<p> Many fungal species are studied to understand pheromone and receptor interaction associated with mating behavior. An established genetic model for mating in higher fungi is heterothallic <i>Schizophyllum commune </i>. This fungus uses its pheromones to communicate compatibility among mates, typically leading to the production of haploid meiotic basidiospores. <i> S. commune</i> has thousands of mating types, as part of its tetrapolar mating system in which mating is determined by two unlinked complex genetic loci, one of which codes for both mating pheromones and receptors (<i> matB</i>). <i>Schizophyllum umbrinum</i> is a fungal species which was described by Raper (1959) as a homothallic species but has not been studied in depth. <i>S. umbrinum</i> produces viable basidiospores, but has the means to bypass outcrossing. The studies described in this thesis were designed to examine components of a putative <i>S. umbrinum</i> <i> matB</i> locus and possible pheromone communication between the two <i> Schizophyllum</i> species. Two ways we explored <i>S. umbrinum</i>’s reproductive behavior was to look for evidence of functional pheromone genes and pheromones, and to search for variation among progeny and strains collected from different locations that might be indicative of more than one <i> matB</i> type and outcrossing. <i>S. umbrinum</i> <i> matB</i> noncoding regions were examined with PCR for variation among progeny of a wild-collected mushroom. There were no DNA length differences detected among 11 siblings for PCR covering 1.9 kb of amplified DNA and spaced over 11kb in the genome. Using Southern blot analysis, the whole <i> matB</i> coding and noncoding regions between putative pheromone genes <i> suph1</i> and <i>suph9</i> were examined. These results verified and expanded beyond the PCR assay. The results suggest that the mushroom that produced the 11 sibling strains was not produced by outcrossing that involved two different <i>matB</i> idiomorphs but was likely produced from a homothallic mating where no <i>matB</i> mating type idiomorphs exist. The conservation and similarities in amino acid sequences between the predicted mature pheromones of <i>S. commune</i> and <i>S. umbrinum</i> suggested possible function of the <i>S. umbrinum</i> pheromone genes products. Heterologous expression and activity were tested in baker’s yeast, <i>S. cerevisiae</i>, and <i>S. umbrinum </i> genes were also introduced into mushroom <i>S. commune</i>. In the yeast mating assay, successful communication between <i>S. umbrinum </i> pheromone SuPh3 and suph9 was demonstrated. In the <i>S. commune </i> mating assay, successful communication of <i>S. umbrinum</i> pheromones SuPh6, SuPh7, and suph9 with <i>S. commune</i> receptors <i> in vivo</i> was demonstrated. The ability to elicit signal transduction in both heterologous assay was observed by successful mating indication pheromone response. In conclusion, <i>S. commune</i> can express some <i> S. umbrinum</i> pheromone genes and process some of those gene products that resemble <i>S. commune</i> <i>matB</i> pheromones from their precursor to facilitate a response from <i>S. commune</i> receptors. Factors other than molecular compatibility may keep these signaling molecules in nature from interacting in these two sympatric species. To date, no evidence of self-activation of pheromone signaling within <i>S. umbrinum </i> has been discovered to explain the role of the pheromones in this homothallic species.</p>
| Identifer | oai:union.ndltd.org:PROQUEST/oai:pqdtoai.proquest.com:1590875 |
| Date | 10 July 2015 |
| Creators | Dimick, Emily |
| Publisher | Southern Illinois University at Edwardsville |
| Source Sets | ProQuest.com |
| Language | English |
| Detected Language | English |
| Type | thesis |
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