Abstract
In Arabidopsis, primary root elongation is known to be inhibited by excess iron, while promoted by iron deficiency. Since iron is generally one of the limiting factors for plant growth, it is important for plants to control root development in response to iron status. However, molecular mechanism underlying the control of root development in relation to iron is still unclear. Here we report the (i) establishment of a novel bioassay system that detects responses of root elongation in response to iron status, and the (ii) isolation of mutants that exhibit defects in such responses. We first found that primary root elongation speed of Arabidopsis seedlings was approximately 10 mm/day on 1/2 MS medium when iron and phosphorous are omitted. However, the root elongation speed was decreased when excess iron was supplied during the assay. Using this bioassay system, we obtained at least 4 mutant lines with altered responses to exogenous iron supply through the screening of 8,000 M2 seeds of fast neutrons mutants (65 Gy), and confirmed that the traits are inheritable in their progeny. These mutants might be useful genetic tools to understand the iron sensing mechanism of plants.
