Author ORCID Identifier:
Date of Graduation
5-2026
Document Type
Thesis
Degree Name
Master of Science in Plant Pathology (MS)
Degree Level
Graduate
Department
Plant Pathology
Advisor/Mentor
Egan, Martin
Committee Member
Lewis, Jeffery
Second Committee Member
Kud, Joanna
Keywords
Adaptation; Climate change; Filamentous fungus; Heat shock; Magnaporthe oryzae; Microscopy
Abstract
In the face of our rapidly changing global climate, it is essential to understand how rising temperatures will alter the existing threats to global food security. Microbial communities may be forced to adapt and migrate in order to persist in this new climate. These changes will potentially alter the range and control measures growers implement to combat the losses caused by phytopathogens. Magnaporthe oryzae, the causal agent of rice blast disease, is responsible for massive yield losses in rice production across the world. Growers are constantly looking for new control options to spare their rice fields, and it is important to understand how climate change may alter this battle. We took a two-tier approach to analyze how M. oryzae adapts in the face of elevated temperatures. In order to combat the cellular damage caused by heat, all cells, regardless of species, exhibit a heat shock response. When this is activated, heat shock proteins flood the cells to mitigate and remedy the damage. Here we analyze the cellular movements and effects of Hsp104, a heat shock protein and molecular disaggregase unique to fungi. We have found Hsp104 is important for the resumption of polarized growth and regular cellular activities following extreme stress in the hyphae. It takes part in nucleolar rejuvenation and may help to promote mitotic fidelity and nuclear migration following heat stress. Additionally, stress caused by these elevated temperatures have the potential to induce genetic mutations. We used this method to develop a series of thermotolerant mutants in order to dive deeper into the genetic adaptations and phenotypes associated with elevated temperatures. From this series the mutant exhibiting the most robust thermotolerance was subjected to full genome sequencing. This revealed two mutations, one affecting an unnamed CCCH zinc finger and SMR domain-containing protein, and one influencing the transcription factor, stuA, known for its association with stress-related genes. Using this information, and the series of mutants we explore growth rate, sporulation, and pathogenicity levels associated with these genes and the thermotolerant phenotype.
Citation
Broussard, B. K. (2026). Investigating the cellular and genetic adaptation to temperature stress in the model filamentous fungus Magnaporthe oryzae. Graduate Theses and Dissertations Retrieved from https://scholarworks.uark.edu/etd/6115
