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dc.contributor.authorKim, Kwang Hyungen_US
dc.date.accessioned2014-03-14T21:19:13Z
dc.date.available2014-03-14T21:19:13Z
dc.date.issued2009-09-07en_US
dc.identifier.otheretd-09202009-155703en_US
dc.identifier.urihttp://hdl.handle.net/10919/39452
dc.description.abstractAlternaria brassicicola is a necrotrophic pathogen that causes black spot disease on virtually all cultivated Brassicas, A. brassicicola is renowned for its ability to prodigiously produce secondary metabolites. To test the hypothesis that secondary metabolites produced by A. brassicicola contribute to pathogenicity, we identified seven nonribosomal peptide synthetases (NPSs) and 10 polyketide synthases (PKSs) in the A. brassicicola genome. The phenotype resulting from knockout mutations of each PKS and NPS gene was investigated with an emphasis on discovery of fungal virulence factors. A highly efficient gene disruption method using a short linear double stranded DNA construct with minimal elements was developed, optimized, and used to functionally disrupt all NPS and PKS genes in A. brassicicola. Three NPS and two PKS genes, and one NPS-like gene appeared to be virulence factors based upon reduced lesion development of each mutant on inoculated green cabbage and Arabidopsis compared with the wild-type strain. Furthermore some of the KO mutants exhibited developmental phenotypic changes in pigmentation and conidiogenesis. To further characterize the roles of several genes of interest in A. brassicicola development and pathogenesis, the genes AbNPS2, AbPKS9, and NPS-like tmpL were selected for in-depth functional analysis. We provide substantial evidence that the AbNPS2-associated metabolite is involved in conidial cell wall construction, possibly as an anchor connecting two cell wall layers. We also characterized a biosynthetic gene cluster harboring the AbPKS9 gene and demonstrated that this cluster is responsible for the biosynthesis of depudecin, an inhibitor of histone deacetylases and a minor virulence factor. Finally, we demonstrated that a NPS-like protein named TmpL is involved in a filamentous fungi-specific mechanism for regulating levels of intracellular reactive oxygen species during conidiation and pathogenesis in both plant and animal pathogenic fungi. Collectively our results indicate that small molecule nonribosomal peptides and polyketides in A. brassicicola play diverse, but also fundamental, roles in fungal development and pathogenesis.en_US
dc.publisherVirginia Techen_US
dc.relation.haspartKim_KH_D_2009.pdfen_US
dc.rightsI hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to Virginia Tech or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report.en_US
dc.subjectfungal pathogenicityen_US
dc.subjectSecondary metaboliteen_US
dc.subjectAlternaria brassicicolaen_US
dc.subjectNonribosomal peptide synthetaseen_US
dc.subjectPolyketide synthaseen_US
dc.titleFunctional Analysis of Secondary Metabolite Biosynthesis-Related Genes in Alternaria brassicicolaen_US
dc.typeDissertationen_US
dc.contributor.departmentBiologyen_US
dc.description.degreePh. D.en_US
thesis.degree.namePh. D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen_US
thesis.degree.disciplineBiologyen_US
dc.contributor.committeechairLawrence, Christopher B.en_US
dc.contributor.committeememberMcDowell, John B.en_US
dc.contributor.committeememberLi, Liwuen_US
dc.contributor.committeememberTholl, Dorothea B.en_US
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-09202009-155703/en_US
dc.date.sdate2009-09-20en_US
dc.date.rdate2009-10-07
dc.date.adate2009-10-07en_US


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