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

Meena Murthy, Mark Tester*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


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.

Original languageEnglish (US)
Pages (from-to)1171-1180
Number of pages10
JournalJournal of experimental botany
Issue number5
StatePublished - Mar 2006
Externally publishedYes

Bibliographical note

Funding Information:
We thank Mr Paul Freeman for technical assistance, Professor Moshe Tal for seeds, access to unpublished data and much helpful communication during this work; also Dr Anne-Aliénor Véry for useful discussions during the course of this project. MM was supported with a Cambridge Nehru Scholarship and Cambridge Philosophical Society Studentship, and MT thanks the BBSRC and ARC for financial support.


  • K channels
  • Na transport
  • Patch clamp
  • Protoplasts
  • Root cation uptake
  • Salinity tolerance

ASJC Scopus subject areas

  • Physiology
  • Plant Science


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