Date of Graduation

2006

Document Type

Thesis

Degree Type

MS

Committee Chair

Daniel G. Panaccione

Abstract

Ergot alkaloids, a category of mycotoxins produced by various fungi, adversely affect both humans and animals. Several plant-associated fungi in the genera Claviceps, Neotyphodium, and Epichloe (order Hypocreales) produce an array of ergot alkaloids. Another fungus, Aspergillus fumigatus that occupies a completely different ecological niche and is classified under the order Eurotiales, also produces ergot alkaloids. The gene clusters predicted to encode the enzymes required for ergot alkaloid production within these species are strikingly similar, however, they are poorly understood. In this study, a gene knockout of the easC gene that encodes a putative catalase resulted in the loss of ergot alkaloid production in A. fumigatus. Complementation of the knockout mutant with a wild-type easC allele restored ergot alkaloids, showing that easC controls an essential step within the pathway. Incubation of the easC knockout mutant with the pathway intermediate chanoclavine restored ergot alkaloid production demonstrating that easC plays an essential role in a step prior to chanoclavine. Additional studies involving lysergyl peptide synthetase 1, an enzyme essential for the assembly of the ergopeptines within Neotyphodium and Claviceps species, demonstrated the existence of an additional copy of the gene in Neotyphodium coenophialum. These studies suggest an evolutionary change allowing production of divergent alkaloids. Dehydroergovaline, a second ergopeptine found in N. coenophialum-infected tall fescue, was shown to not result from plant modification of ergovaline. These data indicate that dehydroergovaline is produced directly by N. coenophialum.

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