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Date of Award

9-2009

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Biology

Supervisor

Robin K. Cameron

Language

English

Abstract

Systemic Acquired Resistancc (SAR) is an induced resistance mechanism in which certain localized pathogen infections lead to broad resistance against future attacks in distant tissues. Resistance is transmitted from induced tissues by long distance signals that are perceived in systemic tissue eliciting defence to normally virulent pathogens. Previous research in the Cameron laboratory indicates that DIR1 may function as a long distance signal during SAR. Agrobacterium transient transformation was used to study DIR1 movement in the dir1-1 SAR-defective mutant. Lower leaves of dir1-1 were infiltrated with Agrobacterium expressing 35S:DIR1-EYFP, followed by inoculation with SAR-inducing Pseudomonas syringae pv. tomato (Pst avrRpt2). Distant leaves were challenged with virulent Pseudomonas syringae pv. tomato (Pst) and bacterial levels were determined. The SAR defect was rescued in dir1-1 plants expressing 35S:DIR1EYFP only if SAR was induced. Petiole exudates were collected from these induced leaves and DIR1 was present, suggesting that DIR1 is capable of movement during SAR. Additionally, when cucumber exudates induced for SAR were infiltrated into dir1-1 rabidopsis, dir1-1 became SAR-competent. Cucumber exudates contained a DIR1-like protein. Taken together, these data suggest that a DIR1-like protein exists in cucumber and functions like DIR1 in Arabidopsis during SAR.

Age-Related Resistance (ARR) has been observed in numerous plant species, often resulting in increased disease resistance as plants mature. A genetic screen to identity potential ARR mutants has been developed. The screen used a florescence strain of Pst (Pst-GFPuv) to quantify bacterial levels in infected leaves. A number of parameters were investigated to improve the screen.

McMaster University Library

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