Theses and Dissertations

Issuing Body

Mississippi State University

Advisor

Diehl, Susan

Committee Member

Perkins, Andy D.

Committee Member

Prewitt, M. Lynn

Committee Member

Nicholas, Darrel D.

Committee Member

Peterson, Daniel G.

Date of Degree

12-9-2011

Document Type

Dissertation - Open Access

Major

Forest Resources

Degree Name

Doctor of Philosophy

College

College of Forest Resources

Department

Department of Sustainable Bioproducts

Abstract

Brown rot fungi are notoriously copper-tolerant, which makes them difficult to control with copper-based wood preservatives. Brown rot fungi are also unique because they have evolved a bilateral strategy for decay. Their initial attack involves the production of hydroxyl free radicals to increase wood porosity, followed by an enzymatic onslaught of glycoside hydrolases that free the sugars locked within cellulose and hemicellulose. Our molecular understanding of these biological processes, however, has been hampered by our limited knowledge of the underlying genetic mechanisms. To address this knowledge gap, high-throughput, short-read sequencing was used to conduct a comprehensive analysis of the genomics and transcriptomics of wood decay and copper tolerance in the brown rot fungus Fibroporia radiculosa. The results were impressively informative. In the genomic study, the sequences of 9262 genes were predicted and gene function was assigned to 5407 of the genes. An examination of target motifs showed that 1213 of the genes encoded products with extracellular functions. By mining these genomic annotations, 187 genes were identified with putative roles in lignocellulose degradation and copper tolerance. The transcriptomic study quantified gene expression of the fungus growing on wood treated with a copper-based preservative. At day 31, the fungus was adapting to the preservative, and the wood showed no strength loss. At day 154, the preservative effects were gone, and the fungus was actively degrading the wood, which exhibited 52% strength loss. A total of 917 differentially expressed genes were identified, 108 of which appeared to be regulating wood decay and preservative tolerance. Genes that showed increased expression at day 31 were involved in oxalate metabolism, hydroxyl free radical production by the enzyme laccase, energy production, xenobiotic detoxification, copper resistance, stress response, and pectin degradation. Genes that exhibited higher expression at day 154 were involved in wood polysaccharide degradation, hexose transport, oxalate catabolism, catabolism of laccase substrates, proton reduction, re-modeling the glucan sheath, and shoring up the plasma membrane for acid shock. These newly discovered genes represent a significant step towards accelerating a genome-wide understanding of brown rot decay and tolerance to wood preservatives.

URI

https://hdl.handle.net/11668/16224

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