title: Cation currents in protoplasts from the roots of a Na+ hyperaccumulating mutant of Capsicum annuum.
abstract: A wilty mutant (scabrous diminutive, sd) of Capsicum annuum L. hyperaccumulates Na+ in all tissues and has a lower K+ content in the roots. This has been shown to be due to a greater efflux of (86)Rb+ (K+) and influx of (22)Na+ in the mutant. In this study, the transporters responsible for these fluxes were investigated by applying patch clamp techniques to protoplasts derived from root cortical cells. Inwardly rectifying K+ currents were comparable in the two genotypes, but a characteristically bigger outward K+ current was observed in protoplasts from mutant roots, correlating with a bigger efflux of (86)Rb+ from mutant plants. Whole-cell currents due to the movement of Na+ have also been studied in both genotypes. The magnitude of the time-independent inward currents that conduct Na+ at hyperpolarizing voltages were comparable in both genotypes. However, microelectrode measurements of membrane potentials in cortical cells of roots in high Na+ conditions revealed that the membrane potentials of the root cells in the mutants were approximately 60 mV more negative than in wild-type root cells. Quantitatively, this hyperpolarization is calculated to be sufficient to account for the increased Na+ influx in the mutants.
authors.affiliation: Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EA, UK.
authors.forename: Meena
authors.initials: M
authors.lastname: Murthy
authors.forename: Mark
authors.initials: M
authors.lastname: Tester
mesh_terms: D002212:Capsicum / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism; D002412:Cations / Q000378:metabolism; D005838:Genotype; D007473:Ion Channels / Q000037:antagonists & inhibitors; D017136:Ion Transport / Q000235:genetics / Q000502:physiology; D008564:Membrane Potentials; D009154:Mutation; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D018517:Plant Roots / Q000166:cytology / Q000235:genetics / Q000378:metabolism; D011188:Potassium / Q000378:metabolism; D011523:Protoplasts / Q000378:metabolism* / Q000502:physiology; D012964:Sodium / Q000378:metabolism*; D027981:Symporters / Q000235:genetics / Q000378:metabolism
chemical_list: D027682:Cation Transport Proteins; D002412:Cations; C088864:HKT1 protein, plant; D007473:Ion Channels; D010940:Plant Proteins; D027981:Symporters; D012964:Sodium; D011188:Potassium