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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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Related in: MedlinePlus

Comparison of Na+ and K+ accumulation in shoots and roots between WT, PutHKT2;1, and OsHKT2;1 over-expression lines. Seven-day-old WT and transgenic seedlings grown on MS were transferred to minimal-medium supplemented with the indicated salts. Seedlings were grown vertically for 14 additional days before being harvested. For each treatment, the ion content was determined from a pool of 15 plants. Results are expressed as means ±SE (n=3). Asterisks indicate a significant difference from the WT (P <0.05) by Student's t test.
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fig11: Comparison of Na+ and K+ accumulation in shoots and roots between WT, PutHKT2;1, and OsHKT2;1 over-expression lines. Seven-day-old WT and transgenic seedlings grown on MS were transferred to minimal-medium supplemented with the indicated salts. Seedlings were grown vertically for 14 additional days before being harvested. For each treatment, the ion content was determined from a pool of 15 plants. Results are expressed as means ±SE (n=3). Asterisks indicate a significant difference from the WT (P <0.05) by Student's t test.

Mentions: The Na+ and K+ contents of WT, PutHKT2;1, and OsHKT2;1 transgenic seedlings were determined. Figure 11 shows that the Na+ and K+ accumulation patterns of WT and transgenic seedlings were similar between shoot and root. PutHKT2;1 and OsHKT2;1 transgenic seedlings accumulated more Na+ than the WT when the growth medium contained 50 mM Na+ and 1.75 mM K+ (Fig. 11A, upper panel). Interestingly, external Na+ addition significantly reduced the K+ content of OsHKT2;1-expressing seedlings but had little effect on the K+ content of PutHKT2;1-expressing seedlings (Fig. 11A, lower panel). Furthermore, the Na+ and K+ contents of PutHKT2;1-expressing seedlings did not significantly differ from those of the WT when grown in the presence of 50 mM Na+ and 0.1 mM K+, confirming that PutHKT2;1 does not mediate Na+ uptake under low external K+ concentration. The Na+ accumulation in shoots and roots of PutHKT2;1-expressing seedlings was decreased when the [CaExt2+] was increased from 3 mM to 10 mM, but higher [CaExt2+] did not greatly affect the Na+ accumulation of OsHKT2;1-expressing seedlings. Overall, the Na-sensitivity symptoms of PutHKT2;1- and OsHKT2;1-expressing seedlings were due, primarily, to decreased K+ to Na+ ratios both in the shoot and root (Fig. 11B).


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)

Comparison of Na+ and K+ accumulation in shoots and roots between WT, PutHKT2;1, and OsHKT2;1 over-expression lines. Seven-day-old WT and transgenic seedlings grown on MS were transferred to minimal-medium supplemented with the indicated salts. Seedlings were grown vertically for 14 additional days before being harvested. For each treatment, the ion content was determined from a pool of 15 plants. Results are expressed as means ±SE (n=3). Asterisks indicate a significant difference from the WT (P <0.05) by Student's t test.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig11: Comparison of Na+ and K+ accumulation in shoots and roots between WT, PutHKT2;1, and OsHKT2;1 over-expression lines. Seven-day-old WT and transgenic seedlings grown on MS were transferred to minimal-medium supplemented with the indicated salts. Seedlings were grown vertically for 14 additional days before being harvested. For each treatment, the ion content was determined from a pool of 15 plants. Results are expressed as means ±SE (n=3). Asterisks indicate a significant difference from the WT (P <0.05) by Student's t test.
Mentions: The Na+ and K+ contents of WT, PutHKT2;1, and OsHKT2;1 transgenic seedlings were determined. Figure 11 shows that the Na+ and K+ accumulation patterns of WT and transgenic seedlings were similar between shoot and root. PutHKT2;1 and OsHKT2;1 transgenic seedlings accumulated more Na+ than the WT when the growth medium contained 50 mM Na+ and 1.75 mM K+ (Fig. 11A, upper panel). Interestingly, external Na+ addition significantly reduced the K+ content of OsHKT2;1-expressing seedlings but had little effect on the K+ content of PutHKT2;1-expressing seedlings (Fig. 11A, lower panel). Furthermore, the Na+ and K+ contents of PutHKT2;1-expressing seedlings did not significantly differ from those of the WT when grown in the presence of 50 mM Na+ and 0.1 mM K+, confirming that PutHKT2;1 does not mediate Na+ uptake under low external K+ concentration. The Na+ accumulation in shoots and roots of PutHKT2;1-expressing seedlings was decreased when the [CaExt2+] was increased from 3 mM to 10 mM, but higher [CaExt2+] did not greatly affect the Na+ accumulation of OsHKT2;1-expressing seedlings. Overall, the Na-sensitivity symptoms of PutHKT2;1- and OsHKT2;1-expressing seedlings were due, primarily, to decreased K+ to Na+ ratios both in the shoot and root (Fig. 11B).

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