Date of Graduation

12-2014

Document Type

Thesis

Degree Name

Master of Science in Plant Pathology (MS)

Degree Level

Graduate

Department

Plant Pathology

Advisor

Burton H. Bluhm

Committee Member

Kenneth L. Korth

Second Committee Member

James C. Correll

Third Committee Member

Ines Pinto

Keywords

Conidiation, Fumonisin, Fusarium ear rot, Fusarium verticillioides, Pathogenicity

Abstract

Filamentous fungi are responsible for numerous plant and animal diseases. The filamentous ascomycete Fusarium verticillioides is a globally important pathogen of maize, capable of causing severe yield reductions and economic losses. Also of substantial concern is the contamination of infected kernels with fumonisins, toxic secondary metabolites linked to toxicoses in humans and livestock. The number of sequenced fungal genomes is rapidly increasing. However, functional characterization of fungal genes has not progressed at a comparable rate. In pathogenic fungi, uncharacterized genes represent a source for novel virulence factors or anti-fungal targets. Therefore, to fully understand the genetic mechanisms underlying fungal pathogenesis, characterizing genes with no known function is important. In this work, a novel gene provisionally named FUG1 (Fungal Unknown Gene 1) was characterized in F. verticillioides via molecular genetics. Despite broad conservation among phylogenetically diverse groups of fungi, putative FUG1 orthologs have not been studied and have no known or predicted biological function. Targeted deletion of FUG1 in F. verticillioides resulted in a pleiotropic phenotype, including reduced radial growth and suppression of asexual reproduction. Importantly, deletion of FUG1 impaired colonization of maize kernels and reduced fumonisin accumulation in the kernel environment. The deletion strain was more sensitive to hydrogen peroxide and the antimicrobial compound, 2-benzoxazolinone (BOA), which provided evidence that FUG1 may have an important role in responding to mechanisms of host defense. Transcriptional profiling revealed that numerous categories of genes are differentially expressed in the kernel environment following deletion of FUG1, including genes involved in carbohydrate metabolism and oxidation-reduction processes. Moreover, deletion of FUG1 in the related pathogen Fusarium graminearum resulted in reduced colonization of maize silks and wheat heads, suggesting that FUG1 may have a conserved role in fungal pathogenesis. Taken together, these results implicate FUG1 in growth, development, and pathogenesis in two Fusarium spp. Additionally, this work illustrates the importance of characterizing unknown genes in filamentous fungi and supports the idea that uncharacterized genes represent a source for potential anti-fungal targets.

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