Date on Master's Thesis/Doctoral Dissertation

12-2018

Document Type

Doctoral Dissertation

Degree Name

Ph. D.

Department

Biology

Degree Program

Biology, PhD

Committee Chair

Perlin, Michael

Committee Co-Chair (if applicable)

Schultz, David

Committee Member

Schultz, David

Committee Member

Wattenberg, Brian

Committee Member

Klinge, Carolyn

Committee Member

Himes, Paul

Author's Keywords

anther smut; Microbotryum lychnidis-dioicae; effectors; host targets for effectors; biotrophic fungal pathogen; silene latifolia

Abstract

Microbotryum lychnidis-dioicae causes anther smut fungus in its host plant, Silene latifolia. The goal of this work is to identify and characterize the virulence determinants of this pathogen to better understand the molecular basis behind this host-pathogen interaction. This work studied for the first time the key effectors in the mechanism of infection by this fungal species. Using, yeast two-hybrid screens, I have identified the host plant interaction partners for the effector, MVLG_01732. A second effector MVLG_05720, interacts with other fungal proteins that appear to facilitate the fungal establishment and colonization during the infection. Our findings indicate that a third effector, MVLG_04106, could serve as a transcriptional regulator to promote infection. To further characterize the role of the effector, MVLG_01732, I have conducted heterologous expression studies in A. thaliana followed by infection assays with the pathogen Pseudomonas syringae. Our results indicate that this effector has a role in the early bolting of flowers in A. thaliana, this finding provides an important clue about the role of MVLG_01732 in advancing host plant floral development, which is known to occur in infected S. latifolia flowers. Here, we have identified a key molecular link between a fungal effector and the developmental change it triggers in the host plant. Infection assays reveal that this effector might play a role in promoting pathogen growth. I have also examined the response to this effector by the host by expressing the His-tagged effector in S. latifolia in an experiment designed to model the mechanism of infection in the native habitat. This is the first time that this approach of delivering the candidate effector protein has been carried out in planta and aimed to provide information about the previously unidentified interacting partners from the host. Overall, this dissertation body aimed to increase the number of available genetic tools to study M. lychnidis-dioicae and will serve as a valuable resource for future investigators along with furthering our understanding of the infection mechanism.

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