Journal Article

Tissue and Cell-Specific Localization of Rice Aquaporins and Their Water Transport Activities

Junko Sakurai, Arifa Ahamed, Mari Murai, Masayoshi Maeshima and Matsuo Uemura

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 49, issue 1, pages 30-39
Published in print January 2008 | ISSN: 0032-0781
Published online January 2008 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcm162
Tissue and Cell-Specific Localization of Rice Aquaporins and Their Water Transport Activities

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

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Water transport in plants is greatly dependent on the expression and activity of water transport channels, called aquaporins. Here, we have clarified the tissue- and cell-specific localization of aquaporins in rice plants by immunoblotting and immunocytochemistry using seven isoform-specific aquaporin antibodies. We also examined water transport activities of typical aquaporin family members using a yeast expression system in combination with a stopped-flow spectrophotometry assay. OsPIP1 members, OsPIP2;1, OsTIP1;1 and OsTIP2;2 were expressed in both leaf blades and roots, while OsPIP2;3, OsPIP2;5 and OsTIP2;1 were expressed only in roots. In roots, large amounts of aquaporins accumulated in the region adjacent to the root tip (around 1.5–4 mm from the root tip). In this region, cell-specific localization of the various aquaporin members was observed. OsPIP1 members and OsTIP2;2 accumulated predominantly in the endodermis and the central cylinder, respectively. OsTIP1;1 showed specific localization in the rhizodermis and exodermis. OsPIP2;1, OsPIP2;3 and OsPIP2;5 accumulated in all root cells, but they showed higher levels of accumulation in endodermis than other cells. In the region at 35 mm from the root tip, where aerenchyma develops, aquaporins accumulated at low levels. In leaf blades, OsPIP1 members and OsPIP2;1 were localized mainly in mesophyll cells. OsPIP2;1, OsPIP2;3, OsPIP2;5 and OsTIP2;2 expressed in yeast showed high water transport activities. These results suggest that rice aquaporins with various water transport activities may play distinct roles in facilitating water flux and maintaining the water potential in different tissues and cells.

Keywords: Aquaporin; Cell-specific localization; Rice; Water transport activity

Journal Article.  5604 words.  Illustrated.

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

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