Cloning of a full-length symbiotic hemoglobin cDNA and in situ localization of the corresponding mRNA in Casuarina glauca root nodule


  • This paper is part of the contributions to the Tenth International Conference on Frankia and Actionorhizal Plants jointly sponsored by the college of Agricultural and Environmental Sciences at the University of California at Davis, and the National Science Foundation, held in Davis, CA, USA, 6–11 August, 1995.

D. Bogusz (corresponding author, e-mail

A. Nassar (present address: INRA, Pathologie végétale, F-78026 Versailles Cedex).


We have characterized a full-length cDNA (hb-Cg1F) that represents symbiotic mRNA hemoglobin (hb) from Casuarina glauca root nodules. In situ hybridization was used to examine the correlation between hb-Cg1F mRNA and the state of the Frankia infection process. The efficiency of in situ hybridization using DIG-labeled vs [35S]-labeled probes was compared. The expression of hb-Cg1F gene is induced in young infected host cells prior to the detection of Frankia nifH mRNA. Since Frankia does not form vesicles in C. glauca nodules, it is proposed that Hb is necessary to reduce the O2 concentration in the cytoplasm of the host cells before the nif genes are expressed.