Sodium/Potassium Selectivity and Pleiotropy in stl2, a Highly Salt-tolerant Mutation of Ceratopteris richardii

Authors

Thomas R. Warne, University of Tennessee - Knoxville
Leslie G. Hickok, University of Tennessee - Knoxville
Carl E. Sams, University of Tennessee - Knoxville
Dale L. Vogelien, Kennesaw State UniversityFollow

Department

Ecology, Evolution, and Organismal Biology

Document Type

Article

Publication Date

8-1999

Abstract

The roles of Na⁺ and K⁺ (Rb⁺) uptake were further studied in a NaCl-tolerant strain of Ceratopteris richardii containing the stl2 mutation by direct comparison with the wild-type strain. In addition to Na⁺ tolerance, stl2 also confers tolerance to Mg²⁺ and sensitivity to K⁺. In addition to higher K⁺ (Rb⁺) uptake at concentrations commonly associated with low-affinity K⁺ transport, stl2 maintained higher uptake down to 0·1 mol m^–3 Rb⁺. Up to a 25-fold excess of Na⁺ had little effect in either genotype on K⁺ (Rb⁺) uptake at low concentrations, i.e. 0·2 and 0·5 mol m^–3 RbCl. Pretreatment with K⁺ (20 mol m^–3) inhibited uptake of K⁺ (Rb⁺) in the wild type, whereas concurrent inclusion of K⁺ inhibited uptake of Rb⁺ more in stl2. In the absence of K⁺, Na⁺ uptake (0·01–60 mol m^–3) was nearly identical in the wild type and stl2. K⁺ inhibited Na⁺ uptake more effectively in stl2 than the wild type, especially at 60 mol m^–3 Na⁺. Greater inhibition of K⁺ uptake in stl2 occurred with MgCl₂ or TEA (tetraethylammonium chloride) preincubation or with simultaneous inclusion of Al3⁺ (Al₂SO₄). The higher effective velocity of K⁺ uptake at a wide range of concentrations and the enhanced selectivity for K⁺ and against Na⁺ contribute to the preservation of higher cytosolic K⁺ and lower Na⁺ under salinity stress.

Journal Title

Plant, Cell & Environment

Journal ISSN

0140-7791

Volume

22

Issue

8

First Page

1027

Last Page

1034

Digital Object Identifier (DOI)

10.1046/j.1365-3040.1999.00465.x