Poster: Mineral nutrition

Abs # 189: Hydrogen Peroxide Mediates Plant Root Cell Signaling in Response to Nutrient Deprivation

Presenter:	Shin, Ryoung , rshin@danforthcenter.org
Authors	Shin, Ryoung  (A)   McIntyre, Lauren M (B)   Schachtman, Daniel P. (A)
Affiliations:	(A): Donald Danforth Plant Science Center (B): Computational Genomics and Department of Agronomy, Purdue University

Potassium is an essential nutrient required in large quantities, but changes in soil potassium concentrations may limit potassium acquisition by roots. Plants adapt to changes in potassium concentrations to ensure a supply of this nutrient, but it is not known how plant root cells sense or signal the changes that occur upon the onset of potassium deficiency. To understand how roots respond to potassium deficiency at the molecular level, we conducted microarray analyses of gene expression using Arabidopsis roots that had been deprived of K⁺ for two, six, and 30 hours. We found that the genes involved in the production of reactive oxygen species (ROS) were induced when the plants were deprived of potassium. Moreover, we showed that H₂O₂ levels increased after potassium deprivation in planta and that ROS accumulated in a discrete region of roots that has been shown to be active in uptake and translocation of K⁺. Suppression of an NADPH oxidase (rhd2 mutant), which is involved in ROS production, prevented the up-regulation of several genes that are normally induced by potassium 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 the rhd2 mutant and was also sufficient to induce high affinity K⁺ transport activity in roots grown under K⁺ sufficient conditions. Using microarrays we identified loci that were related to ROS production and conducted biochemical and physiological studies to verify that specific cellular responses to potassium deficiency in Arabidopsis roots are activated by ROS.