Arabidopsis, a small flowering plant that is a relative of the mustard plant, is the basic model organism used in plant biology research. Specifically, we were looking for mutants in the light-responsive pathway. Normally, light represses stem growth so that the stem becomes thicker and can support more leaves. In plants that don t respond well to light due to mutations, the hypocotyl elongates. According to Chory, one mutant produced during their experiments showed signs of overgrowth that is characteristic of auxin overproduction.
Apical dominance is the inhibition of lateral branching characteristically produced by auxin.
These characteristics resulted in a plant that resembled the yucca, so we named the mutant yucca. If the outward appearance of the yucca mutant proved to be caused by auxin overproduction, then the dominant, fertile yucca could offer the first experimental system in which to study how auxin is synthesized. Analysis of the yucca-mutant plants revealed that they did, indeed, show increased auxin levels, said Chory. Also, physiological and genetic experiments on the plants showed that these high auxin levels caused the distinctive growth characteristics of the yucca mutant. Also, the scientists were able to repress yucca s distinctive growth characteristics by using genetic techniques that specifically reduced auxin levels in the mutant plant.