Differentiation of low-affinity Na+ uptake pathways and kinetics of the effects of K+ on Na+ uptake in the halophyte Suaeda maritima

Zhang, Jin-Lin, Flowers, Timothy J and Wang, Suo-Min (2013) Differentiation of low-affinity Na+ uptake pathways and kinetics of the effects of K+ on Na+ uptake in the halophyte Suaeda maritima. Plant and Soil, 368 (1-2). pp. 629-640. ISSN 0032-079X

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Abstract

Background and aims Salinity is an increasing problem for agricultural production worldwide. Understanding how Na+ enters plants is important if reducing Na+ influx, a key component of the regulation of Na+ accumulation in plants and improving salt tolerance of crop plants, is to be achieved. Our previous work indicated that two distinct low-affinity Na+ uptake pathways exist in the halophyte Suaeda maritima. Here, we report the external NaCl concentration at which uptake switches from pathway 1 to pathway 2 and the kinetics of the interaction between external K+ concentration and Na+ uptake and accumulation in S. maritima in order to determine the roles of K+ transporters or channels in low-affinity Na+ uptake. Methods Na+ influx, Na+ and K+ accumulations in S. maritima exposed to various concentrations of NaCl (0-200 mM) were analyzed in the absence and presence of the inhibitors TEA and Ba+ (5 mM TEA or 3 mM Ba2+) or KCl (0, 10 or 50 mM). Results Our earlier proposal was confirmed and extended that there are two distinct low-affinity Na+ uptake pathways in S. maritima: pathway 1 might be mediated by a HKT-type transporter under low salinity conditions and pathway 2 by an AKT1-type channel or a KUP/HAK/KT type transporter under high salinity conditions. The external NaCl concentration at which two distinct low-affinity Na+ uptake switches from pathway 1 to pathway 2, the 'turning point', is between 90 and 95 mM. Over a short period (12 h) of Na+ and K+ treatments, a low concentration of K+ (10mM) facilitated Na+ uptake by S. maritima under high salinity (100-200 mM NaCl), whether or not the plants had been subjected to a longer (3 d) period of K+ starvation. The kinetics suggests that low concentration of K+ (10 mM) might activate AKT1-type channels or KUP/HAK/KT-type transporters under high salinity (100-200 mM NaCl). Conclusions The turning-point of external NaCl concentrations for the two low-affinity Na+ uptake pathways in Suaeda maritima is between 90 and 95 mM. A low concentration of K+ (10 mM) might activate AKT1 or KUP/HAK/KT and facilitate Na+ uptake under high salinity (100-200 mM NaCl). The kinetics of K+ on Na+ uptake and accumulation in S maritima are also consistent with there being two low-affinity Na+ uptake pathways.

Item Type: Article
Additional Information: Times Cited: 0 Zhang, Jin-Lin Flowers, Timothy J. Wang, Suo-Min
Keywords: Suaeda maritima Low-affinity Na+ uptake Effects of K+ on Na+ uptake HKT AKT1 KUP/HAK/KT alkali cation transport salt tolerance puccinellia-tenuiflora salinity tolerance sodium-transport barley roots radial transport plasma-membrane arabidopsis plants
Schools and Departments: School of Life Sciences > Evolution, Behaviour and Environment
Subjects: Q Science > QK Botany > QK0710 Plant physiology
Depositing User: Tim Flowers
Date Deposited: 14 Jan 2014 11:09
Last Modified: 14 Jan 2014 11:09
URI: http://sro.sussex.ac.uk/id/eprint/47358
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