Date of Defense

Spring 4-5-2004

Department

Biological Sciences

First Advisor

Alexander Enyedi, Biological Sciences

Second Advisor

Todd Barkman, Biological Sciences

Third Advisor

Hector Quemada, Biological Sciences

Abstract

Salicylic acid (SA) has been shown to be an important signal in activating systemic acquired resistance (SAR) in plants. Endogenous levels of SA are known to increase in response to active oxygen species (AOS) generated during plant-pathogen interactions. A SA derivative, methyl salicylate (MeSA), has been hypothesized to be an alternative mechanism in activating SAR. The salicylic acid carboxyl methyl transferase (SAMT) enzyme catalyzes MeSA formation. Tobacco plants (Nicotiana tabacum L. cv Xanthi-nc, NN genotype) were treated with the AOS generator rose bengal (RB) to determine the effect of free radicals and SA accumulation on the expression of the SAMT gene. Plants transformed with the bacterial nahG gene (unable to accumulate SA) were utilized to observe the effects of free radicals on SAMT expression under reduced levels of SA. Total SA levels in RBtreated NN tobacco leaves increased within twenty-four hours of treatment and remained elevated at forty-eight hours. SAMT gene expression in RB-treated NN tobacco leaves also increased within twenty-four hours and remained elevated at forty-eight hours. The transgenic nahG tobacco leaves did not show an increase in total or free SA in response to RB application. SAMT gene expression in RB-treated transgenic nahG tobacco leaves increased within twenty-four hours and remained elevated at forty-eight hours.

Access Setting

Honors Thesis-Campus Only

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