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Feldman, Erin Christie

University of British Columbia

As the most recently diverged mycorrhizal lineage, ericoid mycorrhizal (ErM) fungi remain facultatively symbiotic and have retained many saprotrophic enzymes. This symbiosis represents an adaptation to acidic and nutrient-poor soils that plants in the Ericaceae family typically inhabit, including tundra, boreal forests, heathlands and peatlands – environments whose carbon sequestration capabilities are particularly sensitive to changing climate. The majority of soil carbon is derived from plant or fungal biomass; one way to examine the role of soil fungi in carbon cycling is to examine their ability to break down cell wall material contained within these soils. To investigate the saprotrophic potential of the ErM fungus Oidiodendron maius, I used two complimentary techniques. First, RNA sequencing was used to examine differential expression of cell wall degrading enzymes (CWDEs) by O. maius across substrates of different carbon complexity: glucose, bovine serum albumin and peat. I found significant differential regulation of 52 CWDEs in response to substrate, 13 of which were selected as targets for quantification across a greater number of substrates. I then performed droplet digital PCR (ddPCR)-based transcript abundance profiling of these target CWDEs in O. maius grown on 11 carbon sources of varying complexity. Concurrently, I developed a method to validate reference gene selection to generate normalization factors, calculated as the geometric mean of three reference gene transcript levels . After normalization, the coefficient of variation between biological replicates was substantially reduced, though by varying degrees dependent on the target gene assayed. While differential regulation of these transcripts was not as pronounced as I had predicted, I was able to demonstrate a significant upregulation of several transcripts responsible for cellulose and hemicellulose degradation in response to peat- and cellulose-containing substrates. Overall, this thesis represents the first of its kind to employ ddPCR to quantify transcript abundance in O. maius. The results from my studies demonstrate the potential of O. maius to degrade a wide range of lignocellulosic substrates and provide fundamental understanding regarding the enzymes responsible for this decomposition. A more comprehensive analysis of ErM fungal degradation capabilities will provide a deeper understanding of carbon sequestration and release within vulnerable ecosystems.

Text

2021-08-20

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/79361

Biology

University of British Columbia

UBCO

http://creativecommons.org/licenses/by-nc-nd/4.0/