Date on Senior Honors Thesis
5-2019
Document Type
Senior Honors Thesis
Degree Name
B.S.
Department
Biology
Degree Program
College of Arts and Sciences
Author's Keywords
genetics; fungus; infection; pathogen
Abstract
Ustilago maydis is a model organism for study of fungal mating and host infection. Two compatible haploid mating types must mate to form a dikaryon in order for the fungus to infect its host, corn (Zea mays). There are a variety of genetic mechanisms that regulate mating and infection in the fungus, many of which coregulate both processes. The aim of this study was to investigate how alteration of certain regulatory proteins in U. maydis affects these basic processes as well as how alteration of genes involved in signaling pathways can affect the expression of one another. Primarily, the focus was on exploring the role of the ptn1 gene. This gene was disrupted and therefore found to be involved in tumorigenesis and teliospore development during infection. Additional disruption of the ust1 and unh1 genes, which play opposite roles in tumorigenesis, was attempted on these ptn1 deletion strains of U. maydis using a high fidelity CRISPR-Cas9 system to examine the influence of these genes on the ptn1 pathway. Further experiments were intended to generate ptn1 deletion mutant strains of U. maydis in which the pdc1 gene, encoding a major protein involved in cellular regulation, was simultaneously overexpressed. Phenotypes of pdc1 overexpression mutants of U. maydis were examined for both effects on U. maydis cells in culture and during plant infection. Ptn1 deletion strains were found to be more susceptible to cell wall stress, displayed lesser aerial hyphae formation during mating, and showed reduced infection symptoms including reduced tumor size and reduced number of tumors. Overexpression of pdc1 led to no changes in mating or virulence in wild type strains but may exert an added effect on ptn1 deletion strains and their corresponding phenotypes.
Recommended Citation
Desmarais, John S., "Genetic crosstalk and its effects on virulence and mating in Ustilago maydis." (2019). College of Arts & Sciences Senior Honors Theses. Paper 200.
Retrieved from https://ir.library.louisville.edu/honors/200
Lay Summary
Ustilago maydis is a fungus that infects corn (Zea mays), causing the formation of tumors filled with fungal spores on the corn plant. To infect, two compatible mating types of the fungus must mate to activate genes responsible for infection. There are a variety of genes that influence fungal mating and infection that work in concert. The aim of this study was to investigate how alteration of certain genes in U. maydis affects the mating and infection processes as well as how the altered genes interact with one another Primarily, the focus was on exploring the role of the ptn1 gene. This gene is involved in tumor formation and spore development during infection. Additional disruption of the ust1 and unh1 genes, which play opposite roles in tumor formation, was attempted on ptn1 deletion strains of U. maydis using CRISPR-Cas9 gene editing. Further experiments were intended to generate ptn1 deletion mutant strains of U. maydis in which the pdc1 gene, which is involved cellular regulation, was simultaneously overexpressed. pdc1 mutants of U. maydis were examined for both effects on mating and plant infection. Ptn1 deletion strains were found to be more susceptible to cell wall stress, displayed lesser mating response, and showed reduced infection symptoms including reduced tumor size and reduced number of tumors. Overexpression of pdc1 led to no changes in mating or virulence in wild type strains but may exert an added effect on ptn1 deletion strains.
