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The High-Affinity Potassium Transporter EpHKT1;2 From the Extremophile Eutrema parvula Mediates Salt Tolerance

To survive salt stress, plants must maintain a balance between sodium and potassium ions. High-affinity potassium transporters (HKTs) play a key role in reducing Na(+) toxicity through K(+) uptake. Eutrema parvula (formerly known as Thellungiella parvula), a halophyte closely related to Arabidopsis,...

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Detalles Bibliográficos
Autores principales: Ali, Akhtar, Khan, Irfan Ullah, Jan, Masood, Khan, Haris Ali, Hussain, Shah, Nisar, Muhammad, Chung, Woo Sik, Yun, Dae-Jin
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Frontiers Media S.A. 2018
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6077265/
https://www.ncbi.nlm.nih.gov/pubmed/30105045
http://dx.doi.org/10.3389/fpls.2018.01108
Descripción
Sumario:To survive salt stress, plants must maintain a balance between sodium and potassium ions. High-affinity potassium transporters (HKTs) play a key role in reducing Na(+) toxicity through K(+) uptake. Eutrema parvula (formerly known as Thellungiella parvula), a halophyte closely related to Arabidopsis, has two HKT1 genes that encode EpHKT1;1 and EpHKT1;2. In response to high salinity, the EpHKT1;2 transcript level increased rapidly; by contrast, the EpHKT1;1 transcript increased more slowly in response to salt treatment. Yeast cells expressing EpHKT1;2 were able to tolerate high concentrations of NaCl, whereas EpHKT1;1-expressing yeast cells remained sensitive to NaCl. Amino acid sequence alignment with other plant HKTs showed that EpHKT1;1 contains an asparagine residue (Asn-213) in the second pore-loop domain, but EpHKT1;2 contains an aspartic acid residue (Asp-205) at the same position. Yeast cells expressing EpHKT1;1, in which Asn-213 was substituted with Asp, were able to tolerate high concentrations of NaCl. In contrast, substitution of Asp-205 by Asn in EpHKT1;2 did not enhance salt tolerance and rather resulted in a similar function to that of AtHKT1 (Na(+) influx but no K(+) influx), indicating that the presence of Asn or Asp determines the mode of cation selectivity of the HKT1-type transporters. Moreover, Arabidopsis plants (Col-gl) overexpressing EpHKT1;2 showed significantly higher tolerance to salt stress and accumulated less Na(+) and more K(+) compared to those overexpressing EpHKT1;1 or AtHKT1. Taken together, these results suggest that EpHKT1;2 mediates tolerance to Na(+) ion toxicity in E. parvula and is a major contributor to its halophytic nature.