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Thesis Format

Monograph

Degree

Master of Science

Program

Chemistry

Supervisor

Sumarah, Mark W.

Affiliation

Agriculture and Agri-Food Canada

2nd Supervisor

Yeung, Ken K.-C.

Co-Supervisor

Abstract

Potato wart is an infection of cultivated potato plants caused by the soil-borne biotrophic fungus Synchitrium endobioticum. The main symptoms of infection are formation of warts on the tuber tissue and the production of biflagellated mobile spores that undergo long-lasting dormancy periods. Genomic studies have significantly contributed to an overall understanding of the fungal life cycle, including the discovery of the first S. endobioticum avirulence genes, and the identification of multiple pathotypes. However, the molecular pathways involved in host-pathogen interactions during potato wart infection and the factors contributing to resistance in plants remain unknown. In this work, a combination of proteomic analysis and protein structure analysis resulted in the discovery of protein classes associated with immune response-based changes post-infection. Comparative proteomics of four potato varieties highlighted the differences in resistance between groups. Co-immunoprecipitation experiments led to detection of interaction partners of recombinant AvrSen1 protein, providing insight into its localization and functions.

Summary for Lay Audience

The fungal kingdom is estimated to contain around 11 million different species that vary in structure, functions, and preferred living environments. Many different types of fungi grow on plants and can have either beneficial or harmful effects on the growth and development of certain crops, including potatoes. One of the fungal infections that results in major crop losses in Canada and worldwide is potato wart. The pathogen that causes this infection is not well-understood and the factors that play a role in disease progression remain unknown. Previous research indicated that the fungus responsible for potato wart is capable of producing chemicals that facilitate the infection. Identifying these fungal molecules may aid in understanding the mechanisms the fungus is using to attack potato plants. Mass spectrometry (MS) is an analytical technique that determines the structure and mass of molecules that are present in the sample. The components of the sample mixture are broken down into fragments that are then detected by the instrument. These generated fragments are characteristic of their overall chemical structure, where fragmentation patterns can be compared and matched to libraries of previously identified chemicals to confirm their identity. In this study, mass spectrometry was used to compare the differences in protein levels between uninfected and infected tubers. Overall, around 600 proteins were identified in each variety. Following data analysis, it was determined that different potato varieties respond to infection differently.

In addition to protein analysis, the other goal of this project was to express, purify, and characterize one of the effector proteins that is produced by the fungus. By mixing the purified fungal protein with protein extracts from tuber tissue, we were able to identify protein-protein interactions that occur between the plant and the fungus.

Creative Commons License

Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.

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