Watalabbe Gamaralalage, Duleeka Indeewaree Gunawardana (2024) Effect of environmental factors and polyketide synthase gene expression in an usnic acid producing lichen-fungus, Cladonia uncialis in its natural habitat and under controlled laboratory conditions. Doctoral (PhD) thesis, Memorial University of Newfoundland.
Full text not available from this repository.
Abstract
One of the most studied lichen secondary metabolites is usnic acid, which is thought to be linked to harsh environmental conditions and potentially mediated by methylphloracetophenone synthase (mpas) and methylphloracetophenone oxidase (mpao) genes in Cladonia uncialis. Chapter 2 examined the relationship between neighboring lichen species composition and soil pH, soil moisture content associated with C. uncialis in three locations in Newfoundland. Results showed that abundance of C. uncialis, C. stellaris, and C. arbuscula correlated with the soil pH, and Cetraria islandica, C. arbuscula, and C. boryi correlated with the soil moisture content. As this study showed that moisture and pH correlated with the ground cover of C. uncialis, these environmental factors were further examined to test their influence on usnic acid production and gene expression (Chapter 3). Results showed that correlation of percent ground cover of C. uncialis, and significant mpao upregulation by soil pH. Since mpas gene expression did not correlate to soil pH under natural habitat, only mpao, in Chapter 4, I tested the effect of pH and temperature on mpas and mpao gene expression and usnic acid production in C. uncialis under controlled laboratory conditions. Results showed a significant effect of pH levels on usnic acid production and a significant effect of temperature on mpas and mpao upregulation. Both gene expression changes were consistently observed in the second week, while usnic acid was detected in high concentrations only after eight weeks of experiments. Based on these results, chapter 5 investigated mpas and mpao activation with UV-B light, which is known to trigger the usnic acid biosynthesis in lichen fungi. Results showed that UV-B light significantly impacted the upregulation of both mpas and mpao genes. Since the overall experiment was based on only C. uncialis lichen fungi, chapter 6 screened mpas activity in a wide range of lichen species, including usnic acid-producing and non-usnic acid-producing lichen species. Results suggested that species that produce usnic acid showed higher mpas activation, providing evidence to support that mpas is responsible for usnic acid production in lichen fungi other than in C. uncialis. These findings warrant further investigation of usnic acid biosynthesis and advance understanding of the regulation of genes involved in this process.
| Item Type: | Thesis (Doctoral (PhD)) |
|---|---|
| URI: | http://research.library.mun.ca/id/eprint/16588 |
| Item ID: | 16588 |
| Additional Information: | Includes bibliographical references -- Restricted until August 12, 2025 |
| Keywords: | lichen diversity, soil pH, secondary metabolites, gene expression, LC-MS/MS |
| Department(s): | Science, Faculty of > Biology |
| Date: | March 2024 |
| Date Type: | Submission |
| Library of Congress Subject Heading: | Lichens--Newfoundland and Labrador; Lichens--Soils; Metabolites; Fungi--Genetics; Cladonia; Gene expression; Biosynthesis; Soil chemistry--Newfoundland and Labrador |
Actions (login required)
 |
View Item |
