Isolation of Nodule Specific c-DNA Clones from Medicago sativa

Two nodule specific genes have been isolated from nodule c-DNA clone bank of Medicago sativa using differential hybridization. One of the two genes was leghemoglobin which showed high level of sequence homology to leghemoglobin from other legumes. The second c-DNA gene, nodulin-1 was also sequenced and revealed two direct repeats RA and RB. Repeat RB consists of three tandem copies of 18 amino acids. From the genomic library of Medicago sativa constructed in our lab, nodulin-1 was isolated and partially characterised. The nucleotide sequence showed that this gene contains several introns. The function of nodulin-1 in symbiotic nitrogen fixation is not known at present.