title: The Arabidopsis thaliana SOS2 gene encodes a protein kinase that is required for salt tolerance.
abstract: In Arabidopsis thaliana, the Salt Overly Sensitive 2 (SOS2) gene is required for intracellular Na(+) and K(+) homeostasis. Mutations in SOS2 cause Na(+) and K(+) imbalance and render plants more sensitive toward growth inhibition by high Na(+) and low K(+) environments. We isolated the SOS2 gene through positional cloning. SOS2 is predicted to encode a serine/threonine type protein kinase with an N-terminal catalytic domain similar to that of the yeast SNF1 kinase. Sequence analyses of sos2 mutant alleles reveal that both the N-terminal catalytic domain and the C-terminal regulatory domain of SOS2 are functionally essential. The steady-state level of SOS2 transcript is up-regulated by salt stress in the root. Autophosphorylation assays show that SOS2 is an active protein kinase. In the recessive sos2-5 allele, a conserved glycine residue in the kinase catalytic domain is changed to glutamate. This mutation abolishes SOS2 autophosphorylation, indicating that SOS2 protein kinase activity is required for salt tolerance.
authors.affiliation: Department of Plant Sciences, University of Arizona, Tucson, AZ 85721, USA.
authors.forename: J
authors.initials: J
authors.lastname: Liu
authors.forename: M
authors.initials: M
authors.lastname: Ishitani
authors.forename: U
authors.initials: U
authors.lastname: Halfter
authors.forename: C S
authors.initials: CS
authors.lastname: Kim
authors.forename: J K
authors.initials: JK
authors.lastname: Zhu
mesh_terms: D000222:Adaptation, Physiological / Q000235:genetics*; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics* / Q000502:physiology; D029681:Arabidopsis Proteins; D001483:Base Sequence; D003001:Cloning, Molecular; D018744:DNA, Plant; D008969:Molecular Sequence Data; D009994:Osmolar Concentration; D018517:Plant Roots / Q000201:enzymology; D017346:Protein Serine-Threonine Kinases / Q000235:genetics*; D012492:Salts; D017386:Sequence Homology, Amino Acid; D015854:Up-Regulation
chemical_list: D029681:Arabidopsis Proteins; D018744:DNA, Plant; D012492:Salts; C406738:SOS2 protein, Arabidopsis; D017346:Protein Serine-Threonine Kinases