A Single Amino-Acid Substitution in the Sodium Transporter HKT1 Associated with Plant Salt Tolerance  . Issue 3 (9th May 2016)

• Record Type: Journal Article
• Authors: Ali, Akhtar; Raddatz, Natalia; Aman, Rashid; Kim, Songmi; Park, Hyeong Cheol; Jan, Masood; Baek, Dongwon; Khan, Irfan Ullah; Oh, Dong-Ha; Lee, Sang Yeol; Bressan, Ray A.; Lee, Keun Woo; Maggio, Albino; Pardo, Jose M.; Bohnert, Hans J.; Yun, Dae-Jin
• Is Part Of: Plant physiology. Volume 171:Issue 3(2016)
• Page Start: 2112
• Page End: 2126
• Publication Date: 2016-05-09
• Subjects: Plant physiology -- Periodicals; Botany -- Periodicals; Periodicals; Electronic journals; 571.2
• DOI: 10.1104/pp.16.00569
• Languages: English
• ISSNs: 0032-0889

Abstract

Abstract : HKT1-type transporters with an Asp (D) in the second pore-loop domain display inward-rectification and reduced affinity for Na +, in contrast to those with Asn (N) in this position that transport Na + . Abstract: A crucial prerequisite for plant growth and survival is the maintenance of potassium uptake, especially when high sodium surrounds the root zone. The Arabidopsis HIGH-AFFINITY K + TRANSPORTER1 (HKT1), and its homologs in other salt-sensitive dicots, contributes to salinity tolerance by removing Na + from the transpiration stream. However, TsHKT1;2, one of three HKT1 copies in Thellungiella salsuginea, a halophytic Arabidopsis relative, acts as a K + transporter in the presence of Na + in yeast ( Saccharomyces cerevisiae ). Amino-acid sequence comparisons indicated differences between TsHKT1;2 and most other published HKT1 sequences with respect to an Asp residue (D207) in the second pore-loop domain. Two additional T . salsuginea and most other HKT1 sequences contain Asn (n ) in this position. Wild-type TsHKT1;2 and altered AtHKT1 (AtHKT1 N-D ) complemented K + -uptake deficiency of yeast cells. Mutant hkt1 - 1 plants complemented with both AtHKT1 N - D and TsHKT1;2 showed higher tolerance to salt stress than lines complemented by the wild-type AtHKT1 . Electrophysiological analysis in Xenopus laevis oocytes confirmed the functional properties of these transporters and the differential selectivity for Na + and K + based on the n /d variance in the pore region. This change also dictated inward-rectification for Na + transport. Thus, the introduction of Asp, replacing Asn, in HKT1-type transporters established altered cation selectivity and uptake dynamics. We describe one way, based on a single change in a crucial protein that enabled some crucifer species to acquire improved salt tolerance, which over evolutionary time may have resulted in further changes that ultimately facilitated colonization of saline habitats.