Thellungiella halophila, a salt‐tolerant relative of Arabidopsis thaliana, possesses effective mechanisms to discriminate between potassium and sodium

Abstract

Thellungiella halophila is a salt-tolerant close relative of Arabidopsis thaliana . Significant mRNA similarity was confirmed by hybridization of T. halophila mRNA with the A. thaliana GeneChip ATH1. To establish a platform for future molecular comparison of the two species several physiological mechanisms, which may confer high salt tolerance to T. halophila , were investigated. Determination of ion content in shoots and roots of A. thaliana and T. halophila indicated different strategies of ion uptake and translocation from root to shoot in the two species. During salt stress T. halophila accumulated less sodium than A. thaliana . Tissue concentrations of sodium and potassium showed negative correlation in A. thaliana but not in T. halophila . Electrophysiological experiments proved high potassium/sodium selectivity of root plasma membrane channels in T. halophila. In particular, voltage-independent currents were more selective for potassium in T. halophila than in A. thaliana . Single cell sampling of T. halophila leaves during salt exposure revealed increased concentrations of sodium and decreased concentrations of potassium in epidermal cells suggesting that this cell type could function to ensure storage of sodium and exchange of potassium with the rest of leaf. Application of salt resulted in a sharp drop of transpiration in A. thaliana . By contrast, transpiration in T. halophila responded more slowly and was only slightly inhibited by salt treatment, thus maintaining high water uptake and ion transport.

Nitric Oxide Synthase-Dependent Nitric Oxide Production Is Associated with Salt Tolerance in Arabidopsis

“…To evaluate the effect of salinity on K 1 , Na 1 , and Na 1 to K 1 ratios in shoots of Arabidopsis plants, changes in the element ratios in wild-type Arabidopsis plants were determined after treatment with NaCl. About 4-week-old wild-type plants grown in potting soil were transferred to the basic nutrient solution for 24 h, as described by Volkov et al (2003), and thereafter the plants were treated with 50 and 100 mM NaCl for 48 h. As shown in Figure 1, exposure of Arabidopsis plants to NaCl led to a marked increase in the Na 1 percentage and a decrease in the K 1 percentage, thus resulting in an increase in the Na 1 to K 1 ratio in shoots. The changes in the percentages of K 1 and Na 1 and the Na 1 to K 1 ratio became more evident with increasing concentrations of NaCl from 50 to 100 mM ( Fig.…”

Genome Structures and Halophyte-Specific Gene Expression of the Extremophile Thellungiella parvula in Comparison with Thellungiella salsuginea (Thellungiella halophila) and Arabidopsis

“…salsuginea (salt cress) has been studied as a model halophyte, juxtaposing its physiology and genetic structure to that of Arabidopsis. Suggested mechanisms for tolerance to stress and nutrient-limiting conditions include control over stomatal conductance (Inan et al, 2004), greater discriminatory power of K + -and Na + -transport systems (Volkov et al, 2004;Volkov and Amtmann, 2006), and nitrogen utilization efficiency (Kant et al, 2008). However, a genetic basis of the differences in tolerance could only be deduced by attempts at establishing Arabidopsis-like resources and databases (Inan et al, 2004;Taji et al, 2004Taji et al, , 2008Wang et al, 2004Wang et al, , 2006Gong et al, 2005;Wong et al, 2005;Zhang et al, 2008;Oh et al, 2009).…”

Salt Stress in Thellungiella halophila Activates Na+ Transport Mechanisms Required for Salinity Tolerance

“…These include a small genome of approximately twice the size of Arabidopsis, a short life cycle, self-pollination, and abundant seed production following vernalization, thus allowing for fast and efficient genetic analysis (Bressan et al, 2001). More importantly, the plant has proven easy to transform using the floral-dip method (Bressan et al, 2001) and shares on average 92% sequence identity with Arabidopsis (Bressan et al, 2001;Volkov et al, 2003;Inan et al, 2004). In addition, work is in progress to generate t-DNA-tagged mutant lines Inan et al, 2004).…”