Environmental and auxin regulation of wood formation involves members of the Aux/IAA gene family in hybrid aspen

Authors

  • Richard Moyle,

    1. Umeå Plant Science Centre, Swedish University of Agricultural Sciences, Department of Forest Genetics and Plant Physiology, 90183 Umeå, Sweden
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    • These authors contributed equally to this work.

  • Jarmo Schrader,

    1. Umeå Plant Science Centre, Swedish University of Agricultural Sciences, Department of Forest Genetics and Plant Physiology, 90183 Umeå, Sweden
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    • These authors contributed equally to this work.

  • Anneli Stenberg,

    1. Umeå Plant Science Centre, Swedish University of Agricultural Sciences, Department of Forest Genetics and Plant Physiology, 90183 Umeå, Sweden
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  • Olof Olsson,

    1. Department of Molecular Biology, Lundberg Laboratory, Göteborg University, 405 30 Göteborg, Sweden
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  • Sangeeta Saxena,

    1. Centre for Plant Molecular Biology, National Botanical Research Institute, 226 001 Lucknow, India
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  • Göran Sandberg,

    1. Umeå Plant Science Centre, Swedish University of Agricultural Sciences, Department of Forest Genetics and Plant Physiology, 90183 Umeå, Sweden
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  • Rishikesh P Bhalerao

    1. Umeå Plant Science Centre, Swedish University of Agricultural Sciences, Department of Forest Genetics and Plant Physiology, 90183 Umeå, Sweden
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*For correspondence (fax +46 90 7865901; e-mail Rishi.Bhalerao@genfys.slu.se).

Summary

Indole acetic acid (IAA/auxin) profoundly affects wood formation but the molecular mechanism of auxin action in this process remains poorly understood. We have cloned cDNAs for eight members of the Aux/IAA gene family from hybrid aspen (Populus tremula L. × Populus tremuloides Michx.) that encode potential mediators of the auxin signal transduction pathway. These genes designated as PttIAA1-PttIAA8 are auxin inducible but differ in their requirement of de novo protein synthesis for auxin induction. The auxin induction of the PttIAA genes is also developmentally controlled as evidenced by the loss of their auxin inducibility during leaf maturation. The PttIAA genes are differentially expressed in the cell types of a developmental gradient comprising the wood-forming tissues. Interestingly, the expression of the PttIAA genes is downregulated during transition of the active cambium into dormancy, a process in which meristematic cells of the cambium lose their sensitivity to auxin. Auxin-regulated developmental reprogramming of wood formation during the induction of tension wood is accompanied by changes in the expression of PttIAA genes. The distinct tissue-specific expression patterns of the auxin inducible PttIAA genes in the cambial region together with the change in expression during dormancy transition and tension wood formation suggest a role for these genes in mediating cambial responses to auxin and xylem development.

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