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

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.

ABA Regulation of Plant Responses to Drought and Salt Stresses

“…HKT transporter genes have also been identified in crop plants, such as wheat and the wheat-relative Triticum monococcum and have similar functions as those in Arabidopsis (Munns et al 2012). Other types of HKT family members, such as TaHKT2;1 from Triticum aestivum, TsHKT1;2 from Thellungiella salsuginea, and EcHKT1;2 from Eucalyptus camaldulensis, also participate in K + transport to maintain K + /Na + balance under salt stress (Ali et al 2012;Ardie et al 2009;Laurie et al 2002;Liu et al 2001;Schachtman and Schroeder 1994). Shkolnik-Inbar et al reported that ABI4 reduced the expression of AtHKT1 to further affect salt tolerance.…”

Potassium and sodium transport in non-animal cells: the Trk/Ktr/HKT transporter family

“…and K ? (in heterologous systems) and active at the plasma membrane of root peripheral layers [14,136] are strongly upregulated at the transcriptional level in response to K ? starvation.…”

“…uptake in planta, at least in conditions of high external Na ? [136]. In rice, OsHKT2;1 has been demonstrated to be involved in nutritional Na ?…”

“…uptake and high or low-affinity Na ? uptake when expressed in yeast or Xenopus oocytes [17,117,119,122,136]. They are able to function in both the inward and outward directions [40,117,119].…”

Salt Adaptation Mechanisms of Halophytes: Improvement of Salt Tolerance in Crop Plants

“…Some ionresponsive antiporter/channel genes have been reported in monocot halophyte Puccinellia tenuifl ora ; PutPMP3 -1, and PutPMP3 -2 encoding plasma membrane protein 3 family prevent the accumulation of excess Na + and K + ions (Zhang et al 2008a ). Similarly, PutHKT2 -1 encoding a high-affi nity K + transporter facilitates K + uptake to maintain a high ratio of K + /Na + in the cells (Ardie et al 2009 ). K + is an essential element in protein synthesis as it binds tRNA to the ribosomes (Blaha et al 2000 ).…”