Localization of functional regions of the Rhizobium nodD product using hybrid nodD genes

The flavonoid-inducible nod promoters of Rhizobium are positively regulated by the nodD gene which is highly conserved in various Rhizobium species. The nodD gene are functionally different in (i) their response to various exogenously added flavonoid inducers, (ii) the extent to which they mediate the activation of the flavonoid-inducible promoters, and (iii) the extent to which they repress their own constitutive transcription. In order to localize the regions of the nodD product which determine these differences, two series of nodD hybrid genes have been constructed. In one series the 5′ moiety is derived from the R. meliloti nodD1 gene and the 3′ moiety from the R. trifolii nodD gene. In the other series, the origins of the nodD moieties are reversed. Two regions of the nodD product appeared to be involved in autoregulation and it was also shown that the nodD promoters differ in their susceptibility to autoregulation. Many regions, dispersed over the entire nodD product, are involved in the specificity of activation by flavonoids. Several hybrid nodD genes were characterized which activate transcription with novel inducers. Furthermore, two classes of hybrid nodD genes were found from which the activation characteristics differ completely from those of the parental nodD genes. The first class activates the nodABCIJ promoter to the maximum level in the absence of flavonoid inducer. This level can no longer be influenced, positively or negatively, by the presence of (iso-)flavonoids. With the second class of hybrids, activation of the nodABCIJ promoter, even in the presence of flavonoid inducers, is no longer possibleMicrobial Biotechnolog

Detection and subcellular localization of two Sym plasmid-dependent proteins of Rhizobium leguminosarum biovar viciae

Microbial Biotechnolog

Isolation and characterization of ropA homologous genes from Rhizobium leguminosarum biovars viciae and trifolii

Microbial Biotechnolog

A Rhizobium leguminosarum Biovar trifolii locus not localized on the sym plasmid hinders effective nodulation on plants of the pea cross-inoculation group

Microbial Biotechnolog

Amino acid synthesis is necessary for tomato root colonization by Pseudomonas fluorescens strain WCS365

Microbial Biotechnolog

Bacteriocin small of Fast-growing rhizobia is chloroform soluble and is not required for effective nodulation

Microbial Biotechnolog

Construction of phoE-caa, a novel PCR- and Immunologically detectable marker gene for pseudomonas putida

Microbial Biotechnolog

A two-component system plays an important role in the root-colonizing ability of Pseudomonas fluorescens strain WCS365

Microbial Biotechnolog

Distribution of O-acetyl groups in the exopolysaccharide synthesized by Rhizobium leguminosarum strains is not determined by the sym plasmid

Microbial Biotechnolog

Induction of the nodA promoter Rhizobium leguminosarum Sym plasmid pRL1JI by plant flavanones and flavones

An expression vector containing the Rhizobium leguminosarum nodA promoter cloned in front of the Escherichia coli lacZ gene was used to characterize the properties of the R. leguminosarum nodA gene-inducing compound(s) present in sterile root exudate of the host plant Vicia sativa L. subsp. nigra (L.). The major inducing compound was flavonoid in nature, most likely a flavanone. The commercially available flavonoids naringenin (5,7,4'-trihydroxyflavanone), eriodictyol (5,7,3'4'-tetrahydroxyflavanone), apigenin (5,7,4'-trihydroxyflavone), and luteolin (5,7,3',4'-tetrahydroxyflavone) induced the nodA promoter to the same level as the root exudate. On the basis of chromatographic properties, it was concluded that none of these compounds is identical to the inducer that is present in root exudate. The induction of the nodA promoter by root exudate and by the most effective inducer naringenin was very similar, as judged from the genetic requirements and the kinetics of induction.Plant sciencesBio-organic SynthesisMicrobial Biotechnolog