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Vol. 156, No. 3JOURNAL OF BACTERIOLOGY, Dec. 1983, p. 1025-1034 0021-9193/83/121025-10$02.00/0
 

Summary: Vol. 156, No. 3JOURNAL OF BACTERIOLOGY, Dec. 1983, p. 1025-1034
0021-9193/83/121025-10$02.00/0
Copyright C 1983, American Society for Microbiology
Molecular Characterization of Tn5-Induced Symbiotic (Fix-)
Mutants of Rhizobium meliloti
J. LYNN ZIMMERMAN,t WYNNE W. SZETO4 AND FREDERICK M. AUSUBELW*
Department ofCellular and Developmental Biology, Harvard University, Cambridge, Massachusetts 02138
Received 11 July 1983/Accepted 12 September 1983
To investigate the expression of specific symbiotic genes during the develop-
ment of nitrogen-fixing root nodules, we conducted a systematic analysis of
nodule-specific proteins and RNAs produced after the inoculation of alfalfa roots
with a series ofRhizobium meliloti mutants generated by site-directed transposon
TnS mutagenesis. The mutagenized region ofthe Rhizobium genome covered -10
kilobases and included the region encoding the nitrogenase polypeptides. All
mutant strains that were analyzed produced nodules, but with several strains the
nodules failed to fix nitrogen (Nod' Fix- phenotype). All Fix- nodules accumu-
lated reduced levels of the host plant protein leghemoglobin. In addition, TnS
insertions in the nitrogenase operon (nifHDK genes) eliminated some or all of the
nitrogenase polypeptides and nifHDK RNA transcripts, depending on the site of
insertion. Finally, mutation of a region -5 kilobases upstream from the nitroge-

  

Source: Ausubel, Frederick M. - Department of Genetics, Harvard University

 

Collections: Biology and Medicine