Many bacteria establish pathogenic or symbiotic interactions with higher organisms. We study the nutritionally mutualistic interaction or Rhizobium meliloti with a host legume, alfalfa. This host-microbe association proceeds by a ordered series of steps, which are unique and are highly specific to the interaction of particular species. The early steps of the interaction are controlled by a series of bacterial nodulation (nod) genes, whose expression is induced by a small flavonoid compound, luteolin, produced by the host. In addition, induction of nod genes depends on a protein, NodD. In R. meliloti, three nodD genes encode regulatory proteins with distinguishable sizes and properties. The roles in induction of the flavone (luteolin) inducer, the regulatory upstream DNA sequences, the NodD protein, and RNA polymerase will be studied. Luteolin will be labelled and its receptor protein identified. NodD and NodD3 will be purified and characterized to determine the basis for NodD mediating flavone induction of nod genes, while NodD3 causes constitutive nod gene expression. RNA polymerase will be purified, and specialized sigma factors will be isolated and characterized for effects on nod gene expression. Deletion analysis will be used to indicate the roles of sequences upstream of inducible nod genes. The existence of regulatory genes besides nodD will be tested genetically, and the products of such genes will be characterized. The specific hypothesis that NodD binds flavone, and activates transcription through direct interaction with DNA, will be analyzed in detail.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM030962-11
Application #
3278860
Study Section
Microbial Physiology and Genetics Subcommittee 2 (MBC)
Project Start
1982-07-01
Project End
1993-07-31
Budget Start
1992-08-01
Budget End
1993-07-31
Support Year
11
Fiscal Year
1992
Total Cost
Indirect Cost
Name
Stanford University
Department
Type
Schools of Arts and Sciences
DUNS #
800771545
City
Stanford
State
CA
Country
United States
Zip Code
94305
Peck, Melicent C; Fisher, Robert F; Bliss, Robert et al. (2013) Isolation and characterization of mutant Sinorhizobium meliloti NodD1 proteins with altered responses to luteolin. J Bacteriol 195:3714-23
Krol, Elizaveta; Blom, Jochen; Winnebald, Jorn et al. (2011) RhizoRegNet--a database of rhizobial transcription factors and regulatory networks. J Biotechnol 155:127-34
Becker, Anke; Barnett, Melanie J; Capela, Delphine et al. (2009) A portal for rhizobial genomes: RhizoGATE integrates a Sinorhizobium meliloti genome annotation update with postgenome data. J Biotechnol 140:45-50
Margolin, W; Bramhill, D; Long, S R (1995) The dnaA gene of Rhizobium meliloti lies within an unusual gene arrangement. J Bacteriol 177:2892-900
Margolin, W; Long, S R (1993) Isolation and characterization of a DNA replication origin from the 1,700-kilobase-pair symbiotic megaplasmid pSym-b of Rhizobium meliloti. J Bacteriol 175:6553-61
Long, S R; Staskawicz, B J (1993) Prokaryotic plant parasites. Cell 73:921-35
Rushing, B G; Yelton, M M; Long, S R (1991) Genetic and physical analysis of the nodD3 region of Rhizobium meliloti. Nucleic Acids Res 19:921-7
Barnett, M J; Long, S R (1990) DNA sequence and translational product of a new nodulation-regulatory locus: syrM has sequence similarity to NodD proteins. J Bacteriol 172:3695-700
Fisher, R F; Long, S R (1989) DNA footprint analysis of the transcriptional activator proteins NodD1 and NodD3 on inducible nod gene promoters. J Bacteriol 171:5492-502
Long, S R (1989) Rhizobium-legume nodulation: life together in the underground. Cell 56:203-14

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