Arabidopsis: A brief introduction

Arabidopsis seedling
My wife, Paulette Werger, is a metalsmith. When asked about the subject of my studies, she responds by saying: "Arabidopsis, a diminutive member of the mustard family, commonly called mouse-eared cress."

My PhD advisor, Michael Sussman doesn't say Arabidopsis, instead he emulates Fred Flintstone in saying: "Araba-dabba-dopsis."

Arabidopsis is a weed. It is also the subject of intense scientific study. These two statements might seem at odds with each other: why expend so much effort on a plant of no commercial value? The reason is simple--Arabidopsis is an excellent model system for plant studies.

Arabidopsis rosette
A model organism
Due to evolution, the basic mechanics of what is learned from one species can often be applied to another species. The study of the bacterium E. coli has revealed much about basic life processes. The study of yeast, a single-celled eukaryote, has revealed information common to all eukaryotic cells. The study of mice, drosophila, and C. elegans have clarified how animals function. And the study of Arabidopsis has been a boon to anyone interested in plants. All these model organisms have certain features that make them easy to manipulate, physically and genetically.

Some of the useful features of Arabidopsis are as follows:
(1) Arabidopsis has a short life cycle, going from seed to seed in about three months.
(2) Each Arabidopsis plant can produce thousands of seeds.
(3) The plants are small and easy to grow. Many genetic screens can be performed on Petri dishes, with a thousand seedlings examined on a single dish.
(4) The genome of Arabidopsis is relatively small, covering about 120 million base pairs (Mb), yet it contains all the information necessary to encode a plant. Compare this to the genome of corn which is more than 10 times as large, at 4,500 Mb.

Not Arabidopsis
The utility of Arabidopsis
For just about any economically important trait in plants, whether it be resistance to pests, the production of vegetable oils, or the quality of wood used in paper products, the genetic basis of these traits is under study in Arabidopsis. Following are two examples of how research on Arabidopsis has been applied to other plants.

(1) Although Arabidopsis is a weed, it is related to a number of vegetables, including broccoli, cabbage, Brussels sprouts, and cauliflower. There is a mutation in Arabidopsis that results in its floral structures taking on a shape similar to a head of cauliflower; not surprisingly, this mutation is called "cauliflower." The laboratory of Martin Yanofsky identified the "cauliflower" gene in Arabidopsis, then examined the homologous gene from the actual cauliflower plant. They found that the cauliflower plant already had a mutation in this gene. Thus from the study of Arabidopsis, we now know why a head of cauliflower looks the way that it does.

(2) The ethylene signaling pathway regulates such processes as fruit ripening, plant senescence, and the abscission of leaves and petals. Genes required for ethylene signaling have been identified in Arabidopsis, including genes that code for ethylene receptors. Mutations in the receptors render the Arabidopsis plant unable to sense ethylene. Armed with this knowledge various laboratories are now isolating similar ethylene receptors from other plant species. The laboratory of Harry Klee, for example, found that a tomato mutation that prevented ripening was in an ethylene receptor. In addition, when the mutant Arabidopsis receptor is expressed in other plant species, these transformed plants now exhibit insensitivity to ethylene. These studies indicate that the mechanism of ethylene perception is conserved in plants, and that we can change the way a plant responds to ethylene by modifying the ethylene receptors.



The general source of Arabidopsis information on the Web is the Arabidopsis database (Atdb).