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The Putative Plasma Membrane Na⁺/H⁺ Antiporter SOS1 Controls Long-Distance Na⁺ Transport in Plants
Ist Teil von
The Plant cell, 2002-02, Vol.14 (2), p.465-477
Ort / Verlag
United States: American Society of Plant Biologists
Erscheinungsjahr
2002
Link zum Volltext
Quelle
EZB Free E-Journals
Beschreibungen/Notizen
The salt tolerance locus SOS1 from Arabidopsis has been shown to encode a putative plasma membrane Na+/ H+ antiporter. In this study, we examined the tissue-specific pattern of gene expression as well as the Na+ transport activity and subcellular localization of SOS1. When expressed in a yeast mutant deficient in endogenous Na+ transporters, SOS1 was able to reduce Na+ accumulation and improve salt tolerance of the mutant cells. Confocal imaging of a SOS1-green fluorescent protein fusion protein in transgenic Arabidopsis plants indicated that SOS1 is localized in the plasma membrane. Analysis of SOS1 promoter-β-glucuronidase transgenic Arabidopsis plants revealed preferential expression of SOS1 in epidermal cells at the root tip and in parenchyma cells at the xylem/symplast boundary of roots, stems, and leaves. Under mild salt stress (25 mM NaCl), sos1 mutant shoot accumulated less Na+ than did the wild-type shoot. However, under severe salt stress (100 mM NaCl), sos1 mutant plants accumulated more Na+ than did the wild type. There also was greater Na+ content in the xylem sap of sos1 mutant plants exposed to 100 mM NaCl. These results suggest that SOS1 is critical for controlling long-distance Na+ transport from root to shoot. We present a model in which SOS1 functions in retrieving Na+ from the xylem stream under severe salt stress, whereas under mild salt stress it may function in loading Na+ into the xylem.