title: Cadmium impairs ion homeostasis by altering K+ and Ca2+ channel activities in rice root hair cells.
abstract: Cadmium (Cd2+) interferes with the uptake, transport and utilization of several macro- and micronutrients, which accounts, at least in part, for Cd2+ toxicity in plants. However, the mechanisms underlying Cd2+ interference of ionic homeostasis is not understood. Using biophysical techniques including membrane potential measurements, scanning ion-selective electrode technique for non-invasive ion flux assays and patch clamp, we monitored the effect of Cd2+ on calcium (Ca2+) and potassium (K+) transport in root hair cells of rice. Our results showed that K+ and Ca2+ contents in both roots and shoots were significantly reduced when treated with exogenous Cd2+. Further studies revealed that three cellular processes may be affected by Cd2+, leading to changes in ionic homeostasis. First, Cd2+ -induced depolarization of the membrane potential was observed in root hair cells, attenuating the driving force for cation uptake. Second, the inward conductance of Ca2+ and K+ was partially blocked by Cd2+, decreasing uptake of K+ and Ca2+ . Third, the outward K+ conductance was Cd2+ -inducible, decreasing the net content of K+ in roots. These results provide direct evidence that Cd2+ impairs uptake of Ca2+ and K+, thereby disturbing ion homeostasis in plants.
authors.affiliation: NJU-NJFU Joint Institute for Plant Molecular Biology, School of Life Sciences, Nanjing University, Nanjing 210093, China.
authors.forename: Sun
authors.initials: S
authors.lastname: Li
authors.forename: Jingling
authors.initials: J
authors.lastname: Yu
authors.forename: Minjie
authors.initials: M
authors.lastname: Zhu
authors.forename: Fugeng
authors.initials: F
authors.lastname: Zhao
authors.forename: Sheng
authors.initials: S
authors.lastname: Luan
mesh_terms: D001692:Biological Transport / Q000187:drug effects; D002104:Cadmium / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D006706:Homeostasis / Q000187:drug effects; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D012275:Oryza / Q000187:drug effects* / Q000378:metabolism; D018408:Patch-Clamp Techniques; D018517:Plant Roots / Q000187:drug effects* / Q000378:metabolism; D011188:Potassium / Q000378:metabolism; D015221:Potassium Channels / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology
chemical_list: D015220:Calcium Channels; D015221:Potassium Channels; D002104:Cadmium; D011188:Potassium; D002118:Calcium