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JXB Advance Access published online on March 1, 2006
Journal of Experimental Botany, doi:10.1093/jxb/erj115
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© The Author [2006]. Published by Oxford University Press [on behalf of the Society for Experimental Biology]. All rights reserved. For Permissions, please e-mail: journals.permissions@oxfordjournals.org
Received August 9, 2005
Accepted January 11, 2006

SALINITY SPECIAL ISSUE ARTICLE

Cation currents in protoplasts from the roots of a Na+ hyperaccumulating mutant of Capsicum annuum

Meena Murthy 1 and Mark Tester 2 *

1 Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EA, UK; Present address: Department of Medicine, University of Cambridge, UK
2 Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EA, UK; Present address and to whom correspondence should be sent: Australian Centre for Plant Functional Genomics and University of Adelaide, Private Mail Bag 1, Glen Osmond, SA 5064, Australia

* To whom correspondence should be addressed.
Mark Tester, E-mail: mark.tester{at}acpfg.com.au


  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 86Rb+ (K+) and influx of 22Na+ 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 86Rb+ 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.

Keywords: K+ channels; Na+ transport; patch clamp; protoplasts; root cation uptake; salinity tolerance.
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[Abstract] [Full Text] [PDF]


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