Screening and characterization of cesium-resistant mutants from mutagenized Arabidopsis thaliana

To isolate mutants of Arabidopsis, which is frequently used for experimental molecular botany, in Cs uptake or accumulation, we have devised a screening method using the x-ray analytical microscope microanalysis of leaves. A double screening method was used to isolate 54 Cs-resistant mutants. The seeds for the selection, M2 seeds, were derived from ethyl methane sulfonate (EMS)-treated plants. In the first screening experiment, EMS-mutagenized seeds were sown in medium containing 3 mM Cs. In this condition, the wild type Arabidopsis usually died in the medium, however Cs-resistant mutants survived. These surviving seedlings were transferred into soil for harvest of first-screening-seeds. In the successive experiment, the first-screening-seeds were sown in MS medium containing 1 mM Cs, and Cs concentration in the leaves was analyzed with an x-ray analytical microscope. We obtained 54 mutants in Cs uptake or accumulation after screening over 100,000 seedlings. These mutants showed either excessive accumulation of Cs in leaves or an inability to accumulate Cs to a normal concentration. The uptake rates of Cs in those mutants were also examined by using 134-Cs radioactive tracer. (author)