Graduation Date

12-2013

Document Type

Master's Thesis

Degree Name

Master of Science

Department or Program

Biological Sciences

Department or Program Chair

Sibdas Ghosh, Ph.D.

First Reader

Sibdas Ghosh, Ph.D.

Second Reader

LaKisha Barrett, Ph.D.

Abstract

The Target of Rapamycin (TOR) kinase is evolutionarily conserved and is a key regulator, controlling many cellular functions to promote survival and growth in all eukaryotes. Several model organisms have indicated a relationship between TOR signaling and life expectancy, such as yeast, fruit flies and mice. Abundant nutrient availability promotes rapid growth and development, whereas depletion of nutrients reduces the activity of the pathways that are involved in growth and nutrient processing. This reduction in activity increases life expectancy, which is supported by evolutionary theories. The confirmed presence of the TOR homolog (a major regulator of growth and cell proliferation) in Arabidopsis thaliana makes this plant an ideal candidate to study for the effects of reduced nutrients in the lifespan extension of plants. To study the role of TOR pathway in lifespan extension in Arabidopsis thaliana, mutant plants with reduced and overexpressed TOR activity were grown in hydroponic culture systems, to monitor the effects of varying nutrient conditions and several senescence associated phenotypes (SAP). During this study we found plants with reduced TOR activity displayed delayed flowering, shattering of siliques, and yellowing of leaves as compared to the wild type plants, whereas plants overexpressing TOR activity displayed early SAP. Further preliminary molecular and physiological analysis shed light on the link between the TOR signaling pathway and

nutrient restriction on Arabidopsis lifespan. We hypothesize that modulating TOR may slow the aging process in Arabidopsis, through downstream processes including mRNA translation, protein synthesis, autophagy, and stress responses. However challenges presented by plants to the general theories of biological aging as it differs in plants in several fundamental ways from the processes in animals. Therefore identifying the mechanisms through which Arabidopsis TOR (AtTOR) functions in plants may aid in developing stress resistant strains that could provide tools for improving crop yield and creating long lasting plants such as fruits and vegetables, as well as benefit the floral industry by providing fresh and long lasting flowers.

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