Cloning of the symbiotic region of Rhizobium leguminosarum: the nodulation genes are between the nitrogenase genes and a nifA-like gene.
The region of the Rhizobium leguminosarum plasmid pRL1JI involved in nodulation and nitrogen fixation has been cloned on a series of four overlapping cosmid clones. These clones represent 60 kb of pRL1JI DNA on which a series of Tn5-induced fix and nod alleles have been identified, with the two most distant alleles being separated by 45 kb of DNA. The mutant alleles fell into three groups, two clusters of fix alleles separated by one cluster of nod alleles. Within one group of fix alleles, DNA homologous to the nifA gene of Klebsiella pneumoniae has been identified, whereas the pRL1JI DNA homologous to the K. pneumoniae nitrogenase genes is present within the other group of fix alleles.
Downie
J A
JA
John Innes Institute, Colney Lane, Norwich NR4 7UH, UK.
Ma
Q S
QS
Knight
C D
CD
Hombrecher
G
G
Johnston
A W
AW