Arabidopsis thaliana: another "model organism"

This little plant has become to plant biology what Drosophila melanogaster and Caenorhabditis elegans are to animal biology.

Arabidopsis is an angiosperm, a dicot from the mustard family (Brassicaceae). It is popularly known as thale cress or mouse-ear cress. While it has no commercial value — in fact is considered a weed — it has proved to be an ideal organism for studying plant development.

• It has one of the smallest genomes in the plant kingdom: 115,409,949 base pairs of DNA distributed in 5 chromosomes (2n = 10).
• Very little of this is "junk" DNA so most of the DNA encodes its 25,498 genes.
• Transgenic plants can be made easily using Agrobacterium tumefaciens as the vector to introduce foreign genes.
• The plant is small — a flat rosette of leaves from which grows a flower stalk 6–12 inches high.
• It can be easily grown in the lab in a relatively small space.
• Development is rapid. It only takes 5– 6 weeks from seed germination to the production of a new crop of seeds.
• It is a prolific producer of seeds (up to 10,000 per plant) making genetics studies easier.
• Mutations can be easily generated (e.g., by irradiating the seeds or treating them with mutagenic chemicals).
• It is normally self-pollinated so recessive mutations quickly become homozygous and thus expressed.

  Other members of its family cannot self-pollinate. They have an active system of self-incompatibility. Arabidopsis, however, has inactivating mutations in the genes — SRK and SCR — that prevent self-pollination in other members of the family. [Link to discussion.]

• However, Arabidopsis can easily be cross-pollinated to
  • do genetic mapping and
  • produce strains with multiple mutations.

Many of the findings about how plants work — described throughout these pages — were learned from studies with Arabidopsis. (Photo courtesy of Nicole Hanley Markelz of the Plant Genome Research Outreach Program at Cornell University.)