Characterization of a nodM/glmS homologous gene in the symbiotic cyanobacterium Nostoc PCC 9229

A nodM/glmS homologue was identified by PCR in Nostoc PCC 9229, a cyanobact erial strain forming symbiosis with Gunnera plants, and the corresponding g ene was isolated and sequenced. The predicted amino acid sequence shows sig nificant homology (40% to 67% identity) to other bacterial glutamine-fructo se-6-P-aminotransferases. The gene is present as a single copy in the genom e of the Nostoc PCC 9229 as well as in other symbiotic and free-living cyan obacteria. Initial data indicate that the isolated gene is linked to the ps aC gene and that there is no evidence for the presence of a nod genes clust er organized as in rhizobia. RNAse protection assays did not show any induc tion in the expression pattern of the gene by Gunnera plant mucilage, seed rinse extract or different flavonoids. These data suggest that the nodM hom ologue in Nostoc should be considered as a glmS housekeeping gene which doe s not play an immediate role in the Nostoc-Gunnera symbiosis. The nucleotid e sequence data reported in this paper has been deposited in GenBank (acces sion number AF028734).