Induction of the Rhizobium fredii nod Box-Independent Nodulation Gene no/J Requires a Functional nodDl Gene. Kyria L. Boundy-Mills. Deparlmenls of Soil Science and Microbiology, University of Minnesota, St. Paul 55108. Renee M. Kosslak(2), Raymond E. Tully(3), Steven G. Pueppke(4) Scott Lohrke(1), and Michael J. Sadowsky(1). (1) Deparlmenls of Soil Science and Microbiology, University of Minnesota, St. Paul 55108; (2) Department of Genetics, Iowa State University, Ames 50011; U.S. (3) Department of Agriculture, ARS, BARC-West, Beltsville, Maryland 20705; and (4) Department of Plant Pathology, University of Missouri, Columbia 65211 U.S.A. MPMI 7:305-308. Accepted 7 December 1993. Copyright 1994 The American Phytopathological Society.

We previously reported the isolation of a flavnnoid-inducible gene from 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 IJSDA 201. We have named this Rene notJ. While the 5' region of nolJ docs not contain a highly conserved nod box consensus sequence, RNA dot blot hybridization analyses indicated that the flavonoid induction of nolJ is dependent on a functional nodDl gene. Our data suggest that transcriptional activation of nolJ occurs by a mechanism different from that proposed for many other nodulation loci.