The effects of the loss of TIP1;1 and TIP1;2 aquaporins in Arabidopsis thaliana

Authors

  • Manuela Désirée Schüssler,

    1. Department of Agriculture and Ecology, Faculty of Life Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark
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  • Erik Alexandersson,

    1. Center for Molecular Protein Science, Department of Biochemistry, Lund University, PO Box 124, SE-22100 Lund, Sweden
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  • Gerd Patrick Bienert,

    1. Department of Agriculture and Ecology, Faculty of Life Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark
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  • Thomas Kichey,

    1. Department of Agriculture and Ecology, Faculty of Life Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark
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  • Kristian Holst Laursen,

    1. Department of Agriculture and Ecology, Faculty of Life Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark
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  • Urban Johanson,

    1. Center for Molecular Protein Science, Department of Biochemistry, Lund University, PO Box 124, SE-22100 Lund, Sweden
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  • Per Kjellbom,

    1. Center for Molecular Protein Science, Department of Biochemistry, Lund University, PO Box 124, SE-22100 Lund, Sweden
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  • Jan Kofod Schjoerring,

    1. Department of Agriculture and Ecology, Faculty of Life Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark
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  • Thomas Paul Jahn

    Corresponding author
    1. Department of Agriculture and Ecology, Faculty of Life Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark
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(fax +45 353 33460; e-mail tpj@life.ku.dk).

Summary

Loss of aquaporin TIP1;1 in Arabidopsis has been suggested to result in early senescence and plant death. This was based on the fact that a partial reduction of TIP1;1 by RNA interference (RNAi) led to gradual phenotypes, ranging from indistinguishable from wild type to lethality, depending on the degree of downregulation of the target messenger, and displaying pleiotropic effects in primary metabolism and cell signalling. A hypothesis was put forward to suggest that TIP1;1, apart from its transport function, may play an essential role in vesicle routing. Here we identify an Arabidopsis transposon insertion line tip1;1-1 that is completely devoid of TIP1;1 protein, as demonstrated by western blotting and immunolocalization using an isoform-specific antibody. Strikingly, the complete absence of the protein did not result in any significant effect on metabolism or elemental composition of the plants. Microarray analysis did not indicate increased expression of other aquaporins to compensate for the lack of TIP1;1 in tip1;1-1. We further developed a double mutant of TIPs in Arabidopsis, lacking both TIP1;1 and its closest paralog TIP1;2. Arabidopsis mutants lacking both TIP1;1 and TIP1;2 showed a minor increase in anthocyanin content, and a reduction in catalase activity, but showed no changes in water status. In contrast to earlier reports, plants lacking TIP1;1 and TIP1;2 aquaporins are alive and thriving. We suggest that RNAi directed towards TIP1;1 may have resulted in off-target gene silencing, a notion that is potentially interesting for various studies analysing gene function by RNAi.

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