Title page for ETD etd-06292005-140540


Type of Document Master's Thesis
Author Mohr, Toni Jolene
URN etd-06292005-140540
Title Dissecting Transcriptional Regulation of Rpp8 in Arabidopsis thaliana
Degree Master of Science
Department Plant Pathology, Physiology, and Weed Science
Advisory Committee
Advisor Name Title
McDowell, John M. Committee Chair
Jelesko, John G. Committee Member
Nessler, Craig L. Committee Member
Keywords
  • Arabidopsis thaliana
  • RPP8
  • Hyaloperonospora parasitica
  • R gene
  • disease
Date of Defense 2005-06-15
Availability unrestricted
Abstract
Plants have evolved physical barriers and inducible defense responses to combat

microbial pathogens. Inducible responses are mediated by R proteins, which recognize

invading pathogens. R proteins must be precisely regulated to provide effective

resistance, without inhibiting normal plant growth. However, little is known about R

gene regulation under defense-inducing conditions. The interaction between the

oomycete Hyaloperonospora parasitica and the model plant Arabidopsis thaliana

provides an excellent model system to explore R gene regulation. My research focuses

on RPP8, a CC-NBS-LRR gene, which provides resistance to the H. parasitica isolate

Emco5. Previous work in the McDowell lab suggested that RPP8 is upregulated during

defense responses. My research shows that RPP8 alleles from the Columbia and

Landsberg erecta ecotypes are upregulated by H. parasitica and the defense signaling

molecule salicylic acid, suggesting a potential feedback loop. RPP8-Ler is also

systemically upregulated after infection of the bacterial pathogen Pseudomonas syringae

pv. tomato DC3000. Additionally, RPP8-Ler expression is increased during wounding

and heat stress. I also examined the role of regulatory cis elements in the RPP8

promoter. Three W-boxes are essential for basal and inducible RPP8 expression, and are

required for resistance to Emco5. The X-box, a unique cis element in the RPP8

promoter, is essential for strong basal expression and wound-induced upregulation, and

affects spatial expression of RPP8-Ler. However, the X-box is not required for RPP8-Ler upregulation during pathogen or SA treatment. R genes may be induced as part of

global defense responses, which could prime the host for more effective pathogen

recognition.

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