Characterization of the secondary metabolome of a lichenizing fungus
| dc.contributor.author | Bertrand, Robert | |
| dc.contributor.examiningcommittee | McKenna, Sean (Chemistry) O'Neil, Joe (Chemistry) Cardona, Silvia (Microbiology) Zechel, David (Chemistry, Queen's University) | en_US |
| dc.contributor.supervisor | Sorensen, John (Chemistry) | en_US |
| dc.date.accessioned | 2019-06-04T16:29:57Z | |
| dc.date.available | 2019-06-04T16:29:57Z | |
| dc.date.issued | 2019-05 | en_US |
| dc.date.submitted | 2019-05-15T01:21:48Z | en |
| dc.degree.discipline | Chemistry | en_US |
| dc.degree.level | Doctor of Philosophy (Ph.D.) | en_US |
| dc.description.abstract | Lichens are traditionally described as symbionts of fungi and algae and are renowned for their diverse secondary metabolites. How lichens produce these natural products, such as their biosynthetic pathways and the genes that are required to produce these molecules, remains unknown. The genome of the fungal partner of the lichen Cladonia uncialis was de novo sequenced and its genetic secondary metabolome was annotated. This work revealed 48 secondary metabolite biosynthetic gene clusters, providing a first glimpse into the genetic programming of lichen polyketides, terpenes, and non-ribosomal peptides. A ‘deductive approach’ employing retro-biosynthetic reasoning was applied to find the genes responsible for the biosynthesis of usnic acid, the most extensively studied lichen secondary metabolite. A ‘homology mapping’ approach, combining phylogenetics and rational pathway deductions, provided putative assignments of biosynthetic function to nine gene clusters in C. uncialis, including what appears to be gene clusters encoding patulin, the betaenones, 6-hydroxymellein, and grayanic acid. The development of a reliable heterologous expression protocol is a prerequisite to an advanced understanding of lichen secondary metabolite biosynthesis. The heterologous expression of seven C. uncialis polyketide synthases was investigated using the NSAR1 A. oryzae platform. These experiments revealed that A. oryzae can transcribe lichen genes and remove introns to produce translation-coherent mRNA. Though de novo biosynthesis of lichen metabolites was not observed in A. oryzae, this work propels lichen natural product studies into the genomic era and provide a foundation upon which future studies may strive to uncover the rich biosynthetic potential of these enigmatic organisms. | en_US |
| dc.description.note | October 2019 | en_US |
| dc.identifier.uri | http://hdl.handle.net/1993/33943 | |
| dc.language.iso | eng | en_US |
| dc.rights | open access | en_US |
| dc.subject | Secondary Metabolites, Heterologous expression, Cladonia uncialis, Polyketide synthase, Codon bias, Post-translational modifications, Transcription, Genome sequencing, Genome annotation, Homology mapping, Usnic acid, Phylogenetics, Protein modelling, Metabolic pathways | en_US |
| dc.title | Characterization of the secondary metabolome of a lichenizing fungus | en_US |
| dc.type | doctoral thesis | en_US |