Functional analysis of water channels in barley roots.
We identified three genes homologous to water channels in the plasma membrane type subfamily from roots of barley seedlings. These genes were designated HvPIP2;1, HvPIP1;3, and HvPIP1;5 after comparison to Arabidopsis aquaporins. Competitive reverse transcription (RT)-PCR was applied in order to distinguish and to quantify their transcripts. The HvPIP2;1 transcript was the most abundant among the three in roots. Salt stress (200 mM NaCl) down-regulated HvPIP2;1 (transcript and protein), but had almost no effect on the expressions of HvPIP1;3, or HvPIP1;5. Approximately equal amounts of the transcripts of the three were detected in shoots, and salt stress enhanced the expression of HvPIP2;1 but not of HvPIP1;3, or HvPIP1;5. HvPIP2;1 protein was confirmed to be localized in the plasma membrane. Functional expression of HvPIP2;1 in Xenopus oocytes confirmed that HvPIP2;1 encoded an aquaporin that transports water. This water permeability was reduced by HgCl(2), which is a typical water channel inhibitor. This activity was not modified by some inhibitors against protein kinase and protein phosphatase.
Research Institute for Bioresources, Okayama University, Kurashiki, 710-0046 Japan. kmaki@rib.okayama-u.ac.jp
Maki
M
Katsuhara
Yoshiko
Y
Akiyama
Kazuki
K
Koshio
Mineo
M
Shibasaka
Kunihiro
K
Kasamo
D000222:Adaptation, Physiological / Q000235:genetics / Q000502:physiology; D000465:Algorithms; D000595:Amino Acid Sequence; D000818:Animals; D020346:Aquaporins / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000502:physiology; D029681:Arabidopsis Proteins; D002227:Carbazoles / Q000494:pharmacology; D002462:Cell Membrane / Q000378:metabolism; D002463:Cell Membrane Permeability / Q000187:drug effects; D018076:DNA, Complementary / Q000235:genetics / Q000378:metabolism; D005260:Female; D018506:Gene Expression Regulation, Plant; D001467:Hordeum / Q000187:drug effects / Q000235:genetics* / Q000502:physiology; D026121:Indole Alkaloids; D007473:Ion Channels / Q000235:genetics; D008627:Mercuric Chloride / Q000494:pharmacology; D008969:Molecular Sequence Data; D019319:Okadaic Acid / Q000494:pharmacology; D009865:Oocytes / Q000502:physiology; D009997:Osmotic Pressure / Q000187:drug effects; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors; D010766:Phosphorylation; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D018517:Plant Roots / Q000187:drug effects / Q000235:genetics* / Q000502:physiology; D047428:Protein Kinase Inhibitors; D017386:Sequence Homology, Amino Acid; D012965:Sodium Chloride / Q000494:pharmacology; D014867:Water / Q000494:pharmacology / Q000502:physiology; D014982:Xenopus laevis
D020346:Aquaporins; D029681:Arabidopsis Proteins; D002227:Carbazoles; D018076:DNA, Complementary; D026121:Indole Alkaloids; D007473:Ion Channels; D010940:Plant Proteins; D047428:Protein Kinase Inhibitors; C110065:major intrinsic protein, plant; C491680:plasma membrane intrinsic protein 2 Arabidopsis; D014867:Water; D019319:Okadaic Acid; D012965:Sodium Chloride; D008627:Mercuric Chloride; C049985:staurosporine aglycone; D010749:Phosphoprotein Phosphatases