The gibberellin biosynthetic genes AtGA20ox1 and AtGA20ox2 act, partially redundantly, to promote growth and development throughout the Arabidopsis life cycle

Authors

  • Ivo Rieu,

    1. Plant Science Department, Rothamsted Research, Harpenden, Hertfordshire AL5 2JQ, UK
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    • Present address: Laboratory of Molecular Genetics and Biotechnology of Plants, University of Freiburg, 79 104 Freiburg, Germany.

  • Omar Ruiz-Rivero,

    1. Plant Science Department, Rothamsted Research, Harpenden, Hertfordshire AL5 2JQ, UK
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    • Present address: Instituto de Biología Molecular y Celular de Plantas (IBMCP), Universidad Politécnica de Valencia-CSIC, Avda de los Naranjos s/n, 46022 Valencia, Spain.

  • Nieves Fernandez-Garcia,

    1. Plant Science Department, Rothamsted Research, Harpenden, Hertfordshire AL5 2JQ, UK
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    • §

      Present address: CEBAS-CSIC, PO Box 164, 30100 Espinardo, Murcia, Spain.

  • Jayne Griffiths,

    1. Plant Science Department, Rothamsted Research, Harpenden, Hertfordshire AL5 2JQ, UK
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    • Present address: CSIRO Plant Industry, Canberra, ACT 2601, Australia.

  • Stephen J. Powers,

    1. Biomathematics and Bioinformatics Department, Rothamsted Research, Harpenden, Hertfordshire AL5 2JQ, UK
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  • Fan Gong,

    1. Plant Science Department, Rothamsted Research, Harpenden, Hertfordshire AL5 2JQ, UK
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  • Terezie Linhartova,

    1. Plant Science Department, Rothamsted Research, Harpenden, Hertfordshire AL5 2JQ, UK
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    • **

      Present address: Palacky University & Institute of Experimental Botany, ASCR Slechtitelu 11, 783 71 Olomouc, Czech Republic.

  • Sven Eriksson,

    1. Umeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, S-90183 Umeå, Sweden
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  • Ove Nilsson,

    1. Umeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, S-90183 Umeå, Sweden
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  • Stephen G. Thomas,

    1. Plant Science Department, Rothamsted Research, Harpenden, Hertfordshire AL5 2JQ, UK
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  • Andrew L. Phillips,

    1. Plant Science Department, Rothamsted Research, Harpenden, Hertfordshire AL5 2JQ, UK
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  • Peter Hedden

    Corresponding author
    1. Plant Science Department, Rothamsted Research, Harpenden, Hertfordshire AL5 2JQ, UK
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(fax +44 1582 763010; e-mail peter.hedden@bbsrc.ac.uk).

Summary

The activity of the gibberellin (GA) biosynthetic enzymes GA 20-oxidases (GA20ox) is of particular importance in determining GA concentration in many plant species. In Arabidopsis these enzymes are encoded by a family of five genes: AtGA20ox1AtGA20ox5. Transcript analysis indicated that they have different expression patterns and may thus participate differentially in GA-regulated developmental processes. We have used reverse genetics to determine the physiological roles of AtGA20ox1 and AtGA20ox2, the most highly expressed GA20ox genes during vegetative and early reproductive development. AtGA20ox1 and AtGA20ox2 act redundantly to promote hypocotyl and internode elongation, flowering time, elongation of anther filaments, the number of seeds that develop per silique and elongation of siliques, with AtGA20ox1 making the greater contribution to internode and filament elongation, and AtGA20ox2 making the greater contribution to flowering time and silique length. Pollination of the double mutant with wild-type pollen indicated that the GA promoting silique elongation is of maternal origin. The ga20ox2 phenotype revealed that GA promotes the number of stem internodes that elongate upon bolting, and does so independently of its effect on internode elongation. Comparison of the phenotype of the double mutant with that of the highly GA-deficient ga1-3 mutant indicates that other GA20ox genes contribute to all the developmental processes examined, and, in some cases such as root growth and leaf expansion, make major contributions, as these processes were unaffected in the double mutant. In addition, the effects of the mutations are mitigated by the homeostatic mechanism that acts on expression of other GA dioxygenase and GID1 receptor genes.

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