Hydrogen peroxide mediates plant root cell response to nutrient deprivation

<jats:p> Potassium (K <jats:sup>+</jats:sup> ) is an essential nutrient required by plants in large quantities, but changes in soil concentrations may limit K <jats:sup>+</jats:sup> acquisition by roots. It is not known how plant root cells sense or signal the changes that occur after the onset of K <jats:sup>+</jats:sup> deficiency. Changes in the kinetics of Rb <jats:sup>+</jats:sup> uptake in <jats:italic>Arabidopsis</jats:italic> roots occur within 6 h after K <jats:sup>+</jats:sup> deprivation. Reactive oxygen species (ROS) and ethylene increased when the plants were deprived of K <jats:sup>+</jats:sup> . ROS accumulated in a discrete region of roots that has been shown to be active in K <jats:sup>+</jats:sup> uptake and translocation. Suppression of an NADPH oxidase in <jats:italic>Arabidopsis</jats:italic> ( <jats:italic>rhd2</jats:italic> ), which is involved in ROS production, prevented the up-regulation of genes that are normally induced by K <jats:sup>+</jats:sup> deficiency, but the induction of high-affinity K <jats:sup>+</jats:sup> transport activity was unchanged. Application of H <jats:sub>2</jats:sub> O <jats:sub>2</jats:sub> restored the expression of genes induced by K <jats:sup>+</jats:sup> deficiency in <jats:italic>rhd2</jats:italic> and was also sufficient to induce high-affinity K <jats:sup>+</jats:sup> transport activity in roots grown under K <jats:sup>+</jats:sup> -sufficient conditions. ROS production is an early root response to K <jats:sup>+</jats:sup> deficiency that modulates gene expression and physiological changes in the kinetics of K <jats:sup>+</jats:sup> uptake. </jats:p>