NOVEL, HIGHLY EXPRESSED LATE NODULIN GENE (LJNOD16) FROM LOTUS-JAPONICUS

We have isolated a Lotus japonicus cDNA corresponding to a highly abun dant, late nodule-specific RNA species that encodes a polypeptide with a predicted molecular mass of 15.6 kD. The protein and its correspond ing gene were designated Nlj16 and LjNOD16, respectively. LjNOD16 was found to be expressed only in the infected cells of L. japonicus nodul es. Related DNA sequences could be identified in the genomes of both G lycine max and Medicago sativa. In the latter, a homologous mRNA speci es was detected in the nodules. Unlike LjNOD16, its alfalfa homologs a ppear to represent low-abundance mRNA species. However, the proteins c orresponding to the LjNOD16 and its alfalfa homolog could be detected at similar levels in nodules but not in roots of both legume species. The predicted amino acid sequence analysis of nodulin Nlj16 revealed t he presence of a long alpha-helical region and a positively charged C terminus. The former domain has a very high propensity to form a coile d-coil type structure, indicating that nodulin Nlj16 may interact with an as-yet-unidentified protein target(s) in the nodule-infected cells . Homology searches revealed no significant similarities to any known sequences in the databases, with the exception of two related, anonymo us Arabidopsis expressed sequence tags.