Intracellular consequences of SOS1 deficiency during salt stress.
A mutation of AtSOS1 (Salt Overly Sensitive 1), a plasma membrane Na(+)/H(+)-antiporter in Arabidopsis thaliana, leads to a salt-sensitive phenotype accompanied by the death of root cells under salt stress. Intracellular events and changes in gene expression were compared during a non-lethal salt stress between the wild type and a representative SOS1 mutant, atsos1-1, by confocal microscopy using ion-specific fluorophores and by quantitative RT-PCR. In addition to the higher accumulation of sodium ions, atsos1-1 showed inhibition of endocytosis, abnormalities in vacuolar shape and function, and changes in intracellular pH compared to the wild type in root tip cells under stress. Quantitative RT-PCR revealed a dramatically faster and higher induction of root-specific Ca(2+) transporters, including several CAXs and CNGCs, and the drastic down-regulation of genes involved in pH-homeostasis and membrane potential maintenance. Differential regulation of genes for functions in intracellular protein trafficking in atsos1-1 was also observed. The results suggested roles of the SOS1 protein, in addition to its function as a Na(+)/H(+) antiporter, whose disruption affected membrane traffic and vacuolar functions possibly by controlling pH homeostasis in root cells.
Oh
Dong-Ha
DH
Division of Applied Life Science (BK21 program) and Environmental BiotechnologyNational Core Research Center, Graduate School of Gyeongsang NationalUniversity, Jinju 660-701, Korea.
Lee
Sang Yeol
SY
Bressan
Ray A
RA
Yun
Dae-Jin
DJ
Bohnert
Hans J
HJ
D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport; D002462:Cell Membrane / Q000235:genetics / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D018517:Plant Roots / Q000235:genetics / Q000378:metabolism; D012965:Sodium Chloride / Q000378:metabolism*; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics / Q000378:metabolism*
D029681:Arabidopsis Proteins; D017923:Sodium-Hydrogen Exchangers; D012965:Sodium Chloride