An Arabidopsis thaliana Copper-Sensitive Mutant

To better understand the mechanism of copper metabolism in plants, copper-sensitive (cup) mutants of Arabidopsis thaliana were sought. A population of seeds harvested from self-pollinating plants grown from seeds treated with ethyl methanosulfonate was screened. By testing for the ability to germinate after 48 hours of incubation on media containing 50 μM copper, one mutant, cup2, was found to grow well on normal media, but poorly on 50 μM copper. Grown on the elevated level of copper, the mutant displayed short stature, short roots, and fewer initiated roots. A backcross to the wild-type yielded progeny that tolerated 50 μM copper, indicating the cup2 mutation was recessive to the wild-type allele. Genetic linkage analysis further revealed that the mutated locus was linked to the gl1 locus on chromosome 3. When grown on trace levels of copper (0.5 μM), the mutant accumulated six times more copper than the wild-type. The hyper-accumulation of copper by the mutant suggests the affected gene normally contributes to the regulated movement of copper into or out of the plant.