Planta

, Volume 224, Issue 1, pp 133–144

The diageotropica gene of tomato encodes a cyclophilin: a novel player in auxin signaling

  • KwangChul Oh
  • Maria G. Ivanchenko
  • T. J. White
  • Terri L. Lomax
Original Article

DOI: 10.1007/s00425-005-0202-z

Cite this article as:
Oh, K., Ivanchenko, M.G., White, T.J. et al. Planta (2006) 224: 133. doi:10.1007/s00425-005-0202-z

Abstract

The single gene, auxin-resistant diageotropica (dgt) mutant of tomato displays a pleiotropic auxin-related phenotype that includes a slow gravitropic response, lack of lateral roots, reduced apical dominance, altered vascular development, and reduced fruit growth. Some auxin responses are unaltered in dgt plants, however, and the levels, metabolism, and transport of auxin appear normal, indicating that the Dgt gene encodes a component of a specific auxin signaling pathway. By combining map-based cloning with comparative microsynteny, we determined that the Dgt gene encodes a cyclophilin (CYP) (LeCYP1; gi:170439) that has not previously been identified as a component of auxin signaling and plant development. Each of the three known dgt alleles contains a unique mutation in the coding sequence of LeCyp1. Alleles dgt1-1and dgt1-2 contain single nucleotide point mutations that generate an amino acid change (G137R) and a stop codon (W128stop), respectively, while dgtdp has an amino acid change (W128CΔ129–133) preceding a 15 bp deletion. Complementation of dgt plants with the wild-type LeCyp1 gene restored the wild-type phenotype. Each dgt mutation reduced or nullified the peptidyl–prolyl isomerase activity of the GST–LeCYP1 fusion proteins in vitro. RT-PCR and immunoblot analyses indicated that the dgt mutations do not affect the expression of LeCyp1 mRNA, but the accumulation of LeCYP1 protein is greatly reduced for all three mutant alleles. The CYP inhibitor, cyclosporin A, partially mimics the effects of the dgt mutation in inhibiting auxin-induced adventitious root initiation in tomato hypocotyl sections and reducing the auxin-induced expression of the early auxin response genes, LeIAA10 and 11. These observations confirm that the PPIase activity of the tomato CYP, LeCYP1, encoded by the Dgt gene is important for specific aspects of auxin regulation of plant growth, development, and environmental responses.

Keywords

DiageotropicaCyclophilinCyclosporin AMap-based cloningMicrosyntenyAuxin

Abbreviations

dgt

diageotropica

CYP

Cyclophilin

CsA

Cyclosporin A

1-NAA

α-Napthaleneacetic acid

PPIase

Peptidyl–prolyl isomerase

Copyright information

© Springer-Verlag 2005

Authors and Affiliations

  • KwangChul Oh
    • 1
    • 2
  • Maria G. Ivanchenko
    • 1
  • T. J. White
    • 1
  • Terri L. Lomax
    • 1
    • 3
  1. 1.Department of Botany and Plant Pathology and the Center for Gene Research and BiotechnologyOregon State UniversityCorvallisUSA
  2. 2.Plant Gene Expression Center, Department of Plant and Microbial BiologyUniversity of California BerkeleyAlbanyUSA
  3. 3.Exploration Systems Mission DirectorateNASA HeadquartersWashingtonUSA