title: Comparative effect of potassium on K and Na uptake and transport in two accessions of Arabidopsis thaliana during salinity stress.
abstract: Potassium-sodium interaction was compared in two natural accessions of Arabidopsis thaliana, Columbia-0 and NOK2. Seedlings were grown in the presence of 0 or 50 mM NaCl and 0.1; 0.625 or 2.5 mM K(+). At the lowest K(+) concentration, salt treatment inhibited both K(+) uptake and growth. Increasing the K(+) availability did not modified salt response in Columbia-0, but restored nearly normal net K(+) uptake in NaCl condition and alleviated NaCl growth reduction in NOK2. The effect of K(+) and NaCl on transcript level of several K(+) and Na(+) transporters in both shoots and roots was assessed using semi-quantitative RT-PCR. The mRNA abundance of the NHX1 and SOS1 Na(+)/H(+) antiporters was significantly increased by 50 mM NaCl in the two accessions. NHX1, which is responsible for Na(+) sequestration into vacuoles, was more up-regulated in NOK2 leaves than in Columbia-0's in NaCl stress condition. AKT1, which is the major channel involved in K(+) absorption, was down-regulated in salt stress condition, but was not responding to K(+) treatments. Only in NOK2, SKOR and AKT2, which respectively control xylem and phloem K(+) transport, were markedly up-regulated by 2.5 mM K(+) in both roots and shoots, independently of NaCl. Phenotypic and gene expression analyses suggest that the relative salt tolerance of NOK2 is mainly due to a high ability to sequester Na(+) in the vacuole and to take up and transport K(+). Up-regulation of SKOR and AKT2 by K(+), and of NHX1 by NaCl could participate in determining this phenotype.
authors.affiliation: Physiologie et biochimie de la tolérance au sel des plantes, faculté des sciences de Tunis, campus universitaire, 1060 Tunis, Tunisia. rym_kaddour@yahoo.fr
authors.forename: Rym
authors.initials: R
authors.lastname: Kaddour
authors.forename: Nawel
authors.initials: N
authors.lastname: Nasri
authors.forename: Sabah
authors.initials: S
authors.lastname: M'rah
authors.forename: Pierre
authors.initials: P
authors.lastname: Berthomieu
authors.forename: Mokhtar
authors.initials: M
authors.lastname: Lachaâl
mesh_terms: D017360:Arabidopsis / Q000187:drug effects / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001693:Biological Transport, Active; D003470:Culture Media; D010641:Phenotype; D018515:Plant Leaves / Q000382:microbiology; D018517:Plant Roots / Q000382:microbiology; D011188:Potassium / Q000378:metabolism* / Q000494:pharmacology*; D012313:RNA / Q000096:biosynthesis / Q000302:isolation & purification; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012964:Sodium / Q000378:metabolism*; D012965:Sodium Chloride / Q000494:pharmacology*
chemical_list: D029681:Arabidopsis Proteins; D003470:Culture Media; D012965:Sodium Chloride; D012313:RNA; D012964:Sodium; D011188:Potassium