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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Application of antimicrobial peptides to control leaf rust (Puccinia triticina) infection in bread wheat (Triticum aestivum L.)
(Lethbridge, Alta. : University of Lethbridge, Dept. of Biological Sciences, 2024) Panthi, Urbashi; University of Lethbridge. Faculty of Arts and Science; Kovalchuk, Igor; Bilichak, Andriy
Screening and developing novel antifungal agents with minimal environmental impact are needed to maintain and increase crop production constantly threatened by various pathogens. Small peptides with antimicrobial and antifungal activities have been known to play an important role in plant defense both at the pathogen level by suppressing its growth and proliferation as well as at the host’s level through activation or priming of the plant’s immune system for faster, more robust response against fungi. Rust fungi (Pucciniales) are plant pathogens that can infect key crops, threaten global food security and are capable of overcoming the resistance genes introduced in elite wheat cultivars. We performed an in vitro screening of 19 peptides predominantly of plant origin with antifungal or antimicrobial activity for their ability to inhibit leaf rust (Puccinia triticina, CCDS isolate) urediniospores germination. Nine peptides demonstrated significant fungicidal properties compared to the control. Foliar application of the top three candidates, β-purothionin, Purothionin-α2 and Defensin-2, decreased the severity of the leaf rust infection in wheat (Triticum aestivum L.) seedlings. Additionally, increased pathogen resistance was paralleled by elevated expression of the defense-related genes.
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Multigenerational UV stress effects in Arabidopsis thaliana offspring
(Lethbridge, Alta. : University of Lethbridge, Dept. of Biological Sciences, 2024) Lopez Virgen, Andres Guadalupe; University of Lethbridge. Faculty of Arts and Science; Kovalchuk, Igor
Continuous exposure to environmental stress contributes to species diversity and drives microevolutionary processes. However, whether epigenetic alterations, such as differential DNA methylation, are prerequisites for speciation events remains unclear. We hypothesized that prolonged stress exposure would increase epigenetic diversity more than genetic diversity. In this study, we analysed the effects of 25 consecutive generations of UV-C stress on the genome and epigenome of Arabidopsis thaliana. Our results showed that multigenerational UV-C exposure led to significant genetic and epigenetic changes in the progeny. Genomic analysis of the UV-stressed progeny (F25UV) revealed a higher frequency of genetic variations compared to controls (F25C, F2C), with deletions being more prevalent than insertions, probably due to the mechanisms of DNA damage and repair processes triggered by UV radiation. F25UV also exhibited a significantly higher proportion of nonsense mutations, with C-to-T transitions being the most common, likely due to deamination of methylated cytosines. Epigenomic analysis showed that F25UV plants had more differentially methylated cytosines (DMCs) across all contexts than the F2C group. F25UV also had more DMCs than the F25C group in the CHG and CHH contexts, with the most striking difference in the CHH context, where F25UV had over 10-fold more DMCs than the F25C group. Despite these genetic and epigenetic changes, no differences in progeny resilience under stress were observed, based on root analysis, reactive oxygen species levels, and overall growth at both the seedling and mature stages. Our findings suggest that UV radiation stress can induce genetic and epigenetic changes that are capable of being inherited in transgenerational manner. Although these changes did not result in more resilient plants, their non-random nature suggests an evolutionary and adaptive direction.
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Leading professional learning: comparative perceptions of teachers and school leaders
(Lethbridge, Alta. : University of Lethbridge, Faculty of Education, 2025) Good, Brandon; Adams, Pamela; Wood, Kevin
A comparison of responses from teachers and school leaders is used to assess the effectiveness of various leadership strategies in facilitating teacher professional learning. Analysis used t-tests at a 95% confidence level to determine significant differences between the responses of the two groups. Results about effectiveness of strategies used by school leaders show agreement between the teachers and school leaders, and confirm existing research about their efficacy. However, results about the frequency that school leaders use these strategies show statistically significant differences between teachers and school leaders’ experiences of their use. These strategies include the use of school leader/teacher collaboration on professional learning, professional learning that is directly applicable to a teachers’ classroom, and the use of inquiry in the learning process. Additionally, significant differences were reported in the frequency with which school leaders observe teachers teach.
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Oxidative stress damages rRNA inside the ribosome and differentially affects the catalytic center
(Oxford Academic, 2018) Willi, Jessica A.; Küpfer, Pascal; Evéquoz, Damien; Fernandez, Guillermo; Katz, Assaf; Leumann, Christian; Polacek, Norbert
Intracellular levels of reactive oxygen species (ROS) increase as a consequence of oxidative stress and represent a major source of damage to biomolecules. Due to its high cellular abundance RNA is more frequently the target for oxidative damage than DNA. Nevertheless the functional consequences of damage on stable RNA are poorly understood. Using a genome-wide approach, based on 8-oxo-guanosine immunoprecipitation, we present evidence that the most abundant non-coding RNA in a cell, the ribosomal RNA (rRNA), is target for oxidative nucleobase damage by ROS. Subjecting ribosomes to oxidative stress, we demonstrate that oxidized 23S rRNA inhibits the ribosome during protein biosynthesis. Placing single oxidized nucleobases at specific position within the ribosome's catalytic center by atomic mutagenesis resulted in markedly different functional outcomes. While some active site nucleobases tolerated oxidative damage well, oxidation at others had detrimental effects on protein synthesis by inhibiting different sub-steps of the ribosomal elongation cycle. Our data provide molecular insight into the biological consequences of RNA oxidation in one of the most central cellular enzymes and reveal mechanistic insight on the role of individual active site nucleobases during translation.
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Dynamic 23S rRNA modification ho5C2501 benefits Escherichia coli under oxidative stress
(Oxford Academic, 2021) Fasnacht, Michel; Gallo, Stefano; Sharma, Puneet; Himmelstob, Maximilian; Limbach, Patrick A.; Willi, Jessica A.; Polacek, Norbert
Post-transcriptional modifications are added to ribosomal RNAs (rRNAs) to govern ribosome biogenesis and to fine-tune protein biosynthesis. In Escherichia coli and related bacteria, RlhA uniquely catalyzes formation of a 5-hydroxycytidine (ho5C) at position 2501 of 23S rRNA. However, the molecular and biological functions as well as the regulation of ho5C2501 modification remain unclear. We measured growth curves with the modification-deficient ΔrlhA strain and quantified the extent of the modification during different conditions by mass spectrometry and reverse transcription. The levels of ho5C2501 in E. coli ribosomes turned out to be highly dynamic and growth phase-dependent, with the most effective hydroxylation yields observed in the stationary phase. We demonstrated a direct effect of ho5C2501 on translation efficiencies in vitro and in vivo. High ho5C2501 levels reduced protein biosynthesis which however turned out to be beneficial for E. coli for adapting to oxidative stress. This functional advantage was small under optimal conditions or during heat or cold shock, but becomes pronounced in the presence of hydrogen peroxide. Taken together, these data provided first functional insights into the role of this unique 23S rRNA modification for ribosome functions and bacterial growth under oxidative stress.