The Lubrizol Corporation

Lubrizol Genetics, Inc.

Mycogen Plant Science, Inc.

Barry G Rolfe

Kieran F Scott

John Shine

Hauke Hennecke

John M Watson

Michael A Djordjevic

Peter R Schofield

Peter Schofield

John W Redmond

Michael Batley

Roger W Innes

Peter L Kuempel

The invention includes a consensus nucleotide sequence found in the promoter regions of those Rhizobium and Bradyrhizobium nodulation genes which are activated by chemical inducer(s) in legume exudate. A promoter comprising the consensus sequence is a legume exudate-inducible promoter. A recombinant gene comprising a structural gene and a legume exudate-inducible promoter is selectively expressed in the presence of legume exudate or chemical inducer(s) and a functional nodD gene. The consensus nucleotide sequence is ATCCAYNNYGYRGATGNWYKYKATCSAAWCAATCRATTTTACCARWYYKNSRR where

Nodulation gene promoter

Nodulation gene-inducing factors have been isolated and identified. A number of substituted flavones, some of which are components of exudates and extracts of leguminous plants, have been found to induce expression of certain nodulation genes in Rhizobium strains. Three components of clover extract 7,4'-dihydroxyflavone, 7,4'-dihydroxy-3'methoxyflavone, and 4'-hydroxy-7-methoxyflavone have been identified as nodulation inducers of certain Rhizobium trifolii nod genes. A number of other flavonoids including flavones, flavanones, flavanols and dihydroflavanols, not necessarily found in legume exudates, were also found to induce expression of certain nodulation genes.

Nodulation inducing factors

This invention provides useful promoters from the R. trifolii nifH gene for the construction of recombinant molecules to regulate foreign genes for expression under desired conditions. In particular, the promoters act to control expression of the foreign genes within root nodules formed by rhizobial bacterial strains in symbiotic combination with host plants. A rhizobium diagnostic segment (RDS) is also provided comprising a DNA segment found at more than one location in rhizobia, the RDS being species-specific, and detectable by DNA hybridization under stringent conditions. A recombinant plasmid comprising a RDS and a bacterial strain containing the plasmid are provided. Methods are provided for identifying species and strains of field isolates of Rhizobium, using RDS's. One RDS exemplified comprises 5' sequences from the R. trifolii nifH gene.

Rhizobial diagnostic probes and rhizobium trifolii nifH promoters

The nifH promoter regions of Bradyrhizobium japonicum and Bradyrhizobium sp. (parasponia) have been sequenced and found to be significantly homologous. Recombinant DNA molecules comprising foreign genes under the control of such promoters are provided. Rhizobial species containing such recombinant constructions, either in plasmids or integrated into the genome, are provided. These are especially useful for expressing desired foreign genes within root nodules.

nifH promoters of Bradyrhizobium

The nifD promoter regions of Bradyrhizobium japonicum and Bradyhizobium sp. (Parasponia) have been sequenced and found to be significantly homologous. Recombinant DNA molecules comprising foreign genes under the control of such promoters are provided. Rhizobial species containing such recombinant constructions, either in plasmids or integrated into the genome, are provided. These are especially useful for expressing desired foreign genes within root nodules.

nifD promoter of Bradyrhizobium

Growing community of inventors

Curtin, Australia

Barry G Rolfe