A rice quantitative trait locus for salt tolerance encodes a sodium transporter

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Many important agronomic traits in crop plants, including stress tolerance, are complex traits controlled by quantitative trait loci (QTLs). Isolation of these QTLs holds great promise to improve world agriculture but is a challenging task. We previously mapped a rice QTL, SKC1, that maintained K+ homeostasis in the salt-tolerant variety under salt stress1, consistent with the earlier finding that K+ homeostasis is important in salt tolerance2,3. To understand the molecular basis of this QTL, we isolated the SKC1 gene by map-based cloning and found that it encoded a member of HKT-type transporters. SKC1 is preferentially expressed in the parenchyma cells surrounding the xylem vessels. Voltage-clamp analysis showed that SKC1 protein functions as a Na+-selective transporter. Physiological analysis suggested that SKC1 is involved in regulating K+/Na+ homeostasis under salt stress, providing a potential tool for improving salt tolerance in crops.

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Figure 1: Identification of the SKC1 QTL and genetic complementation test.
Figure 2: Structural model and expression of SKC1.
Figure 3: SKC1 promoter–GUS expression pattern in transgenic rice plants.
Figure 4: K+ and Na+ contents in rice and functional analysis of SKC1 in oocytes.
Figure 5: Expression and activity of SKC1-GFP fusion proteins in X. laevis oocytes.

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We thank H.-Q. Yang for providing pHB vector, J. Yang, X.-Y. Huang and J.-J. Zhang for technical assistance and E.Y. Isacoff for providing X. laevis oocytes. This work was supported by grants from the Ministry of Science and Technology of China, the National Natural Science Foundation of China and the Shanghai Science and Technology Development Fund to H.-X.L. and a grant from the US Department of Agriculture to S.L.

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Correspondence to Sheng Luan or Hong-Xuan Lin.

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The authors declare no competing financial interests.

Supplementary information

Supplementary Fig. 1

Shoots Na+ contents (means±SE, n=5) in T1 rice transformants under normal or salt stress condition (120 mM NaCl for 7 days). (PDF 32 kb)

Supplementary Fig. 2

Sequence alignments of SKC1. (PDF 56 kb)

Supplementary Fig. 3

K+ and Na+ contents in the phloem sap were not significantly different between NIL(SKC1) and Koshihikari under normal or stress condition (25 mM NaCl). (PDF 34 kb)

Supplementary Fig. 4

NIL(SKC1) seedlings are more tolerant to salt then Koshihikari under salt stress (125 mM NaCl for 32 days). (PDF 158 kb)

Supplementary Table 1

The molecular marker primers developed in this study and primers for SKC1 analysis. (PDF 10 kb)

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