Abstract
Root nodules of some non-leguminous woody plants fix atmospheric nitrogen to assimilate for plant nutrition in symbiosis with the actinomycetes Frankia , so-called actinorhizal plants (ex. Alnus, Elaegnus, Casuarina ).
In leguminous plants, a nodule specific protein, leghemoglobin, is synthesized and sufficiently accumulated in nodules and closely related to nitrogen fixing activity. The hemoglobin genes in the actinorhizal plant (Casuarina) have been identified and they are grouped into two clusters, symbiotic type and non-symbiotic type.
In this study, two hemoglobin-like genes (AfNhb1, AfNhb2) were isolated from the cDNA library of A. firma nodules by plaque hybridization method. Deduced amino acid sequences suggested that these genes were classified into the non-symbiotic hemoglobin cluster and similarity was 100%. Results from RT-PCR analysis, predominant expression of AfNhb1 and AfNhb2 was determined in the nodules and leaves, respectively. In addition, these genes also were investigated the expression against various stress treatments.
