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Date Permissions Signed

12-20-2016

Date of Award

Fall 2016

Document Type

Masters Thesis

Degree Name

Master of Science (MS)

Department

Biology

First Advisor

Young, Jeff C. (Jeffery C.)

Second Advisor

Brodhagen, Marion (Marion L.)

Third Advisor

O'Neil, Gregory (Gregory W.)

Abstract

Aspergillus flavus is a saprophytic, mycotoxigenic fungus that contaminates agriculturally important seeds with the potently toxic and carcinogenic secondary metabolite, aflatoxin. Seed infection by fungi is often prevented by intact seed coats. Although Arabidopsis thaliana is naturally resistant to Aspergillus infection, certain mutants in the flavonoid biosynthetic pathway are compromised in seed coat integrity. We hypothesized that these mutants might also permit Aspergillus infection. To that end, we systematically tested infectibility of mutants in the flavonoid biosynthetic pathway to identify those lacking resistance to Aspergillus fungal infection. Susceptible seeds included those mutated in the genes encoding for synthesis of the first flavonoid pathway precursor, chalcone, through leucocyanidin (CHS, F3’H, and DFR), indicating that the requisite compound is either leucocyanidin or a derivative of that compound. While preliminary observations suggested that older chs seeds might be more susceptible to A. nidulans than younger seeds, an experiment testing infectibility of seeds harvested at specific ages failed to reproduce the infection rates previously observed. Further investigation revealed that chs seed batches dominated by non-viable seeds are more infectible, as expected from a saprophytic fungus. A novel finding was that chs seeds formed during the final weeks of the parent plant’s development are more highly susceptible to A. nidulans. Our results suggest that wildtype Arabidopsis seeds have a barrier to infection, which may be either mechanical or chemical.

Type

Text

Publisher

Western Washington University

OCLC Number

971049704

Digital Format

application/pdf

Genre/Form

Academic thesis

Language

English

Language Code

eng

Rights

Copying of this thesis in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this thesis for commercial purposes, or for financial gain, shall not be allowed without the author's written permission.

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