Planta

, Volume 212, Issue 2, pp 270–278

Expression and distribution of a vacuolar aquaporin in young and mature leaf tissues of Brassica napus in relation to water fluxes

Authors

  • Nathalie Frangne
    • Institut de Botanique, Laboratoire de Physiologie Végétale, Université de Neuchâtel, 2007 Neuchâtel, Switzerland
  • Masayoshi Maeshima
    • Laboratory of Biochemistry, School of Agriculture, Nagoya University, Nagoya 464-01, Japan
  • Anton R. Schäffner
    • Institute of Biochemical Plant Pathology, GSF Research Center for Environment and Health, 85764 Neuherberg-München, Germany
  • Therese Mandel
    • Institute of Plant Physiology, University of Berne, Altenbergrain 21, 3013 Berne, Switzerland
  • Enrico Martinoia
    • Institut de Botanique, Laboratoire de Physiologie Végétale, Université de Neuchâtel, 2007 Neuchâtel, Switzerland
  • Jean-Louis Bonnemain
    • Laboratoire de Physiologie et Biochimie Végétales (ESA CNRS 6161), Université de Poitiers, 86000 Poitiers, France

DOI: 10.1007/s004250000390

Cite this article as:
Frangne, N., Maeshima, M., Schäffner, A. et al. Planta (2001) 212: 270. doi:10.1007/s004250000390

Abstract.

 Recently, it has been shown that water fluxes across biological membranes occur not only through the lipid bilayer but also through specialized water-conducting proteins, the so called aquaporins. In the present study, we investigated in young and mature leaves of Brassica napus L. the expression and localization of a vacuolar aquaporin homologous to radish γ-tonoplast intrinsic protein/vacuolar-membrane integral protein of 23 kDa (TIP/VM 23). In-situ hybridization showed that these tonoplast aquaporins are highly expressed not only in developing but also in mature leaves, which export photosynthates. No substantial differences could be observed between different tissues of young and mature leaves. However, independent of the developmental stage, an immunohistochemical approach revealed that the vacuolar membrane of bundle-sheath cells contained more protein cross-reacting with antibodies raised against radish γ-TIP/VM 23 than the mesophyll cells. The lowest labeling was detected in phloem cells. We compared these results with the distribution of plasma-membrane aquaporins cross-reacting with antibodies detecting a domain conserved among members of the plasma-membrane intrinsic protein 1 (PIP1) subfamily. We observed the same picture as for the vacuolar aquaporins. Furthermore, a high density of gold particles labeling proteins of the PIP1 group could be observed in plasmalemmasomes of the vascular parenchyma. Our results indicate that γ-TIP/VM 23 and PIP1 homologous proteins show a similar expression pattern. Based on these results it is tempting to speculate that bundle-sheath cells play an important role in facilitating water fluxes between the apoplastic and symplastic compartments in close proximity to the vascular tissue.

Key words: Aquaporin localizationBrassica (aquaporin)Plasma membraneVacuolar membraneWater flux

Copyright information

© Springer-Verlag Berlin Heidelberg 2001