Article
- The EMBO Journal (1999) 18, 2066 - 2073
- doi:10.1093/emboj/18.8.2066
AUX1 regulates root gravitropism in Arabidopsis by facilitating auxin uptake within root apical tissues
Alan Marchant1, Joanna Kargul1,2, Sean T. May1, Philippe Muller3, Alain Delbarre3, Catherine Perrot-Rechenmann3 and Malcolm J. Bennett1
- Division of Plant Sciences, School of Biological Sciences, University of Nottingham, NG7 2RD, UK
- Present address: Laboratory of Plant Physiology and Biophysics, Wye College, University of London, Ashford, TN25 5AH, UK
- Institut des Sciences Végétales, CNRS, 91198 Gif-sur-Yvette Cedex, France
Correspondence to:
Malcolm J. Bennett, E-mail: malcolm.bennett@nottingham.ac.uk
Received 20 October 1998; Accepted 24 February 1999; Revised 24 February 1999
Abstract
Plants employ a specialized transport system composed of separate influx and efflux carriers to mobilize the plant hormone auxin between its site(s) of synthesis and action. Mutations within the permease-like AUX1 protein significantly reduce the rate of carrier-mediated auxin uptake within Arabidopsis roots, conferring an agravitropic phenotype. We are able to bypass the defect within auxin uptake and restore the gravitropic root phenotype of aux1 by growing mutant seedlings in the presence of the membrane-permeable synthetic auxin, 1-naphthaleneacetic acid. We illustrate that AUX1 expression overlaps that previously described for the auxin efflux carrier, AtPIN2, using transgenic lines expressing an AUX1 promoter::uidA (GUS) gene. Finally, we demonstrate that AUX1 regulates gravitropic curvature by acting in unison with the auxin efflux carrier to co-ordinate the localized redistribution of auxin within the Arabidopsis root apex. Our results provide the first example of a developmental role for the auxin influx carrier within higher plants and supply new insight into the molecular basis of gravitropic signalling.
Keywords:
- Arabidopsis,
- AUX1,
- auxin,
- gravitropism,
- transport
