Sequence and analysis of the rpoN sigma factor gene of rhizobium sp. strain NGR234, a primary coregulator of symbiosis.
We report the nucleotide sequence of the rpoN gene from broad-host-range Rhizobium sp. strain NGR234 and analyze the encoded RPON protein, a sigma factor. Comparative analysis of the deduced amino acid sequence of RPON from NGR234 with sequences from other gram-negative bacteria identified a perfectly conserved RPON box unique to RPON sigma factors. Symbiotic regulatory phenotypes were defined for a site-directed internal deletion within the coding sequence of the rpoN gene of Rhizobium strain NGR234: they included quantitative nodulation kinetics on Vigna unguiculata and microscopic analysis of the Fix- determinate nodules of V. unguiculata and Macroptilium atropurpureum. RPON was a primary coregulator of nodulation and was implicated in establishment or maintenance of the plant-synthesized peribacteroid membrane. Phenotypes of rpoN in Rhizobium strain NGR234 could be grouped as symbiosis related, rather than simply pleiotropically physiological as in free-living bacteria such as Klebsiella pneumoniae and Pseudomonas putida.
Laboratoire de Biologie Moleculaire des Plantes Superieures, University of Geneva, Chambésy, Switzerland.
J C
JC
van Slooten
E
E
Cervantes
W J
WJ
Broughton
C H
CH
Wong
J
J
Stanley
D000595:Amino Acid Sequence; D001483:Base Sequence; D002872:Chromosome Deletion; D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics; D007887:Fabaceae / Q000502:physiology; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D010641:Phenotype; D010944:Plants / Q000648:ultrastructure; D010946:Plants, Medicinal; D010957:Plasmids; D015183:Restriction Mapping; D012231:Rhizobium / Q000235:genetics* / Q000502:physiology / Q000648:ultrastructure; D012689:Sequence Homology, Nucleic Acid; D012808:Sigma Factor / Q000235:genetics*; D013559:Symbiosis
D004269:DNA, Bacterial; D012808:Sigma Factor