Journal Article

Mechanisms of Water Transport Mediated by PIP Aquaporins and Their Regulation Via Phosphorylation Events Under Salinity Stress in Barley Roots

Tomoaki Horie, Toshiyuki Kaneko, Genki Sugimoto, Shizuka Sasano, Sanjib Kumar Panda, Mineo Shibasaka and Maki Katsuhara

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 52, issue 4, pages 663-675
Published in print April 2011 | ISSN: 0032-0781
Published online March 2011 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcr027
Mechanisms of Water Transport Mediated by PIP Aquaporins and Their Regulation Via Phosphorylation Events Under Salinity Stress in Barley Roots

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  • Biochemistry
  • Molecular and Cell Biology
  • Plant Sciences and Forestry

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Water homeostasis is crucial to the growth and survival of plants under water-related stress. Plasma membrane intrinsic proteins (PIPs) have been shown to be primary channels mediating water uptake in plant cells. Here we report the water transport activity and mechanisms for the regulation of barley (Hordeum vulgare) PIP aquaporins. HvPIP2 but not HvPIP1 channels were found to show robust water transport activity when expressed alone in Xenopus laevis oocytes. However, the co-expression of HvPIP1 with HvPIP2 in oocytes resulted in significant increases in activity compared with the expression of HvPIP2 alone, suggesting the participation of HvPIP1 in water transport together with HvPIP2 presumably through heteromerization. Severe salinity stress (200 mM NaCl) significantly reduced root hydraulic conductivity (Lpr) and the accumulation of six of 10 HvPIP mRNAs. However, under relatively mild stress (100 mM NaCl), only a moderate reduction in Lpr with no significant difference in HvPIP mRNA levels was observed. Sorbitol-mediated osmotic stress equivalent to 100 and 200 mM NaCl induced nearly identical Lpr reductions in barley roots. Furthermore, the water transport activity in intact barley roots was suggested to require phosphorylation that is sensitive to a kinase inhibitor, staurosporine. HvPIP2s also showed water efflux activity in Xenopus oocytes, suggesting a potential ability to mediate water loss from cells under hypertonic conditions. Water transport via HvPIP aquaporins and the significance of reductions of Lpr in barley plants during salinity stress are discussed.

Keywords: Aquaporin; Barley; Plasma membrane intrinsic proteins (PIPs); Root hydraulic conductivity; Salinity stress; Water transport

Journal Article.  7748 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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