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Date of Award

Spring 1996

Document Type

Restricted Thesis: Campus only access

Degree Name

Bachelor of Science

Department

Biology

First Advisor

Dr. Brad Goodner

Abstract

Leaf and stem trichomes (epidermal hairs) in the flowering plant Arabidopsis provide an excellent model for the study of asymmetric cell growth. The goal of this project was to perform a genetic analysis of trichrome mutations in an attempt to isolate genes which play a role in the asymmetric cell growth of the trichromes.

The problem that I addressed in this project deals with the differentiation of cells that undergo asymmetric cell growth. This process occurs in many different organisms such as nematodes, amphibians, mammals, and flowering plants. For example, the first division of the zygote of flowering plants occurs asymmetrically (Goodner, 1993). For this project I chose trichromes on the Arabidopsis as model system for asymmetric growth. Among a host of other possible models in the flowering plant, such as root hairs or pollen tubes, trichomes are a convenient and effective system.

Trichomes are small hair-like protrusions emerging from the epidermis of the stems and leaves of plants (see Figure 1). Because of the small size, short life cycle, and compact genome of Arabidopsis, trichomes on Arabidopsis plants make an excellent laboratory model. For these same reasons, Arabidopsis has enjoyed a recent popularity in labs, which provides us with a wealth of background information and correspondence possibilities.

In studying the polar growth of plant cells, a reasonable place to start is the genetic level. Because the plant's genome is at the core of it development, much information can be learned about what controls the growth and differentiation of particular cells by looking at the genome. Thus, in my study I looked to the genome of Arabidopsis. Each trichome mutation that we found may indicate the presence of a previously unrecognized gene that plays a role in the polar development of the trichome.

What is already known about trichome development includes the results of several other mutations. For example, the ttg mutant is known to lack certain pigments and seed coat mucilage in addition to lacking trichomes (Koornneef, 1981). The glabrous (gl) locus is known to act as a transcription factor. (Oppenheimer, 1991) These two mutants are only a small part of the at least 21 unidentified genes that are expected to affect trichome development (Marks, 1994; Hulskamp, 1994) (see Figure 2). By using the trichomes of Arabidopsis as a model, this information will contribute to the general knowledge of asymmetric growth in organisms.

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