Semester

Fall

Date of Graduation

2020

Document Type

Dissertation

Degree Type

PhD

College

Davis College of Agriculture, Natural Resources and Design

Department

Division of Plant and Soil Sciences

Committee Chair

Daniel Panaccione

Committee Member

Matthew Kasson

Committee Member

F. Heath Damron

Committee Member

Werner Geldenhuys

Abstract

Ergot alkaloids are fungal tryptophan derived toxins which affect mammalian circulation and neurotransmission. These compounds are biosynthesized by a conserved genetic pathway, known as the ergot alkaloid synthesis (EAS) pathway by fungi belonging to the ascomycete families Trichocomaceae and Clavicipitaceae. Several Ipomoea species and related plants in the morning glory family harbor vertically transmitted symbiotic fungi in the genus Periglandula, also members of Clavicipitaceae, that produce ergot alkaloids. Metabolomic analysis of seeds identified a previously uncharacterized glycoside form of the pharmaceutically important ergot alkaloid, ergonovine. Several species belonging to the fungal genus Metarhizium have recently been shown to have the capacity to express lysergic acid derived compounds. Metarhizium species are prolific entomopathogens and have the capacity to form beneficial relationships with plants by colonizing their roots. Proteomics analysis showed that wildtype and knock out strains of Metarhizium brunneum infected insects had different antimicrobial peptide and protein expression profiles based on the presence of ergot alkaloids. Metabolomics analysis found that unlike with insects, M. brunneum does not produce ergot alkaloids when grown in conjunction with plants and factors known to promote microbial symbiosis and stress-response in plants were upregulated. Fungi from Trichocomaceae (genera include Penicillium) diverge from fungi in Clavicipitaceae at a middle step of the ergot alkaloid synthetic (EAS) pathway to produce fumigaclavines and related compounds. Penicillium biforme is a known producer of rugulovasine A/B, which has never been observed in Penicillium camemberti. Data presented here suggest that the ancestor of modern P. camemberti had the capacity to synthesize rugulovasines and other ergot alkaloid precursors but lost this capability due to a V13G mutation on the protein. Analysis of the genomes from P. camemberti and P. biforme revealed that the two species contain the same cluster of EAS genes, and both organisms express mRNA from these genes in specific culture conditions. Metabolomics analysis confirmed that the regulatory elements needed for EAS gene expression are functional in P. camemberti. These results show how genetic techniques and biochemical analysis can provide new insights into these organisms.

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