Master of Science
Sumarah, Mark W.
Yeung, Ken K.-C.
Fungi from Canadian crops affect many aspects of agriculture. For example, ginseng root rot caused by Ilyonectria spp. is a major issue for farmers. Ilyonectria spp. make few reported natural products and it is not known if those products are unique to virulent species. PCA and molecular networking were applied to HRMS data to establish a distinct metabolomic profile of root rot pathogens, characterized by antifungal resorcyclic acid lactones (RALs). These likely protect Ilyonectria from other soil pathogens, which gives it the opportunity to infect ginseng root.
Molecular networking was also applied to fungal endophytes from fruit crops to identify new compounds. Endophytes are symbionts that produce beneficial compounds, however, traditional screening methods are cumbersome in finding new or novel compounds. HRMS data of 302 fungal endophytes were examined to identify nine new compounds related to known antimicrobial compounds. These compounds are targets for isolating and characterizing in further studies.
Summary for Lay Audience
There are many kinds of fungi that affect agriculture, ranging from harmful to helpful. Often the effects they have on plants are due to chemicals they produce, which are named natural products. Ginseng root rot is caused by a fungal infection and results in large crop losses for Canadian farmers every year. The pathogen that causes this disease was studied to determine what kinds of natural products it makes, and what role those products may have in the life of the fungus and its host, ginseng. Mass spectrometry is an analytical technique that measures the mass of chemicals and also allows us to break chemicals into fragments. Similarly shaped chemicals produce similar types of fragments and this similarity can be assessed by a technique named molecular networking. Using molecular networking it was determined that fungi that cause ginseng root rot produce a family of structurally related natural products that can kill other types of fungi. These compounds likely help ginseng root rot fungus ward off other fungi living in its environment to give it a better chance of survival, which in turn allows it to infect ginseng root.
Molecular networking was also applied to another group of fungi to identify new compounds. Fungal endophytes grow in mutually beneficial relationships with plants. They grow inside leaves and stems without harming their host, and produce natural products that protect their hosts from other more harmful organisms. In return they receive a safe place to live and nutrients to grow. Many of the chemicals they make are used as medicinal drugs, pesticides, or have value in chemical research. By examining fungi and their natural products we can discover new chemicals that may be of use. However, the processes used to find new compounds from fungi are often lengthy and difficult. Therefore, 302 fungal endophytes found in Canadian fruit crops were analyzed by molecular networking to identify undiscovered natural products. Molecular networking simplified and sped up the process of finding new compounds. Nine new compounds were found that are related to known compounds that have antimicrobial activity. These compounds will be isolated and have their structures characterized in future studies.
DesRochers, Natasha, "Analysis of Secondary Metabolites Biosynthesized by Pathogenic and Symbiotic Fungi using High-Resolution Tandem LC-MS and Spectral Molecular Networking" (2020). Electronic Thesis and Dissertation Repository. 7331.
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