Date of Award

Winter 2006

Project Type

Thesis

Program or Major

Plant Biology

Degree Name

Master of Science

First Advisor

Subhash Minocha

Abstract

Polyamines are low molecular weight nitrogenous compounds found in all living organisms. These omnipresent molecules have been extensively studied in plant systems and have been implicated in a number of physiological responses including growth, development, and stress response. The proposed role of polyamines in vital processes such as cell division and differentiation has sparked enthusiasm in further investigation of this relatively small biosynthetic pathway. Very little is known about the regulation of polyamine biosynthetic genes, an aspect that can elucidate further functions of these ubiquitous compounds. In the following study, the expression profiles of two of these genes, spermidine synthase3 (SPDS3) and spermine synthase (SPMS), were analyzed in the model plant, Arabidopsis thaliana. The promoter::GUS fusion technique was used to provide a detailed expression profile of both genes during the entire life cycle of A. thaliana. Three constructs were designed for each gene containing different segments of the putative promoter region, the entire 5'UTR, and in some cases, a portion of the open reading frame. Each construct was individually transformed into A. thaliana and transformed plants were assayed for GUS activity in every organ, during various time points of development. Overall, the expression of SPDS3 was found to be high in young developing tissues with continued, but weaker, expression in the vascular tissue of mature plants. A similar expression profile was observed for SPMS, however, expression was observed in meristematic and elongating regions of tissue. In addition to the developmental profile, the changes in expression were observed during various abiotic stress conditions. Overall, both SPDS3 and SPMS appear to be induced in response to drought and 100 mM salt stress. There appears to be a slight increase in expression during chilling stress, but expression soon decreased over a 24 h period. SPDS3 was also induced during wounding.

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