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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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(A) Expression analysis of PutHKT2;1 by means of real-time RT-PCR in roots and shoots of P. tenuiflora subjected to 300 mM NaCl (+Na), K+-starvation (–K), and both 300 mM NaCl and K+-starvation stresses (+Na, –K) for 24 h. (B) Time-course expression analysis of PutHKT2;1 in roots of P. tenuiflora. Results are expressed as means ±SE (n=3).
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fig4: (A) Expression analysis of PutHKT2;1 by means of real-time RT-PCR in roots and shoots of P. tenuiflora subjected to 300 mM NaCl (+Na), K+-starvation (–K), and both 300 mM NaCl and K+-starvation stresses (+Na, –K) for 24 h. (B) Time-course expression analysis of PutHKT2;1 in roots of P. tenuiflora. Results are expressed as means ±SE (n=3).

Mentions: Since most HKTs were found to be regulated by K+-starvation and NaCl stress conditions (Kader et al., 2006; Takahashi et al., 2007; Shao et al., 2008), real-time RT-PCR was used to investigate the expression levels of PutHKT2;1 in shoots and roots of P. tenuiflora subjected to NaCl and K+-starvation stresses for 24 h (Fig. 4A). The expression of PutHKT2;1 was induced dramatically in roots under K+-starvation conditions (approximately 25-fold compared with the control). PutHKT2;1 expression in roots was also induced by 300 mM NaCl (1.7-fold compared with the control) or by 300 mM NaCl and K+-starvation stress (3.4-fold compared with the control), but its expression was only slightly regulated by those stresses in shoots. To gain further insight into ionic stress regulation of PutHKT2;1 expression in roots, PutHKT2;1 expression was monitored over a 24 h period (Fig. 4B). Under potassium starvation stress, PutHKT2;1 expression gradually increased. Under 300 mM NaCl, in the presence of both high and low external K+ concentration, PutHKT2;1 transcript levels decreased by approximately 30% compared to the control at 6 h. After 12 h and 24 h of 300 mM NaCl stress, the PutHKT2;1 transcript level at low external K+ concentration was twice that at high external K+ concentration.


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)

(A) Expression analysis of PutHKT2;1 by means of real-time RT-PCR in roots and shoots of P. tenuiflora subjected to 300 mM NaCl (+Na), K+-starvation (–K), and both 300 mM NaCl and K+-starvation stresses (+Na, –K) for 24 h. (B) Time-course expression analysis of PutHKT2;1 in roots of P. tenuiflora. Results are expressed as means ±SE (n=3).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig4: (A) Expression analysis of PutHKT2;1 by means of real-time RT-PCR in roots and shoots of P. tenuiflora subjected to 300 mM NaCl (+Na), K+-starvation (–K), and both 300 mM NaCl and K+-starvation stresses (+Na, –K) for 24 h. (B) Time-course expression analysis of PutHKT2;1 in roots of P. tenuiflora. Results are expressed as means ±SE (n=3).
Mentions: Since most HKTs were found to be regulated by K+-starvation and NaCl stress conditions (Kader et al., 2006; Takahashi et al., 2007; Shao et al., 2008), real-time RT-PCR was used to investigate the expression levels of PutHKT2;1 in shoots and roots of P. tenuiflora subjected to NaCl and K+-starvation stresses for 24 h (Fig. 4A). The expression of PutHKT2;1 was induced dramatically in roots under K+-starvation conditions (approximately 25-fold compared with the control). PutHKT2;1 expression in roots was also induced by 300 mM NaCl (1.7-fold compared with the control) or by 300 mM NaCl and K+-starvation stress (3.4-fold compared with the control), but its expression was only slightly regulated by those stresses in shoots. To gain further insight into ionic stress regulation of PutHKT2;1 expression in roots, PutHKT2;1 expression was monitored over a 24 h period (Fig. 4B). Under potassium starvation stress, PutHKT2;1 expression gradually increased. Under 300 mM NaCl, in the presence of both high and low external K+ concentration, PutHKT2;1 transcript levels decreased by approximately 30% compared to the control at 6 h. After 12 h and 24 h of 300 mM NaCl stress, the PutHKT2;1 transcript level at low external K+ concentration was twice that at high external K+ concentration.

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