MAP kinases and transcription factors homologous to Saccharomyces cerevisiae
Fus3p/Kss1p and Ste12p have been identified in several plant pathogenic fungi and
found to be required for pathogenicity and sexual reproduction. A gene encoding the
homolog of Fus3p/Kss1p in Neurospora crassa was isolated previously and named mak-
2 (mitogen activated kinase -2). This dissertation describes the isolation of the Ste12p
homolog, pp-1 (protoperithecia-1) and the comparison of the phenotypes of the mak-2
and pp-1 mutants. The similar phenotypes of the mak-2 and pp-1 null mutants suggest
that these proteins are part of the same MAP kinase signaling cascade in N. crassa. In
addition to reduced growth rate, the phenotypes of the mutants demonstrate that this
pathway is required for female fertility, contributes to aerial hyphal development and
repression of conidiophore development. The mak-2 MAP kinase pathway also regulates
several genes putatively involved in secondary metabolism during the mating process.
Among these is a gene cluster that is likely to be involved in the production of a
polyketide secondary metabolite. An orthologous gene cluster was also identified in M.
grisea, and the structural and functional homology of these two related gene clusters was
characterized. Microarray analysis was used to extend the analysis of gene expression in
mak-2 and pp-1 mutants, and a number of downstream target genes of the MAP kinase
pathway were identified and called mak-2 kinase-regulated genes (mkr). A model of this
MAP kinase pathway in N. crassa was developed. Since N. crassa is a saprophytic
fungus but closely related to several plant pathogens, this research may provide an
important perspective on the evolution of a major regulatory pathway governing fungal
pathogenesis.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/3936 |
| Date | 16 August 2006 |
| Creators | Li, Dan |
| Contributors | Ebbole, Daniel J. |
| Publisher | Texas A&M University |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation, text |
| Format | 17443027 bytes, electronic, application/pdf, born digital |
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