Arabidopsis
Arabidopsis thaliana, a small weed in the mustard family, is to plant biology what the fruit fly is to animal biology: the workhorse model. It is unremarkable to look at — a low rosette of leaves and tiny white flowers — but for genetics it is ideal because it is small, grows fast, and a single plant produces thousands of seeds.
Arabidopsis has one of the most compact genomes among flowering plants, and it was the first plant to have its full genome sequenced. Its genes can be readily mutated and altered, large mutant collections exist, and its short generation time lets researchers run experiments across plant generations within a single year, an impossibility with crops like trees.
Although Arabidopsis is not itself a crop, the genes and pathways worked out in it — how roots and flowers form, how plants sense light and respond to drought, how they defend against disease — are largely shared with food plants. So discoveries in this little weed feed directly into understanding and improving agriculture.
By isolating Arabidopsis mutants with flowers built from the wrong parts — petals where stamens should be — researchers deduced the genetic rules that assign each whorl of a flower its identity.
A roadside weed that revealed how flowers are patterned.
Flower development in Arabidopsis is governed by homeotic genes much like those in animals, leading to the classic “ABC model,” in which combinations of a few genes specify whether an organ becomes a petal, stamen or other part.