Date of this Version
PNAS101 (23) June 8, 2004; www.pnas.orgcgidoi10.1073pnas.0401707101
Potassium (K+) is an essential nutrient required by plants in large quantities, but changes in soil concentrations may limit K+ acquisition by roots. It is not known how plant root cells sense or signal the changes that occur after the onset of K+ deficiency. Changes in the kinetics of Rb uptake in Arabidopsis roots occur within 6 h after K+ deprivation. Reactive oxygen species (ROS) and ethylene increased when the plants were deprived of K+. ROS accumulated in a discrete region of roots that has been shown to be active in K+ uptake and translocation. Suppression of an NADPH oxidase in Arabidopsis (rhd2), which is involved in ROS production, prevented the up-regulation of genes that are normally induced by K+ deficiency, but the induction of high-affinity K+ transport activity was unchanged. Application of H2O2 restored the expression of genes induced by K+ deficiency in rhd2 and was also sufficient to induce high-affinity K+ transport activity in roots grown under K+-sufficient conditions. ROS production is an early root response to K+ deficiency that modulates gene expression and physiological changes in the kinetics of K+ uptake.