Journal Article

Identification of 33 Rice Aquaporin Genes and Analysis of Their Expression and Function

Junko Sakurai, Fumiyoshi Ishikawa, Tomoya Yamaguchi, Matsuo Uemura and Masayoshi Maeshima

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 46, issue 9, pages 1568-1577
Published in print September 2005 | ISSN: 0032-0781
Published online September 2005 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pci172
Identification of 33 Rice Aquaporin Genes and Analysis of Their Expression and Function

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

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Plant aquaporins form a large protein family including plasma membrane-type (PIPs) and tonoplast-type aquaporins (TIPs), and facilitate osmotic water transport across membranes as a key physiological function. We identified 33 genes for aquaporins in the genome sequence of rice (Oryza sativa L. cv. Nipponbare). We investigated their expression levels in leaf blades, roots and anthers of rice (cv. Akitakomachi) using semi-quantitative reverse transcription–PCR (RT–PCR). At both early tillering (21 d after germination) and panicle formation (56 d) stages, six genes, including OsPIP2;4 and OsPIP2;5, were expressed predominantly in roots, while 14 genes, including OsPIP2;7 and OsTIP1;2, were found in leaf blades. Eight genes, such as OsPIP1;1 and OsTIP4;1, were evenly expressed in leaf blades, roots and anthers. Analysis by stopped-flow spectrophotometry revealed high water channel activity when OsPIP2;4 or OsPIP2;5 were expressed in yeast but not when OsPIP1;1 or OsPIP1;2 were expressed. Furthermore, the mRNA levels of OsPIP2;4 and OsPIP2;5 showed a clear diurnal fluctuation in roots; they showed a peak 3 h after the onset of light and dropped to a minimum 3 h after the onset of darkness. The mRNA levels of 10 genes including OsPIP2;4 and OsPIP2;5 markedly decreased in roots during chilling treatment and recovered after warming. The changes in mRNA levels during and after the chilling treatment were comparable with that of the bleeding sap volume. These results suggested the relationship between the root water uptake and mRNA levels of several aquaporins with high water channel activity, such as OsPIP2;4 and OsPIP2;5.

Keywords: Aquaporin; Gene expression; Rice; Water permeability; NIP, Nod26-like intrinsic protein; PIP, plasma membrane intrinsic protein; RT–PCR, reverse transcription–PCR; SIP, small and basic intrinsic protein; TIP, tonoplast intrinsic protein

Journal Article.  5882 words.  Illustrated.

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

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