title: Regulation of aquaporin-mediated water transport in Arabidopsis roots exposed to NaCl.
abstract: The effects of Ca(NO3)2, KF and okadaic acid (OA) on cell hydraulic responses to NaCl were examined in roots of Arabidopsis thaliana wild-type plants and compared with plants overexpressing plasma membrane intrinsic protein PIP2;5. Root treatment with 10 mM NaCl rapidly and sharply reduced cell hydraulic conductivity (L(p)) in the wild-type Arabidopsis plants, but had no effect on L(p) in Arabidopsis plants overexpressing PIP2;5, suggesting that changes in protein and aquaporin gene expression were among the initial targets responsible for the inhibition of L(p) by NaCl. The down-regulation of PIP transcripts after 1 h exposure to 10 mM NaCl was likely a significant factor in the reduction of L(p). The effect of NaCl on L(p) in the wild-type plants was abolished when the NaCl-treated roots were subsequently exposed to 5 mM KF, 5 mM Ca(NO3)2 and 5 µM OA. The reduction of L(p) by 5 mM KF could not be prevented by treatment with 5 mM Ca(NO3)2 in both wild-type and PIP2;5-overexpressing plants. However, 5 µM OA, which was added following NaCl or KF treatment, completely reversed L(p) within several minutes. The results provide evidence for high sensitivity of aquaporin-mediated water transport to relatively low NaCl concentrations and point to the phosphorylation and/or dephosphorylation processes as those that are likely responsible for the protection of L(p) by fluoride and calcium treatments against the effects of NaCl.
authors.affiliation: Department of Renewable Resources, University of Alberta, 442 Earth Sciences Bldg., T6G 2E3, Edmonton, AB, Canada.
authors.forename: Seong H
authors.initials: SH
authors.lastname: Lee
authors.affiliation: Department of Renewable Resources, University of Alberta, 442 Earth Sciences Bldg., T6G 2E3, Edmonton, AB, Canada janusz.zwiazek@ualberta.ca.
authors.forename: Janusz J
authors.initials: JJ
authors.lastname: Zwiazek
mesh_terms: D020346:Aquaporins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport / Q000187:drug effects / Q000235:genetics; D005459:Fluorides / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant; D009997:Osmotic Pressure / Q000187:drug effects; D018517:Plant Roots / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D017680:Potassium Compounds / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D014867:Water / Q000378:metabolism*
chemical_list: D020346:Aquaporins; D029681:Arabidopsis Proteins; D017680:Potassium Compounds; D012333:RNA, Messenger; D014867:Water; C033320:potassium fluoride; D005459:Fluorides
keywords: Aquaporins; Calcium; Cell hydraulic conductivity; Fluoride; NaCl; Okadaic acid