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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 HgCl2, which is a typical water channel inhibitor. This activity was not modified by some inhibitors against protein kinase and protein phosphatase.
Keywords: Keywords: Aquaporin — Barley — Competitive RT-PCR — Salt stress.; Abbreviations: DTT, dithiothreitol; DMSO, dimethylsulfoxide; IBMX, 3-isobutyle-1-methylxanthine; MBS, modified Barth’s solution; Pf, Osmotic water permeability; PIP, Plasma membrane Intrinsic Protein; PIPES, piperazine-N,N′-bis(2-ethanesulfonic acid); PMSF, phenylmethylsulfonylfluoride; RACE, rapid amplification of cDNA end; RT-PCR, reverse transcription-PCR; TIP, Tonoplast Intrinsic Protein.
Journal Article. 5497 words. Illustrated.
Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry
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