Spontaneous mutagenesis can be divided into three main steps: the introduction of DNA
damage and lesions, damage recognition and DNA repair. All sources of spontaneous
mutagenesis originate from within the cell itself, e.g., polymerase errors cause DNA
mismatches and reactive oxygen species alter the chemical composition of DNA bases. The
combined effects of all these processes influence spontaneous genomic mutation rates, which
are thought to be a characteristic of individual species and/or groups of species. Although
much is known about different mutagens and how they cause mutations the sequence context
of these mutations are less well understood. The results of this MSc study on mutation in the
filamentous fungus Fusarium circinatum showed that the 5ʹ and 3ʹ neighbouring bases of a
single nucleotide polymorphism can significantly influence the type of substitution that
occurred leading to the formation of mutational motifs. This was the case for both sets of
genes examined (core housekeeping and non-ribosomal protein synthetase genes), whose
evolution is known to differ. The fact that none of the identified motifs are shared between
the two sets of genes could indicate that the cellular mutagens and/or repair machinery
function differently for the two gene groups. Furthermore, none of the mutable motifs that
have been identified for the well-known mutagens in model organisms could be detected in
the fungus, which suggests that mutagens and/or DNA repair mechanisms of this fungus are
unique. Although limited information is available for non-model eukaryotes, an estimate for
the rate at which mutations arise across the genome of F. circinatum could be a good starting
point for comparisons of its evolutionary rate to those of its close relatives. This was
accomplished using a fluctuation analysis involving nitrate non-utilizing mutation reversion.
Although mutation rate determined in this study is probably not precisely accurate, it
represents a good starting point for future comparative studies on the evolutionary rate of
Fusarium species. As a whole this study laid the foundation for a better understanding of
spontaneous mutagenesis at specific sites in certain groups of genes as well as across the
genome of the economically important plant pathogen F. circinatum.
Restricted until August 2017 / Dissertation (MSc)--University of Pretoria, 2013. / gm2013 / Microbiology and Plant Pathology / Unrestricted
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:up/oai:repository.up.ac.za:2263/32988 |
| Date | January 2013 |
| Creators | Van Coller, Sophia Johanna |
| Contributors | Steenkamp, Emma Theodora, Fourie, G., Wingfield, Brenda D. |
| Publisher | University of Pretoria |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Dissertation |
| Rights | © 2013 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. |
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