?” the River Institute, in partnership with the Mohawk Council of Akwesasne, initiated an ecosystem health report on the river. Framed in the Ohén:ton Karihwatéhkwen (Words that come before all else), the project is a science-based, ecosystem health report informed by community-driven research questions. The Great River Rapport engages Indigenous partners, community members and groups, academics, students, and government agencies to produce scientific findings, and translate science into compelling stories and formats that motivate action. It also performs the role of identifying data gaps for future research. Through a participatory approach, a suite of 35 ecological indicators have been selected to reflect the health of the river system. Progress on the project to date will be shared, along with key findings from a selection of the fish indicators (see www.riverrapport.ca). Assistant Professor and Canada Research Chair in Plant Cell Biology Department of Cell and Systems Biology, University of Toronto Building the plant cell wall from the inside out The plant cell wall is a polysaccharide-based extracellular matrix that surrounds and protects all plant cells. Since plants are constantly growing and developing within the confines of their cell walls, plant cells must be in constant communication with their cell walls. Furthermore, cell walls are a critical line of defense between plant cells and their environment; changes to the cell wall are often early warning signs of pathogen attack or abiotic stress, and plants fortify their cell walls in response to these stresses. This ongoing communication between the plant cells and their cell walls is collectively called “cell wall signaling”. The McFarlane Lab at The University of Toronto studies the molecular mechanisms of cell wall signaling and responses, including cell wall secretion and remodeling. We have recently characterized two different pathways that affect cell wall matrix polysaccharide synthesis at the Golgi apparatus. Interestingly, these cell wall synthesis defects result in changes to Golgi structure and function including inappropriate cell wall synthesis, secretion, and/or remodelling. These cellular phenotypes ultimately result in defects in coordinated cell growth and loss of tissue integrity, resulting in dramatic consequences for plant growth and development
University of Rochester The evolutionary history of Drosophila simulans Y chromosomes reveals molecular signatures of resistance to sex ratio meiotic drive The recent evolutionary history of the Y chromosome in Drosophila simulans, a worldwide species of Afrotropical origin, is closely linked to that of X-linked meiotic drivers (Paris system). The spread of the Paris drivers in natural populations has elicited the selection of drive resistant Y chromosomes. To infer the evolutionary history of the Y chromosome in relation to the Paris drive, we sequenced 21 iso-Y lines, each carrying a Y chromosome from a different location. Among them, 13 lines carry a Y chromosome that is able to counteract the effect of the drivers. Despite their very different geographical origins, all sensitive Y’s are highly similar, suggesting that they share a recent common ancestor. The resistant Y chromosomes are more divergent and segregate in 4 distinct clusters. The phylogeny of the Y chromosome confirms that the resistant lineage predates the emergence of Paris drive. The ancestry of the resistant lineage is further supported by the examination of Y-linked sequences in the sister species of D. simulans, D. sechellia and D. mauritiana. We also characterized the variation in repeat content among Y chromosomes and identified two simple satellites ((AAACAAT)n and (AATGG)n) associated with resistance. Altogether, the molecular polymorphism allows us to infer the demographic and evolutionary history of the Y chromosome and provides new insights on the genetic basis of resistance.
Conner Elliot PhD Student, Tufts lab Biotelemetry provides new insights about the migration of adult walleye in Lake Ontario Walleye (Sander vitreus) populations throughout the Laurentian Great Lakes complete annual migrations between spawning and foraging habitats. Until recently, information regarding these migrations was collected using fisheries-dependent data, which can be biased based on fishing effort. Advances in tracking technology and electronic tagging techniques now provide the tools to collect fisheries-independent information about highly mobile species. This thesis examined the timing, extent, and patterns of migration for adult walleye that spawn in the Bay of Quinte and migrate through eastern Lake Ontario. The within-individual repeatability of these annual migrations was determined to be high at the temporal, spatial, and combined spatiotemporal levels. Tagging fish with a combination of acoustic transmitters and pop-off data storage tags (pDSTs) provided insights into the benefits and limitations of each method and identified a novel diving behaviour for this species. Combining the data from both methods provided an overview of the seasonal temperatures, depths, and activity levels experienced by these fish across an entire annual migration. There were sex-based differences in the timing, extent, area use, and vertical activity rates during the annual migration, as well as the number of dives per day during the summer. For most studies, acoustic transmitters can provide estimates of thermal and depth preferences, but they also have important limitations that were identified in this study. This thesis improves our understanding of migratory behaviour in freshwater fish, and the degree to which they are able to repeat these behaviours. It outlines the benefits and limitations of new methods that can be used to collect high-resolution data throughout the year. Future studies should examine the drivers behind these movements, and the mechanisms that these fish use to navigate across large inland waterbodies.
Dr. Molly Stanely University of Vermont Chacterizing a unique subset of taste cells in Drosophila melanogaster All animals must continually make important feeding decisions. Chemosensory neural circuits, such as those for taste and smell, play a key role in directing feeding behaviors. The sensing of food chemicals by specialized sensory taste cells (gustation) helps animals evaluate potential food sources to encourage consumption of nutritive compounds while avoiding potentially harmful compounds. While the cellular and molecular mechanisms for encoding some taste modalities are relatively well-understood, such as ‘sweet’ and ‘bitter’, other taste modalities are more complex, such as ‘salty’ and ‘umami’. The fruit fly, Drosophila melanogaster, offers unparalleled genetic tools to answer neurobiological questions and I have recently used this model organism to help uncover the molecular and cellular mechanisms of salt taste and feeding. While creating a comprehensive map of taste cells on the fly labellum for this project, a unique subset of chemosensory cells with an unknown function were identified. In this seminar, I will share recent work that aims to characterize the activation profile of these taste cells and understand the functional impact of these sensory cells on feeding behaviors.
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