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Cloning of a high-affinity K+ transporter gene PutHKT2;1 from Puccinellia tenuiflora and its functional comparison with OsHKT2;1 from rice in yeast and Arabidopsis.

Ardie SW, Xie L, Takahashi R, Liu S, Takano T - J. Exp. Bot. (2009)

Bottom Line: Arabidopsis over-expressing PutHKT2;1 showed increased sensitivities to Na+, K+, and Li+, while Arabidopsis over-expressing OsHKT2;1 from rice (Oryza sativa) showed increased sensitivity only to Na+.In contrast to OsHKT2;1, which functions in Na+-uptake at low external K+ concentrations, PutHKT2;1 functions in Na+-uptake at higher external K+ concentrations.These results show that the modes of action of PutHKT2;1 in transgenic yeast and Arabidopsis differ from the mode of action of the closely related OsHKT2;1 transporter.

View Article: PubMed Central - PubMed

Affiliation: Asian Natural Environmental Science Center (ANESC), The University of Tokyo, 1-1-1 Midori-cho, Nishitokyo-shi, Tokyo 188-0002, Japan.

ABSTRACT
A high-affinity K+ transporter PutHKT2;1 cDNA was isolated from the salt-tolerant plant Puccinellia tenuiflora. Expression of PutHKT2;1 was induced by both 300 mM NaCl and K+-starvation stress in roots, but only slightly regulated by those stresses in shoots. PutHKT2;1 transcript levels in 300 mM NaCl were doubled by the depletion of potassium. Yeast transformed with PutHKT2;1, like those transformed with PhaHKT2;1 from salt-tolerant reed plants (Phragmites australis), (i) were able to take up K+ in low K+ concentration medium or in the presence of NaCl, and (ii) were permeable to Na+. This suggests that PutHKT2;1 has a high affinity K+-Na+ symport function in yeast. Arabidopsis over-expressing PutHKT2;1 showed increased sensitivities to Na+, K+, and Li+, while Arabidopsis over-expressing OsHKT2;1 from rice (Oryza sativa) showed increased sensitivity only to Na+. In contrast to OsHKT2;1, which functions in Na+-uptake at low external K+ concentrations, PutHKT2;1 functions in Na+-uptake at higher external K+ concentrations. These results show that the modes of action of PutHKT2;1 in transgenic yeast and Arabidopsis differ from the mode of action of the closely related OsHKT2;1 transporter.

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Ion specific sensitivity of PutHKT2;1 and OsHKT2;1 over-expression lines. (A) Seven-day-old WT and transgenic seedlings grown on MS were transferred to minimal-medium (Maser et al., 2002a) supplemented with 75 mM NaCl, 75 mM KCl, and 10 mM LiCl. Seedlings were grown vertically for nine additional days before being photographed. (B) Shoot phenotype of seedling grown in (A). Bar in each picture indicates 1 cm.
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fig7: Ion specific sensitivity of PutHKT2;1 and OsHKT2;1 over-expression lines. (A) Seven-day-old WT and transgenic seedlings grown on MS were transferred to minimal-medium (Maser et al., 2002a) supplemented with 75 mM NaCl, 75 mM KCl, and 10 mM LiCl. Seedlings were grown vertically for nine additional days before being photographed. (B) Shoot phenotype of seedling grown in (A). Bar in each picture indicates 1 cm.

Mentions: PutHKT2;1- and OsHKT2;1-expressing seedlings exhibited normal growth and were indistinguishable from WT plants on minimal medium with respect to root length (Figs 7A, 8) and shoot phenotype (Fig. 7B). Because the functional characterization of PutHKT2;1 and OsHKT2;1 in yeast showed that they have different ion uptake modes, various ionic stresses were imposed (75 mM KCl, 75 mM NaCl, and 10 mM LiCl) in order to determine the ion specificity of the two transporters. Our results showed that OsHKT2;1 over-expression leads to Na-specific sensitivity, as OsHKT2;1-expressing seedlings had shorter roots (Figs 7A, 8A) and chlorotic leaves (Fig. 7B) in the presence of elevated Na+ but not in the presence of K+ and Li+ (Figs 7, 8B, C). Interestingly, PutHKT2;1-expressing seedlings show defective root growth (Figs 7A, 8) and inhibited shoot growth (Fig. 7B) in the presence of all the cations tested, indicating that PutHKT2;1 mediates sensitivity not only to Na+ but also to K+ and Li+, cations that are physically similar to Na+. These results showed that PutHKT2;1 and OsHKT2;1 have different ion specificity.


Cloning of a high-affinity K+ transporter gene PutHKT2;1 from Puccinellia tenuiflora and its functional comparison with OsHKT2;1 from rice in yeast and Arabidopsis.

Ardie SW, Xie L, Takahashi R, Liu S, Takano T - J. Exp. Bot. (2009)

Ion specific sensitivity of PutHKT2;1 and OsHKT2;1 over-expression lines. (A) Seven-day-old WT and transgenic seedlings grown on MS were transferred to minimal-medium (Maser et al., 2002a) supplemented with 75 mM NaCl, 75 mM KCl, and 10 mM LiCl. Seedlings were grown vertically for nine additional days before being photographed. (B) Shoot phenotype of seedling grown in (A). Bar in each picture indicates 1 cm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2724696&req=5

fig7: Ion specific sensitivity of PutHKT2;1 and OsHKT2;1 over-expression lines. (A) Seven-day-old WT and transgenic seedlings grown on MS were transferred to minimal-medium (Maser et al., 2002a) supplemented with 75 mM NaCl, 75 mM KCl, and 10 mM LiCl. Seedlings were grown vertically for nine additional days before being photographed. (B) Shoot phenotype of seedling grown in (A). Bar in each picture indicates 1 cm.
Mentions: PutHKT2;1- and OsHKT2;1-expressing seedlings exhibited normal growth and were indistinguishable from WT plants on minimal medium with respect to root length (Figs 7A, 8) and shoot phenotype (Fig. 7B). Because the functional characterization of PutHKT2;1 and OsHKT2;1 in yeast showed that they have different ion uptake modes, various ionic stresses were imposed (75 mM KCl, 75 mM NaCl, and 10 mM LiCl) in order to determine the ion specificity of the two transporters. Our results showed that OsHKT2;1 over-expression leads to Na-specific sensitivity, as OsHKT2;1-expressing seedlings had shorter roots (Figs 7A, 8A) and chlorotic leaves (Fig. 7B) in the presence of elevated Na+ but not in the presence of K+ and Li+ (Figs 7, 8B, C). Interestingly, PutHKT2;1-expressing seedlings show defective root growth (Figs 7A, 8) and inhibited shoot growth (Fig. 7B) in the presence of all the cations tested, indicating that PutHKT2;1 mediates sensitivity not only to Na+ but also to K+ and Li+, cations that are physically similar to Na+. These results showed that PutHKT2;1 and OsHKT2;1 have different ion specificity.

Bottom Line: Arabidopsis over-expressing PutHKT2;1 showed increased sensitivities to Na+, K+, and Li+, while Arabidopsis over-expressing OsHKT2;1 from rice (Oryza sativa) showed increased sensitivity only to Na+.In contrast to OsHKT2;1, which functions in Na+-uptake at low external K+ concentrations, PutHKT2;1 functions in Na+-uptake at higher external K+ concentrations.These results show that the modes of action of PutHKT2;1 in transgenic yeast and Arabidopsis differ from the mode of action of the closely related OsHKT2;1 transporter.

View Article: PubMed Central - PubMed

Affiliation: Asian Natural Environmental Science Center (ANESC), The University of Tokyo, 1-1-1 Midori-cho, Nishitokyo-shi, Tokyo 188-0002, Japan.

ABSTRACT
A high-affinity K+ transporter PutHKT2;1 cDNA was isolated from the salt-tolerant plant Puccinellia tenuiflora. Expression of PutHKT2;1 was induced by both 300 mM NaCl and K+-starvation stress in roots, but only slightly regulated by those stresses in shoots. PutHKT2;1 transcript levels in 300 mM NaCl were doubled by the depletion of potassium. Yeast transformed with PutHKT2;1, like those transformed with PhaHKT2;1 from salt-tolerant reed plants (Phragmites australis), (i) were able to take up K+ in low K+ concentration medium or in the presence of NaCl, and (ii) were permeable to Na+. This suggests that PutHKT2;1 has a high affinity K+-Na+ symport function in yeast. Arabidopsis over-expressing PutHKT2;1 showed increased sensitivities to Na+, K+, and Li+, while Arabidopsis over-expressing OsHKT2;1 from rice (Oryza sativa) showed increased sensitivity only to Na+. In contrast to OsHKT2;1, which functions in Na+-uptake at low external K+ concentrations, PutHKT2;1 functions in Na+-uptake at higher external K+ concentrations. These results show that the modes of action of PutHKT2;1 in transgenic yeast and Arabidopsis differ from the mode of action of the closely related OsHKT2;1 transporter.

Show MeSH
Related in: MedlinePlus