Here, a hemoglobin gene from the nitrogen-fixing actinorhizal plant
Myrica gale was isolated, cloned and sequenced. The gene (
MgHb) was a class I hemoglobin with strong sequence homology to non-symbiotic hemoglobin genes.
MgHb is highly expressed in symbiotic root nodules, but transcripts and protein were also detected in leaves of
M. gale. In
Arabidopsis thaliana the
MgHb promoter, linked to a β-glucuronidase coding region, directed expression in the vascular tissue, in shoot meristem and at
root branch point - a pattern very similar to the combined expression pattern of the two non-symbiotic
A. thaliana hemoglobin promoters
AHb1 and
AHb2. The results points to a symbiotic as well as a non-symbiotic specificity of
MgHb similar to a hemoglobin gene identified in
Parasponia andersonii, but different from the situation in
Casuarina glauca - a close actinorhizal relative of
M. gale.
Keywords Evolution - Hemoglobin -
Myrica gale
- Symbiotic
Anne B. Heckmann and Kim H. Hebelstrup contributed
equally to this work