Plasma membrane H+-ATPase in the root apex: Evidence for strong expression in xylem parenchyma and asymmetric localization within cortical and epidermal cells

Authors

  • Thomas Jahn,

    1. present address: Plant Physiology/Anatomy Laboratory, Dept of Plant Biology, The Royal Veterinary and Agricultural Univ., Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark
    2. Botanisches Inst. der Univ. Bonn, Venusbergweg 22, D-53115 Bonn, Germany;
    3. corresponding author, e-mail tj@staffkvl.dk
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  • Frantisek Baluska,

    1. Botanisches Inst. der Univ. Bonn, Venusbergweg 22, D-53115 Bonn, Germany;
    2. Inst. of Botany, Slovak Academy of Sciences, Dúbravská cesta 14, 84223 Bratislava, Slovakia;
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  • Wolfgang Michalke,

    1. Inst. für Biologie III, Albert -Ludwigs Univ. Freiburg, Schänzelstraße 1, D-79104 Freiburg, Germany;
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  • Jeffrey F. Harper,

    1. Dept of Cell Biology, The Scripps Research Inst., 10666 North Torry Pines Road, La Jolla, CA 92037, USA.
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  • Dieter Volkmann

    1. Botanisches Inst. der Univ. Bonn, Venusbergweg 22, D-53115 Bonn, Germany;
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Abstract

The cell and subcellular localization of plasma membrane P-type H+-ATPase in root apices from Zea mays L. (maize) seedlings was investigated by immunofluorescence microscopy. H+-ATPase was highly abundant in cells of epidermal and endodermal tissues as well as in phloem companion cells. Strong immunodecoration was also observed in a subset of xylem parenchyma cells forming a connection between the endodermis and metaxylem. Evidence that these cells are equipped for active membrane transport raises the potential that they play a special role in xylem loading. Significant amounts of H+-ATPase were also observed in outer cortical cells. Progressively less H+-ATPase was seen in cortical cells further away from the root-soil interface. The H+-ATPase was asymmetrically localized within both epidermal and outer cortical cells, with higher levels detected on cell surfaces closest to the root-soil interface. This asymmetric localization of H+-ATPase is consistent with the hypothesis that transport systems for uptake of nutrients from the soil are selectively targeted to cell surfaces most exposed to nutrients.

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