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1.  Functional characterization in Xenopus oocytes of Na+ transport systems from durum wheat reveals diversity among two HKT1;4 transporters 
Journal of Experimental Botany  2013;65(1):213-222.
HKT1;4 was linked to a salt tolerance QTL in wheat. Here, two wheat HKT1;4-type transporters were functionally characterised in Xenopus oocytes. Beside shared properties, differences in Na+ transport affinity were evidenced. Such functional diversity sheds light on the QTL bases
Plant tolerance to salinity constraint involves complex and integrated functions including control of Na+ uptake, translocation, and compartmentalization. Several members of the high-affinity K+ transporter (HKT) family, which comprises plasma-membrane transporters permeable to K+ and Na+ or to Na+ only, have been shown to play major roles in plant Na+ and K+ homeostasis. Among them, HKT1;4 has been identified as corresponding to a quantitative trait locus (QTL) of salt tolerance in wheat but was not functionally characterized. Here, we isolated two HKT1;4-type cDNAs from a salt-tolerant durum wheat (Triticum turgidum L. subsp. durum) cultivar, Om Rabia3, and investigated the functional properties of the encoded transporters using a two-electrode voltage-clamp technique, after expression in Xenopus oocytes. Both transporters displayed high selectivity for Na+, their permeability to other monovalent cations (K+, Li+, Cs+, and Rb+) being ten times lower than that to Na+. Both TdHKT1;4-1 and TdHKT1;4-2 transported Na+ with low affinity, although the half-saturation of the conductance was observed at a Na+ concentration four times lower in TdHKT1;4-1 than in TdHKT1;4-2. External K+ did not inhibit Na+ transport through these transporters. Quinine slightly inhibited TdHKT1;4-2 but not TdHKT1;4-1. Overall, these data identified TdHKT1;4 transporters as new Na+-selective transporters within the HKT family, displaying their own functional features. Furthermore, they showed that important differences in affinity exist among durum wheat HKT1;4 transporters. This suggests that the salt tolerance QTL involving HKT1;4 may be at least in part explained by functional variability among wheat HKT1;4-type transporters.
PMCID: PMC3883290  PMID: 24192995
Durum wheat; electrophysiology; HKT1;4; salt tolerance; sodium transport; Xenopus oocyte.
2.  Plant dehydrins and stress tolerance 
Plant Signaling & Behavior  2011;6(10):1503-1509.
Dehydrins (DHNs), or group 2 LEA (Late Embryogenesis Abundant) proteins, play a fundamental role in plant response and adaptation to abiotic stresses. They accumulate typically in maturing seeds or are induced in vegetative tissues following salinity, dehydration, cold and freezing stress. The generally accepted classification of dehydrins is based on their structural features, such as the presence of conserved sequences, designated as Y, S and K segments. The K segment representing a highly conserved 15 amino acid motif forming amphiphilic a-helix is especially important since it has been found in all dehydrins. Since more than 20 y, they are thought to play an important protective role during cellular dehydration but their precise function remains unclear. This review outlines the current status of the progress made toward the structural, physico-chemical and functional characterization of plant dehydrins and how these features could be exploited in improving stress tolerance in plants.
PMCID: PMC3256378  PMID: 21897131
abiotic stress; dehydration stress; drought; cold acclimation; freezing tolerance; LEA proteins; dehydrins

Results 1-2 (2)