OPUS: Open Ulethbridge Scholarship
Open ULeth Scholarship (OPUS) is the University of Lethbridge's open access research repository. It contains a collection of materials related to research and teaching produced by the academic community.
Self-archiving your research in OPUS is one way to meet Open Access policies of granting agencies. It is important to retain your final, post-peer-reviewed drafts for submission to OPUS, as this is often the only version publishers will allow to be archived. Click here for information on the U of L Open Access Policy.
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Item
Ovule defects in Arabidopsis thaliana PIN localization pathway mutants lead to reduced seed set
(Lethbridge, Alta. : University of Lethbridge, Dept. of Biological Sciences, 2025) Reiter, Jaxon W.; University of Lethbridge. Faculty of Arts and Science; Schultz, Elizabeth
Chapter 1:
Auxin is a plant hormone that is essential for a wide range of growth and developmental processes in plants. The coordinated, polar transport of auxin through plant tissues is crucial for proper development and function. The asymmetric localization of PIN-FORMED (PIN) proteins determines the directionality of auxin transport between cells and across a tissue, creating an auxin gradient that can influence gene expression and development. It is well known that auxin gradient establishment is vital for vegetative development, including leaf and root formation, but the involvement of auxin in reproductive development is less-well studied. The plasma-membrane localization of PIN proteins to direct auxin transport between cells is a critical process that involves a complex vesicle transport pathway and is regulated by a diverse set of genes. This review provides an overview of the current state of knowledge regarding the roles of PIN proteins during the development of the reproductive structures of a flower, the gynoecium and androecium, and describes some of the genes that have been proposed to function in this PIN localization pathway. Mainly, the importance of PIN1 localization and PIN1-mediated auxin transport for the development of the gynoecium, including the carpel tissue, ovary, ovules, and female gametophyte, is described in detail, emphasizing the importance of these processes during reproductive development in plants.
Chapter 2:
The formation of the gynoecium, including the stigma, style, transmitting tract, ovary, ovules, and female gametophytes requires the correct establishment of auxin gradients across a tissue directed by polar transport. PIN-FORMED (PIN) proteins are crucial for establishing local cellular auxin gradients that establish spatially organized auxin maxima and minima. PIN1 vesicle transport is tightly regulated by various genes that play a role in vesicle formation, transport, uncoating, and membrane localization. SCARFACE/VASCULAR NETWORK DEFECTIVE 3 (SFC/VAN3), FORKED1 (FKD1) & FORKED-LIKE (FL) Group 1 genes, COTYLEDON VASCULAR PATTERN 2 (CVP2) and CVP2-LIKE 1 (CVL1), PINOID (PID), and ROTUNDA3 (RON3) have all been proposed to be key players in the regulation of PIN1 vesicle trafficking. Mutations to these genes have been shown to disrupt PIN1 localization and lead to developmental defects such as impaired root development and vein formation. However, the role of these genes has not been previously characterized in gynoecium development, despite mutants showing severe reductions to seed set. This study examines the underlying causes of the seed set reductions present in fkd1/fl1-2/fl2/fl3, sfc-40, and cvp2/cvl1 mutants by analyzing reproductive development. Through manual pollination experiments, observation of pollen tube growth, and the analysis of ovule defects and pPIN1:PIN1-GFP expression during ovule development, I identified that reduced seed set in these mutants results from a gynoecium defect. Specifically, a reduced seed set involves altered ovule development, and I suggest that the observed morphological defects are consistent with alterations to PIN1 localization during early ovule development stages (2 ii-iii) in these mutants. This study suggests, for the first time, that SFC, FKD1, FL1, FL2, FL3, CVP2, and CVL1 play an important role in reproduction during ovule development.
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Explicit zero density for the Riemann zeta function
(Lethbridge, Alta. : University of Lethbridge, Dept. of Mathematics and Computer Science, 2024) Farzanfard, Golnoush; University of Lethbridge. Faculty of Arts and Science; Fiori, Andrew
[See thesis for abstract]
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Modelling air, ground surface, and permafrost temperature variability across four dissimilar valleys, Yukon, Canada
(Canadian Science Publishing, 2024) Garibaldi, Madeleine C.; Bonnaventure, Philip; Noad, Nick C.; Kochtitzky, Will
Spatial maps of the air and ground thermal regime were generated for four Yukon valleys. The aim was to model air, ground surface, and ground temperature (at fine spatial resolution) using locally measured inverted surface lapse rates (SLR) to better predict temperature along an elevation gradient. These local models were then compared to a regional permafrost probability model, which utilized differing inversion assumptions, as well as circumpolar and national models generated without considering inversions. Overall, permafrost probability in the regional model matched well with the local models where assumptions of treeline and inverted SLRs held true. When normal SLRs were assumed, permafrost presence was overestimated in each valley. This discrepancy was greatest at high elevations where permafrost was predicted to be the coldest and most widespread. However, the difference between valleys was dependent on surface and subsurface characteristics such as higher snow cover, mature forest, or thick organic layers which show a greater disassociation from the air temperature overall. Appropriate characterization of the SLR is essential for accurate predictions of the ground thermal regime’s spatial distribution and permafrost presence. These models also provide a starting point for better predictions of warming in these valleys and other areas subject to inversions of similar magnitudes.
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Modelling permafrost distribution using the temperature at top of permafrost model in the boreal forest environment of Whatì, NT
(Canadian Science Publishing, 2024) Vegter, Scott; Bonnaventure, Philip; Daly, Seamus; Kochtitzky, Will
Current permafrost models in Canadian boreal forests are generally of low spatial resolution as they cover regional or continental scales. This study aims to understand the viability of creating a temperature at the top of permafrost (TTOP) model on a local scale in the boreal wetland environment of Whatì, Northwest Territories from short-term field-collected temperature data. The model utilizes independent variables of vegetation, topographic position index, and elevation, with the dependent variables being ground surface temperature collected from 60 ground temperature nodes and 1.5 m air temperature collected from 10 temperature stations. In doing this, the study investigates the relationship vegetation and disturbance have on ground temperature and permafrost distribution. The model predicts that 31% of the ground is underlain by permafrost, based on a mean annual temperature at TTOP of <0 °C. This model shows an accuracy of 62.5% when compared to cryotic assessment sites (CAS). Most inaccuracies, showing the limitations of the TTOP model, came from peat plateaus that had been burned in the most recent forest fire in 2014. These resulted in out-of-equilibrium permafrost and climatic conditions that TTOP cannot handle well. Commonly, permafrost mapping places Whatì in the extensive discontinuous zone, estimating that between 50% and 90% of the ground is underlain by permafrost. The study shows that a climatically driven TTOP model calibrated with CAS can be used to illustrate ground temperature heterogeneity from short-term data in boreal forest wetland environments. However, this approach likely underestimates permafrost extent and is perhaps not the best-suited modelling choice for near-surface permafrost, which is currently out of equilibrium with the current climate.
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Rock glacier inventory and predictive modeling in the Mackenzie Mountains: predicting rock glacier likelihood with a generalized additive model
(Canadian Science Publishing, 2024) Thiessen, Rabecca; Bonnaventure, Philip; Lapalme, Caitlin M.
Rock glaciers have been the subject of extensive research in recent years due to their potential to serve as indicators of past and present climate conditions and their potential impacts on water resources. Location and descriptive rock glacier data within the Mackenzie Mountains were used to build a rock glacier inventory that will serve as a valuable resource for future research and monitoring efforts. Additionally, this study maps the likelihood of rock glacier presence using extracted variables in a generalized additive model (GAM). The model incorporates attribute data, including potential incoming solar radiation (PISR), topographic position index (TPI), slope, elevation, and lithology as controls for rock glacier development. Topographic data were compiled for three study regions of the Mackenzie Mountains from a 30 m digital elevation model (DEM). The analysis of the GAM showed that the most significant explanatory variables were PISR, elevation, slope, and TPI. The GAM model had an accuracy of 0.87 with a sensitivity of 0.92. This study provides important insights into the controls, distribution, and dynamics of rock glaciers in the Mackenzie Mountains, as well as both the limitations and the potential of statistical models in predicting their occurrence.