AtEXO70A1, a member of a family of putative exocyst subunits specifically expanded in land plants, is important for polar growth and plant development

Authors

  • Lukáš Synek,

    1. Institute of Experimental Botany, Academy of Sciences of the Czech Republic, Rozvojova 135, 165 00 Prague 6, Czech Republic,
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  • Nicole Schlager,

    1. Institute of Applied Genetics and Cell Biology, BOKU – University of Natural Resources and Applied Life Sciences, Muthgasse 18, A-1190 Vienna, Austria, and
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  • Marek Eliáš,

    1. Department of Plant Physiology, Faculty of Sciences, Charles University, Vinicna 5, 128 44 Prague 2, Czech Republic
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  • Michaël Quentin,

    1. Institute of Experimental Botany, Academy of Sciences of the Czech Republic, Rozvojova 135, 165 00 Prague 6, Czech Republic,
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  • Marie-Theres Hauser,

    1. Institute of Applied Genetics and Cell Biology, BOKU – University of Natural Resources and Applied Life Sciences, Muthgasse 18, A-1190 Vienna, Austria, and
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  • Viktor Žárský

    Corresponding author
    1. Institute of Experimental Botany, Academy of Sciences of the Czech Republic, Rozvojova 135, 165 00 Prague 6, Czech Republic,
    2. Department of Plant Physiology, Faculty of Sciences, Charles University, Vinicna 5, 128 44 Prague 2, Czech Republic
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*For correspondence (fax +420 225 106 461; phone +420 225 106 457; e-mail: zarsky@ueb.cas.cz).

Summary

The exocyst is a hetero-oligomeric protein complex involved in exocytosis and has been extensively studied in yeast and animal cells. Evidence is now accumulating that the exocyst is also present in plants. Bioinformatic analysis of genes encoding plant homologs of the exocyst subunit, Exo70, revealed that three Exo70 subgroups are evolutionarily conserved among angiosperms, lycophytes and mosses. Arabidopsis and rice contain 22 and approximately 39 EXO70 genes, respectively, which can be classified into nine clusters considered to be ancient in angiosperms (one has been lost in Arabidopsis). We characterized two independent T-DNA insertional mutants of the AtEXO70A1 gene (exo70A1-1 and exo70A1-2). Heterozygous EXO70A1/exo70A1 plants appear to be normal and segregate in a 1:2:1 ratio, suggesting that neither male nor female gametophytes are affected by the EXO70A1 disruption. However, both exo70A1-1 and exo70A1-2 homozygotes exhibit an array of phenotypic defects. The polar growth of root hairs and stigmatic papillae is disturbed. Organs are generally smaller, plants show a loss of apical dominance and indeterminate growth where instead of floral meristems new lateral inflorescences are initiated in a reiterative manner. Both exo70A1 mutants have dramatically reduced fertility. These results suggest that the putative exocyst subunit EXO70A1 is involved in cell and organ morphogenesis.

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