MOLECULAR CHARACTERIZATION OF THE NODULATION GENE, NODT, FROM 2 BIOVARS OF RHIZOBIUM-LEGUMINOSARUM

DNA sequencing of the nodlJ region from Rhizobium leguminosarum biovar trifolii revealed the nodT gene immediately downstream of nodJ. DNA hybridizations using a nodT‐specific probe showed that nodT is present in several R. leguminosarum strains. Interestingly, a flavonoid‐inducible nodT gene homologue in R. leguminosarum bv. viciae is not in the nodABCIJ operon but is located downstream of nodMN. The sequence of the nodT gene from bv. viciae was determined and a comparison of the predicted aminoacid sequences of the two nodT genes shows them to be conserved; the predicted protein sequences appear to have a potential transit sequence typical of outer‐membrane proteins. Mutations affecting nodT in either biovar had no observed effect on nodulation of the legumes tested. Copyright © 1990, Wiley Blackwell. All rights reserved