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The AtNHX1 exchanger mediates potassium compartmentation in vacuoles of transgenic tomato
Author(s) -
Leidi Eduardo O.,
Barragán Verónica,
Rubio Lourdes,
ElHamdaoui Abdelaziz,
Ruiz M. Teresa,
Cubero Beatriz,
Fernández José A.,
Bressan Ray A.,
Hasegawa Paul M.,
Quintero Francisco J.,
Pardo José M.
Publication year - 2010
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/j.1365-313x.2009.04073.x
Subject(s) - vacuole , cytosol , xylem , antiporter , sodium–hydrogen antiporter , limiting , microbiology and biotechnology , cytoplasm , biochemistry , biology , intracellular , transgene , potassium , gene isoform , chemistry , sodium , botany , enzyme , gene , membrane , mechanical engineering , organic chemistry , engineering
Summary NHX‐type antiporters in the tonoplast have been reported to increase the salt tolerance of various plants species, and are thought to mediate the compartmentation of Na + in vacuoles. However, all isoforms characterized so far catalyze both Na + /H + and K + /H + exchange. Here, we show that AtNHX1 has a critical involvement in the subcellular partitioning of K + , which in turn affects plant K + nutrition and Na + tolerance. Transgenic tomato plants overexpressing AtNHX1 had larger K + vacuolar pools in all growth conditions tested, but no consistent enhancement of Na + accumulation was observed under salt stress. Plants overexpressing AtNHX1 have a greater capacity to retain intracellular K + and to withstand salt‐shock. Under K + ‐limiting conditions, greater K + compartmentation in the vacuole occurred at the expense of the cytosolic K + pool, which was lower in transgenic plants. This caused the early activation of the high‐affinity K + uptake system, enhanced K + uptake by roots, and increased the K + content in plant tissues and the xylem sap of transformed plants. Our results strongly suggest that NHX proteins are likely candidates for the H + ‐linked K + transport that is thought to facilitate active K + uptake at the tonoplast, and the partitioning of K + between vacuole and cytosol.