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Plant Physiol, July 2001, Vol. 126, pp. 1061-1071
The Wheat cDNA LCT1 Generates Hypersensitivity to
Sodium in a Salt-Sensitive Yeast Strain1
Anna
Amtmann,*
Marc
Fischer,
Ellen L.
Marsh,
Aleksandra
Stefanovic,
Dale
Sanders, and
Daniel P.
Schachtman
Department of Biology, P.O. Box 373, York YO10 5YW, United Kingdom
(A.A., M.F., A.S., D.S.); Department of Botany, University of Adelaide,
Adelaide, South Australia 5005, Australia (E.L.M.); and CSIRO Plant
Industry Horticulture Unit, P.O. Box 350, Glen Osmond, South Australia
5064, Australia (D.P.S.)
Salinity affects large areas of agricultural land, and all major
crop species are intolerant to high levels of sodium ions. The
principal route for Na+ uptake into plant cells remains to
be identified. Non-selective ion channels and high-affinity potassium
transporters have emerged as potential pathways for Na+
entry. A third candidate for Na+ transport into plant cells
is a low-affinity cation transporter represented by the wheat protein
LCT1, which is known to be permeable for a wide range of cations when
expressed in yeast (Saccharomyces cerevisiae). To
investigate the role of LCT1 in salt tolerance we have used the yeast
strain G19, which is disrupted in the genes encoding Na+
export pumps and as a result displays salt sensitivity comparable with
wheat. After transformation with LCT1, G19 cells became
hypersensitive to NaCl. We show that LCT1 expression
results in a strong decrease of intracellular
K+/Na+ ratio in G19 cells due to the combined
effect of enhanced Na+ accumulation and loss of
intracellular K+. Na+ uptake through LCT1 was
inhibited by K+ and Ca2+ at high concentrations
and the addition of these ions rescued growth of
LCT1-transformed G19 on saline medium. LCT1 was also shown to mediate the uptake of Li+ and Cs+.
Expression of two mutant LCT1 cDNAs with N-terminal
truncations resulted in decreased Ca2+ uptake and increased
Na+ tolerance compared with expression of the full-length
LCT1. Our findings strongly suggest that
LCT1 represents a molecular link between
Ca2+ and Na+ uptake into plant cells.
1
The work was supported by grants from the
European Union, Biotechnology and Biological Science Research Council,
and the Australian Research Council.
*
Corresponding author; e-mail aa15{at}york.ac.uk; fax
44-1904-434317.
© 2001 American Society of Plant Physiologists
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