Molecular Genetic Analysis of Development and Pathogenicity in the Filamentous Fungus Fusarium verticillioides
Open Access
- Author:
- Guo, Li
- Graduate Program:
- Plant Pathology
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- September 16, 2011
- Committee Members:
- Gretchen Anna Kuldau, Dissertation Advisor/Co-Advisor
Gretchen Anna Kuldau, Committee Chair/Co-Chair
Seogchan Kang, Committee Member
David Michael Geiser, Committee Member
Yinong Yang, Committee Member
Dawn S Luthe, Committee Member
Anthony Glenn, Committee Member - Keywords:
- Fusarium verticillioides
fumonisins
reactive oxygen species
hyphal fusion
genomics
maize
ear rot - Abstract:
- Fusarium verticillioides is a filamentous Ascomycete fungus causing disease on corn seedlings, ear and stalk worldwide. This fungus produces fumonisin mycotoxins posing threats to animal and human health. Disease and mycotoxin management is challenging due to the lack of resistant corn varieties. The mechanisms of how F. verticillioides causes diseases are poorly understood. The purpose of my dissertation research is to identify and functionally analyze F. verticillioides genes that regulate fungal growth, development and pathogenesis. Three candidate genes (FvSO, FvNoxA and FvNoxR) were identified in the F. verticillioides genome and disrupted individually using targeted mutagenesis. Phenotypes of the disruption mutants (ΔFvSO, ΔFvNoxA and ΔFvNoxR) in vegetative growth, sporulation, hyphal branching and anastomosis, fumonisin production and virulence on maize plants were characterized. ΔFvSO had a severely impaired vegetative growth while ΔFvNoxA and ΔFvNoxR growth was not significantly different from wild type. All mutants showed decreased sporulation and ΔFvSO also had delayed conidial germination and aberrant conidial size variation. In addition, ΔFvSO failed to undergo vegetative hyphal fusion. Reactive oxygen species (ROS) levels of ΔFvNoxA and ΔFvNoxR were similar to wild type but ROS hyphal localization in ΔFvNoxR was altered. Hyphal branching of ΔFvNoxA and conidial germ tube branching ΔFvNoxR were abnormal. Moreover, fumonisin B1 production was markedly impaired in all three mutants compared to wild type. Most importantly, all mutants were nonpathogenic on maize seedlings and had attenuated virulence on ears and stalks. These findings will contribute to our understanding of the molecular mechanisms underpinning F. verticillioides growth, development and interaction with the maize host.