The model plant Arabidopsis thaliana

Flowering Arabidopsis thaliana

A little plant of big importance

In research laboratories around the world, Arabidopsis thaliana is an important little plant. Scientists work with this non-edible relative of cabbage and radish because it develops, reproduces, and responds to stress and disease in much the same way as crop plants, but is simpler to study. To put it another way, Arabidopsis is to plant biologists what the white mouse is to medical researchers.

Why do scientists work with Arabidopsis?

Arabidopsis takes up minimal space and grows quickly - a plant can grow from seed to maturity in as little as six weeks - in turn producing thousands of seeds. Cultivation is simple and inexpensive, making genetic experiments involving tens of thousands of plants feasible.

Arabidopsis has a small, diploid genome (about 1x10⁸ nucleotide pairs vs. 2x10¹⁰ in garden pea and 3x109 in humans) with little repeated, non-coding DNA, which makes it a great model for genomic analysis.

Once a gene has been discovered in Arabidopsis, the equivalent gene can be found more easily in other plants. What's more, since all flowering plants are closely related, learning about the jobs genes do in Arabidopsis tells researchers a lot about the roles of similar genes in other plants.

Worldwide distribution of Arabidopsis thaliana

The natural history of Arabidopsis

Johannes Thal (hence, thaliana) first described Arabidopsis in the sixteenth century in Germany's Harz Mountains, although he called it Pilosella siliquosa at the time. The name underwent several changes before Arabidopsis thaliana was settled upon in 1842.

Arabidopsis is found in the wild throughout Europe, the Mediterranean, the East African highlands, and Eastern and Central Asia (where it probably originated). It has also been introduced into America and Australia. It grows in pastures and on walls, along paths and on banks. You may have stepped on it but failed to notice. English speakers know Arabidopsis as common wall, mouse ear, or thale cress. In other lands it's known as: almindelig gåsemad (Denmark), lituruoho (Finland), Arabette des dames (France), Ackerschmalwand (Germany), Ludfü (Hungary), shiro-inu-nazuma (Japan), Zanddraket (Netherlands), Vårskrinneblom (Norway), rzodkiewnik (Poland), rezukhovidka Talja (Russia), mostaza silvestre (Spain), and Backrav (Sweden).

Physical Map of Chromosome I and Charts

The history of experimental work in Arabidopsis

Friedrich Laibach published the first experimental work using Arabidopsis in 1907. His microscopic studies suggested the presence of only five chromosomes – an observation that was later confirmed by other investigators. In the 1940s, Laibac's student Erna Reinholz produced the first collection of X-ray induced Arabidopsis mutants.

A few researchers used Arabidopsis during subsequent decades, but not until the advent of modern molecular biology in the late 1970s did plant biologists learn enough about Arabidopsis to see its worth as a model system.

Koorneef and co-workers published the first detailed genetic map (a map showing distances between mutated genes in terms of recombination frequency) of Arabidopsis in 1983. Such maps allow researchers to see the approximate positions of heritable factors (genes and regulatory elements) on chromosomes.

During the 1980s, Arabidopsis' genome was characterised and its first genes sequenced. The production of tagged mutant collections began and methods were developed making it possible to genetically engineer Arabidopsis using Agrobacterium. The generation of physical maps (maps showing distances between genes in terms of DNA length) based on restriction fragment length polymorphisms (RFLPs) began during this time. Such maps allow genes to be located (and then characterised) even when their identity is unknown.

In 1990, scientists outlined a long-range plan for the Multinational Coordinated Arabidopsis thaliana Genome Research Project. This plan called for genetic and physiological experiments to identify, isolate, sequence, and understand Arabidopsis genes; to establish worldwide electronic communication among laboratories; and to create databases so that new knowledge would be shared.

In the following years, plant transformation methods became more efficient. A large number of Arabidopsis mutant lines, gene libraries, and genomic resources were developed and made available to the scientific community through public stock centres. Researchers began to follow the expression of multiple genes at the same time.

The first comprehensive physical map of the Arabidopsis genome was generated using a set of ordered, overlapping fragments of cloned DNA. Published by Mozo et al in 1999, this map provided an important resource for map-based gene cloning and for genome analysis - especially for organising genomic sequencing projects.

In the mid-1990s, the Arabidopsis Genome Initiative, an international effort to sequence the complete Arabidopsis genome, was formed. The results of this effort, a milestone for plant science, were published on 14 December 2000 in Nature.

Arabidopsis research: present and future

Now that Arabidopsis has been fully sequenced, emphasis on functional and comparative genomics is intensifying. This means that scientists are looking at when and where specific genes are expressed to learn more about how plants grow and develop, how they survive in their ever-changing environments, and how gene networks themselves are controlled.

Pot with 9 Arabidopsis plantlets

By enabling work potentially leading to improved crop plants — plants that are more nutritious, more resistant to pests and disease, less prone to crop failure, or that provide higher yields with less damage to the environment — this little plant is doing big things.