Plant biol (Stuttg) 2007; 9(6): 776-785
DOI: 10.1055/s-2007-965258
Research Paper

Georg Thieme Verlag Stuttgart KG · New York

Truncated Hemoglobins in Actinorhizal Nodules of Datisca glomerata

K. Pawlowski1 , 2 , 6 , K. R. Jacobsen3 , N. Alloisio4 , R. Ford Denison3 , 7 , M. Klein3 , 8 , J. D. Tjepkema5 , T. Winzer1 , A. Sirrenberg1 , 9 , C. Guan2 , 10 , A. M. Berry3
  • 1Albrecht von Haller Institute for Plant Sciences, Department of Plant Biochemistry, Göttingen University, 37077 Göttingen, Germany
  • 2Department of Molecular Biology, Wageningen University, 6703 HA Wageningen, The Netherlands
  • 3Department of Plant Sciences, University of California, Davis, CA 95616, USA
  • 4Laboratoire d'Ecologie Microbienne, UMR CNRS 5557, Université Claude Bernard Lyon 1, 69622 Villeurbanne Cedex, France
  • 5Department of Biological Sciences, University of Maine, Orono, ME 04469-5722, USA
  • 6Present address: Department of Botany, Stockholm University, 10691 Stockholm, Sweden
  • 7Present address: Ecology, Evolution, and Behavior, University of Minnesota, St. Paul, MN 55108, USA
  • 8Present address: Department of Plant Biology, Cornell University, Ithaca, NY 14850, USA
  • 9Present address: Molecular Phytopathology, Göttingen University, 37077 Göttingen, Germany
  • 10Present address: Department of Plant Pathology, University of Wisconsin-Madison, Madison, WI 53706, USA
Further Information

Publication History

Received: November 2, 2006

Accepted: March 28, 2007

Publication Date:
07 August 2007 (eFirst)

Abstract

Three types of hemoglobins exist in higher plants, symbiotic, non-symbiotic, and truncated hemoglobins. Symbiotic (class II) hemoglobins play a role in oxygen supply to intracellular nitrogen-fixing symbionts in legume root nodules, and in one case (Parasponia sp.), a non-symbiotic (class I) hemoglobin has been recruited for this function. Here we report the induction of a host gene, dgtrHb1, encoding a truncated hemoglobin in Frankia-induced nodules of the actinorhizal plant Datisca glomerata. Induction takes place specifically in cells infected by the microsymbiont, prior to the onset of bacterial nitrogen fixation. A bacterial gene (Frankia trHbO) encoding a truncated hemoglobin with O2-binding kinetics suitable for the facilitation of O2 diffusion ([Tjepkema et al., 2002]) is also expressed in symbiosis. Nodule oximetry confirms the presence of a molecule that binds oxygen reversibly in D. glomerata nodules, but indicates a low overall hemoglobin concentration suggesting a local function. Frankia TrHbO is likely to be responsible for this activity. The function of the D. glomerata truncated hemoglobin is unknown; a possible role in nitric oxide detoxification is suggested.