Ectopic expression of Arabidopsis thaliana plasma membrane intrinsic protein 2 aquaporins in lily pollen increases the plasma membrane water permeability of grain but not of tube protoplasts

Authors

  • Aniela Sommer,

    1. Molecular Plant Biophysics and Biotechnology, Department of Molecular Biology, University of Salzburg, Billrothstr. 11, 5020 Salzburg, Austria;
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  • Birgit Geist,

    1. Institute of Biochemical Plant Pathology, Helmholtz Zentrum München – German Research Center for Environmental Health (GmbH), 85764 Neuherberg, Germany
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  • Olivier Da Ines,

    1. Institute of Biochemical Plant Pathology, Helmholtz Zentrum München – German Research Center for Environmental Health (GmbH), 85764 Neuherberg, Germany
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  • Renate Gehwolf,

    1. Molecular Plant Biophysics and Biotechnology, Department of Molecular Biology, University of Salzburg, Billrothstr. 11, 5020 Salzburg, Austria;
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  • Anton R. Schäffner,

    1. Institute of Biochemical Plant Pathology, Helmholtz Zentrum München – German Research Center for Environmental Health (GmbH), 85764 Neuherberg, Germany
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  • Gerhard Obermeyer

    1. Molecular Plant Biophysics and Biotechnology, Department of Molecular Biology, University of Salzburg, Billrothstr. 11, 5020 Salzburg, Austria;
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Author for correspondence:
Gerhard Obermeyer
Tel: +43(0)662 8044 7230
Fax: +43(0)662 8044 7209
Email: gerhard.obermeyer@sbg.ac.at

Summary

  • • To investigate the role of aquaporin-mediated water transport during pollen grain germination and tube growth, Arabidopsis thaliana plasma membrane intrinsic proteins (PIPs) were expressed in pollen of Lilium longiflorum (lily).
  • • Successful expression of AtPIPs in particle-bombarded lily pollen grains was monitored by co-expression with fluorescent proteins and single-cell RT-PCR, and by measuring the water permeability coefficient (Pos) in swelling assays using protoplasts prepared from transformed pollen grains and tubes.
  • • Expression of AtPIP1;1 and AtPIP1;2 in pollen grains resulted in Pos values similar to those measured in nontransformed pollen grain protoplasts (6.65 ± 2.41 µm s−1), whereas expression of AtPIP2 significantly increased Pos (AtPIP2;1, 13.79 ± 6.38; AtPIP2;2, 10.16 ± 3.30 µm s−1). Transformation with combinations of AtPIP1 and AtPIP2 did not further enhance Pos. Native pollen tube protoplasts showed higher Pos values (13.23 ± 4.14 µm s−1) than pollen grain protoplasts but expression of AtPIP2;1 (18.85 ± 7.60 µm s−1) did not significantly increase their Pos values. Expression of none of the tested PIPs had any effect on pollen tube growth rates.
  • • The ectopic expression of AtPIP2s in lily pollen increased the water permeability of the plasma membrane in pollen grains, but not in pollen tubes. The measured endogenous water permeability does not limit water uptake during tube growth, but has to be regulated to prevent tube bursting.

Ancillary