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A Rhizobium meliloti DNA region (nodD1) involved in the regulation of other early nodulation genes has been delimited by directed Tn5 mutagenesis and its nucleotide sequence has been determined. The sequence data indicate a large open reading frame with opposite polarity to nodA, -B and -C, coding for a protein of 308 (or 311) amino acid residues. Tn5 insertion within the gene caused a delay in nodulation of Medicago sativa from four to seven days. Hybridization of nodD1 to total DNA of Rhizobium meliloti revealed two additional nodD sequences (nodD2 and nodD3) and both were localized on the megaplasmid pRme41b in the vicinity of the other nod genes. Genetic and DNA hybridization data, combined with nucleotide sequencing showed that nodD2 is a functional gene, while requirement of nodD3 for efficient nodulation of M. sativa could not be detected under our experimental conditions. The nodD2 gene product consists of 310 amino acid residues and shares 86.4% homology with the nodD1 protein. Single nodD2 mutants had the same nodulation phenotype as the nodD1 mutants, while a double nodD1-nodD2 mutant exhibited a more severe delay in nodulation. These results indicate that at least two functional copies of the regulatory gene nodD are necessary for the optimal expression of nodulation genes in R. meliloti.
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B Horvath, and
E Kondorosi, and
P Putnoky, and
F Rodriguez-Quiñones, and
A Kondorosi
September 1981,
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M Göttfert, and
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A Kondorosi
February 1988,
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M Göttfert, and
B Horvath, and
E Kondorosi, and
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F Rodriguez-Quiñones, and
A Kondorosi
June 1985,
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M Göttfert, and
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A Kondorosi
August 1986,
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M Göttfert, and
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A Kondorosi
December 1984,
Nucleic acids research,
M Göttfert, and
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A Kondorosi
February 1988,
Molecular plant-microbe interactions : MPMI,
M Göttfert, and
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June 1985,
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M Göttfert, and
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A Kondorosi
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M Göttfert, and
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E Kondorosi, and
P Putnoky, and
F Rodriguez-Quiñones, and
A Kondorosi
February 1990,
Journal of bacteriology,
M Göttfert, and
B Horvath, and
E Kondorosi, and
P Putnoky, and
F Rodriguez-Quiñones, and
A Kondorosi
May 1987,
The Journal of biological chemistry,
