Identification of genes regulating the plant-specific expression of the ItmM gene in Epichloe festucae : this thesis is presented as a partial fulfillment of the requirements for the degree of Master of Science (Msc) in Genetics at Massey University, Palmerston North, New Zealand

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dc.contributor.authorBrasell, Emma
dc.date.accessioned2009-11-30T22:35:53Z
dc.date.availableNO_RESTRICTIONen_US
dc.date.available2009-11-30T22:35:53Z
dc.date.issued2008
dc.description.abstractThe fungal endophyte Epichloë festucae forms a largely mutualistic association with the ryegrass species Lolium perenne. E. festucae produces a range of bio-protective alkaloids that protect the host grass from herbivory by both mammals and insects. One such alkaloid, Lolitrem B, is a potent mycotoxin and the causative agent of ryegrass staggers in livestock. Ten genes required for biosynthesis of lolitrem B are encoded in the ltm gene cluster. The ltm genes are expressed in a plant-specific manner, with high levels of expression in planta and very low levels of expression in culture. The mechanism regulating ltm gene expression is unknown but it is predicted to involve signalling from the host plant. The ltmM gene was chosen for use in the investigation of ltm gene regulation because the flanking regions do not contain retrotransposon sequence, which surrounds much of the ltm gene cluster. To identify fungal genes involved in the plant-induced expression of ltmM, a mutagenesis and screening system was developed using a PltmM-gusA ‘knock-in’ construct to detect expression from the ltmM promoter. Agrobacterium tumefaciens-mediated T-DNA mutagenesis was used to create a set of mutants with random insertions in the genome. Mutants were then screened for altered PltmM-gusA expression, both in culture and in planta. Three mutants were identified with increased PltmM-gusA expression in culture, however, no mutants were identified with loss of PltmM-gusA expression in planta. This indicates that a mechanism of repression is involved in the plant-induced expression of ltmM, either directly or indirectly. TM mutants of interest were also observed for altered symbiosis phenotypes. Mutants were identified with reduced colonisation rates and altered hyphal growth in planta. Integration sites were identified for two colonisation mutants and the disrupted genes are predicted to be the CTP:cholinephosphate cytidylyltransferase (CCT) gene PCT1 and the mitogen-activated protein kinsase kinase (MAPKK) gene mkk2.en_US
dc.identifier.urihttp://hdl.handle.net/10179/1106
dc.language.isoenen_US
dc.publisherMassey Universityen_US
dc.rightsThe Authoren_US
dc.subjectEndophytic fungien_US
dc.subjectLolium perenneen_US
dc.subjectPerennial ryegrassen_US
dc.subjectGene expressionen_US
dc.subject.otherFields of Research::270000 Biological Sciences::270200 Genetics::270201 Gene expressionen_US
dc.titleIdentification of genes regulating the plant-specific expression of the ItmM gene in Epichloe festucae : this thesis is presented as a partial fulfillment of the requirements for the degree of Master of Science (Msc) in Genetics at Massey University, Palmerston North, New Zealanden_US
dc.typeThesisen_US
massey.contributor.authorBrasell, Emma
thesis.degree.disciplineGeneticsen_US
thesis.degree.grantorMassey Universityen_US
thesis.degree.levelMastersen_US
thesis.degree.nameMaster of Science (M. Sc.)en_US
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