Featured Creature: Mouse-ear cress

What plant was the first to flower in space and is the most widely used model species for studying plant biology?

Arabidopsis thaliana (Mouse-ear cress)!

If you’re a regular reader of Bio4Climate’s Featured Creature series, you might be wondering why I wrote the scientific name of this organism first, rather than its common name. Arabidopsis thaliana (also known as mouse-ear cress, thale cress, or rock cress) is, in fact, recognized by its scientific name more often because it’s one of the most popular organisms used in plant studies and has become the model system of choice for researchers exploring plant biology and comparative genomics. In fact, it’s often dubbed the “white mouse” of the plant research community, making its common name something of a double entendre.

A. thaliana is a small plant with a basal rosette of leaves (a circular or spiral pattern near the base of a plant) that grows up to 9.5 inches (25 cm) in height, and small white flowers that give the plant its name. Mouse-ear is a member of the Brassicaceae (Brass-si-case-see), or mustard, family, which includes plants like —you guessed it— mustard, along with cabbage, broccoli, brussels sprouts, and radish. While A. thaliana is indeed edible like these more economically important crop plants, its capacity as a spring vegetable is not the reason for its fame. More on that story in a minute.

Native to Eurasia and Africa and naturalized worldwide due to human disturbance, A. thaliana is often found by roadsides and other disrupted (or man-made) environments. You have most likely walked by this cruciferous plant without even realizing it. To many, it’s just another weed (though it’s not actually a weed). A. thaliana is widely distributed in habitats with bare, nutrient-poor soil and rocky areas where other plants struggle to establish, needing only air, water, sunlight, and a few minerals to complete its short six-week life cycle. As a self-pollinating plant (selfer), it can also produce seeds without external pollinators. These characteristics help A. thaliana colonize those barren or disturbed areas, making it a pioneer plant—those hardy plants that pave the way and help initiate the development of a plant community.

What makes Arabidopsis thaliana so important in plant research?

Arabidopsis thaliana’s popularity as a leading research organism really exploded when its genome was fully sequenced in 2000. With relatively fewer base pairs of DNA and around 25,000 genes (other plants can have upwards of 30,000-45,000), the plant’s genetic simplicity —paired with its short life cycle— allows researchers to conduct experiments and analyze how specific genes influence development, physiology, and reproduction. Due to the volume of work being focused on the plant since its genome sequencing, A. thaliana is genetically well-characterized, and it’s become an important model system for identifying genes and their functions.

An invaluable effort supporting this research is The Arabidopsis Information Resource (TAIR). The online database offers open access to gene sequences, molecular data, and research findings, fostering collaboration and accelerating discovery. The Nottingham Arabidopsis Stock Centre (NASC) complements TAIR by maintaining the world’s largest seed collection for A. thaliana. With more that one million seed stocks and distribution networks spanning 30 countries, NASC ensures that scientists have ready access to the genetic material they need to push plant science forward.

The plant’s limited space requirements and ability to produce high quantities of seeds and specimens assists in repeated and efficient genetic experiments.

Adept at Adapting

When you think of plants and flowers, words like “fragile” or “delicate” often come to mind. While this may be true, nature is much stronger and more resilient than people first assume. A. thaliana is a prime example of how a small, seemingly weak-looking plant can, in fact, adapt well and keep itself alive. As a plant living in the natural world, A. thaliana has a range of defense mechanisms available to protect against herbivorous insects. Many unique samples of A. thaliana have leaves covered in trichomes, which are bristle-like outgrowths on the outer layer of the plant, that ward off moths and flea beetles. When A. thaliana’s plant tissue is damaged, special compounds call glucosinolates interact with an enzyme, producing toxins that deter most would-be attackers. Studying these Arabidopsis-insect interactions can provide crucial information on mechanisms behind traits that may be important for other plant species.

Using A. thaliana as a research tool has applications for larger, more complex crops. It has furthered our understanding of germination, aspects of plant growth, and been a key to identifying a wide range of plant-specific gene functions.

While A. thaliana has helped form the foundation of modern plant biology, its research informs areas outside strictly plant science as well, including air and soil quality from a public health perspective. A. thaliana can be used as an environmental monitor by tracking its exposure and reaction to different pollutants. This small plant also plays a part in biofuel production and space biology.

Did you say space biology?

Yes, I did! Arabidopsis thaliana was the first plant to flower in space in 1982 aboard the Soviet Salyut 7. Due to its research value, to this day is it one of the most commonly grown plants in space. While it’s not a viable source of food, discoveries made using A. thaliana provide insights that can be applied to a variety of other plants. In the inhospitable environment of space, researchers deploy advanced plant habitats (APHs) with automated water recovery, distribution, atmosphere content, moisture levels, and temperature to assess how A. thaliana’s gene expression and plant health changes in space. When the plants are mature, the crew will freeze or chemically fix samples to preserve them on their journey back down to Earth for further study. Experiments to understand how space affects A. thaliana’s growth and development are key to learning how to keep plants flourishing in space and, some day, help promote long-duration missions for astronauts.

Nature’s little secrets

Nature can be found in the most improbable of places. Yesterday, A. thaliana was just a weed, one of the countless others blooming in places we’ve made natural life nearly impossible. Along a busy road or in the cracks of an aging sidewalk. I’ve stepped over it and driven by it every day without thinking twice.

Today, it’s a rugged little plant growing in some of the most unlikely or inhospitable places, not the least of which is about 250 nautical miles above our heads. A. thaliana’s relatively simple and unremarkable nature is precisely what makes it valuable to science, acting as a sort of legend to help researchers study other plants. It makes me wonder what other of nature’s secrets I pass every day, hidden in plain sight.

Remembering to appreciate those little plants growing on the sidewalk,

Abigail

Sources and Further Reading:

• Arabidopsis thaliana — mouse-ear thale-cress
• Arabidopsis thaliana: a model plant for genome analysis
•  Advantages of using Arabidopsis Thaliana as a Model Organism
• The Arabidopsis Information Resource
• Small model organisms
• Arabidopsis: The Model Plant
• Analysis of Arabidopsis thaliana Growth Behavior in Different Light Qualities, Bettina Bölter et al. 2018
• Biology in Bloom: A Primer on the Arabidopsis thaliana Model System, Andrew Woodward et al., 2018
• Growing Plants in Space
• The Natural History of Model Organisms: Planting molecular functions in an ecological context with Arabidopsis thaliana, Ute Krämer, 2015
• Biochemical Pathways and Environmental Responses in Plants: Part B, Anthony J. Zmuda et al., 2023
• Analysis of the genome sequence of the flowering plant Arabidopsis thaliana, 2023