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  • The EMBO Journal (2004) 23, 572 - 581
  • doi:10.1038/sj.emboj.7600068

Published online: 29 January 2004

A protein kinase target of a PDK1 signalling pathway is involved in root hair growth in Arabidopsis

Richard G Anthony1, Rossana Henriques1, Anne Helfer1, Tamás Mészáros1, Gabino Rios2, Christa Testerink3, Teun Munnik3, Maria Deák4, Csaba Koncz2 and László Bögre1

  1. School of Biological Sciences, Royal Holloway, University of London, Egham, Surrey, UK
  2. Max-Planck Institut für Züchtungsforschung Carl-von-Linné-Weg 10, Köln, Germany
  3. Department of Plant Physiology, Swammerdam Institute for Life Sciences (SILS), University of Amsterdam, Netherlands
  4. MRC Protein Phosphorylation Unit, University of Dundee, Dow Street, Dundee, UK

Correspondence to:

László Bögre, School of Biological Sciences, Royal Holloway, University of London, Egham TW20 0EX, UK. Tel.: +44 1784 443407; Fax: +44 1784 434326; E-mail: l.bogre@rhul.ac.uk

Received 26 May 2003; Accepted 15 December 2003

Here we report on a lipid-signalling pathway in plants that is downstream of phosphatidic acid and involves the Arabidopsis protein kinase, AGC2-1, regulated by the 3'-phosphoinositide-dependent kinase-1 (AtPDK1). AGC2-1 specifically interacts with AtPDK1 through a conserved C-terminal hydrophobic motif that leads to its phosphorylation and activation, whereas inhibition of AtPDK1 expression by RNA interference abolishes AGC2-1 activity. Phosphatidic acid specifically binds to AtPDK1 and stimulates AGC2-1 in an AtPDK1-dependent manner. AtPDK1 is ubiquitously expressed in all plant tissues, whereas expression of AGC2-1 is abundant in fast-growing organs and dividing cells, and activated during re-entry of cells into the cell cycle after sugar starvation-induced G1-phase arrest. Plant hormones, auxin and cytokinin, synergistically activate the AtPDK1-regulated AGC2-1 kinase, indicative of a role in growth and cell division. Cellular localisation of GFP-AGC2-1 fusion protein is highly dynamic in root hairs and at some stages confined to root hair tips and to nuclei. The agc2-1 knockout mutation results in a reduction of root hair length, suggesting a role for AGC2-1 in root hair growth and development.

  • Keywords:

    • AGC kinase,
    • growth signalling,
    • lipid signalling,
    • PDK1,
    • phosphatidic acid,
    • root hair elongation