INDUCTION OF THE RHIZOBIUM-FREDII NOD BOX-INDEPENDENT NODULATION GENENOLJ REQUIRES A FUNCTIONAL NODD1 GENE

We previously reported the isolation of a flavonoid-inducible gene fro m the pSym of Rhizobium fredii strain USDA 201 (Sadowsky et al. 1988). In this study, we report that a Tn5 insertion in this gene results in a 6-day delay in the appearance of nodules and a 70% decrease in the number of nodules relative to nodulation by the wild-type R. fredii US DA 201. We have named this gene nolJ. While the 5' region of nolJ does not contain a highly conserved nod box consensus sequence, RNA dot bl ot hybridization analyses indicated that the flavonoid induction of no lJ is dependent on a functional nodD1 gene. Our data suggest that tran scriptional activation of nolJ occurs by a mechanism different from th at proposed for many other nodulation loci.