<p>Fungi display
diverse growth forms. Some grow as unicellular yeasts, some grow as
multicellular hyphae, while others switch between these two growth forms, i.e.,
the dimorphic fungi. Dimorphism is found in many pathogenic fungi, and it is
thought to be a strategy to maximize their fitness during different stages of
life cycles. The corn smut fungus <i>Ustilago maydis</i> serves as a renowned
model organism for studying fungal dimorphism and its role in pathogenesis. However, knowledge
only from the model species may not be expanded to other species unless
multispecies studies have been demonstrated. In this dissertation, I performed
comparative analyses to examine if knowledge from <i>U. maydis</i> is
translational to other dimorphic fungi. First, a physiological study was
conducted to find what can serve as a common signal for dimorphic transition of
several Ustilaginomycotina species. I found that the lipid serves as a potential
common cue for yeast-to-hyphal transition in most dimorphic species, while alternate
types of energy-source carbohydrate do not affect fungal dimorphism. In
addition, pectin and high temperature can also trigger filamentous growth in
some Ustilaginomycotina species. Second, I performed comparative
transcriptomics to determine if a mechanism for yeast-to-hyphal dimorphic
transition is conserved across multiple dimorphic species. Three species of
Ustilaginomycotina (<i>U. maydis</i>, <i>Tilletiopsis washingtonensis </i>and <i>Meira
miltonrushii</i>) plus one species from Ascomycota (<i>Ophiostoma novo-ulmi</i>)
were included in the analyses. I found that the similarity of transcriptomic
alteration is not dependent on phylogenetic relatedness. Genes in amino acid transport
and metabolism, energy production and conversion and cytoskeleton are commonly
altered during the dimorphic transition of all studied species. Moreover, I
discovered several core genes which can play a conserved role in transducing
signals for the dimorphic transition. Finally, I performed comparative analyses
of 190 fungal genomes to determine genomic properties that are associated with
types of fungal growth form. I found that small genome size is a characteristic
for yeast-like fungi. Few indicator genes, such as genes encoding proteins in
the NADPH oxidase complex and cytoskeletons, which are predominantly lost in
yeast-like fungi in both Ascomycota and Basidiomycota. However, many other
genes are associated with types of growth form in a lineage-specific manner. Findings
from this dissertation will serve as fundamentals for future research in fungal
cell biology, especially in fungal dimorphism. Additionally, results from this
study suggest cautions when extrapolating results from model species onto non-model
species.</p>
| Identifer | oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/10381979 |
| Date | 20 November 2019 |
| Creators | Teeratas Kijpornyongpan (7887371) |
| Source Sets | Purdue University |
| Detected Language | English |
| Type | Text, Thesis |
| Rights | CC BY 4.0 |
| Relation | https://figshare.com/articles/Comparative_Studies_of_Fungal_Dimorphism_in_Dikarya/10381979 |
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