Isolation and Characterization of a<i>Rhizobium loti</i>Gene Required for Effective Nodulation of<i>Lotus pedunculatus</i>

Ward, Lawrence J. H.; Rockman, E. S.; Ball, Peter; Jarvis, B. D. W.; Scott, David B.

doi:10.1094/mpmi-2-224

Cited by 15 publications

(8 citation statements)

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“…In R. meliloti, Rhizobium leguminosarum bv. viciae, and B. japonicum, C4-dicarboxylate transport mutants formed ineffective (Fix-) nodules (6,30,41) that have been reported, nitrogen fixation ability is significantly reduced compared with that of the wild type but not completely blocked (11,15,29,52,60,62). These results suggest that the host-specific failure is due to some postinfection breakdown in the interaction between plant and bacterium and is not directly related to the nitrogen fixation enzymatic machinery.…”

Section: Resultsmentioning

confidence: 49%

“…Indeed, nucleotide sequence information is available for only one gene of R loti NZP2037 required for effective nodulation of L. pedunculatus but not for L. comiculatus (60). However, there exists no significant similarity between the hsfA gene sequence reported here and the R loti gene.…”

Section: Resultsmentioning

confidence: 77%

“…For this reason, we chose to name ORFA hsfA (for host-specific fixation). DISCUSSION Host-specific fixation mutants of several Rhizobium and Bradyrhizobium strains have been reported (10,29,52,60,62). However, these earlier reports failed to identify the specific gene(s) responsible for the host-specific fixation phenotype.…”

Section: Resultsmentioning

confidence: 99%

“…Mutants of rhizobia which have lost the ability to fix nitrogen with some, but not all, of their normal legume hosts have been isolated (10,14,29,52,60,62). Tn5-induced mutants of Rhizobium strain NGR234" with altered exopolysaccharide production produce Fix' nodules on some of their hosts but t Present address: Department of Nutritional Science, University of California-Berkeley, Berkeley, CA 94720.…”

mentioning

confidence: 99%

“…Nucleotide sequence information is available for only one gene from R loti NZP2037 required for effective nodulation of L. pedunculatus but not for Lotus comiculatus (60). Thus, very little is known about the molecular aspects of host-specific nitrogen fixation in legumes.…”

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confidence: 99%

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Identification and characterization of a novel Bradyrhizobium japonicum gene involved in host-specific nitrogen fixation

et al. 1994

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To understand the genetic mechanism of host specificity in the interaction between rhizobia and their hosts, it is important to identify genes that influence both early and late steps in symbiotic development. This paper focuses on the little-understood genetics of host-specific nitrogen fixation. A deletion mutant ofBradyrhizobium japonicum, strain NAD163, was found to induce effective, nitrogen-fixing nodules on soybean and siratro plants but produced ineffective nodules on cowpea plants. Additional transposon and deletion mutants defined a small region that conferred this phenotype, and this region was sequenced to identify two putative open reading frames (ORFs). Data indicate that only one of these ORFs is detectable in bacteroids. This ORF was termed hsfA, with a predicted protein product of 11 kDa. The transcriptional start site of hsfA was determined and found to coincide with a predicted RpoN-dependent promoter. Microscopic studies of nodules induced by the wild type and hsfA mutants on cowpea and soybean plants indicate that the cowpea mutant nodules are slow to develop. The data indicate that hsfA appears to play a crucial role in bacteroid development on cowpea but does not appear to be essential for nitrogen fixation on the other hosts tested.It is well-known that specific strains of rhizobia enter into nitrogen-fixing symbioses with specific hosts. A number of host-specific genetic determinants that affect the early steps of symbiosis, infection, and nodulation (e.g., root hair curling and cortical cell division; see references 3, 21, and 31) have been studied. However, less is known about host-specific events that affect later steps in the development and maintenance of the symbiosis.Bacterial host specificity in symbiotic nitrogen fixation has been suggested by the observation that some wild-type Rhizobium strains form effective (Nod' Fix') nodules on some legumes but form ineffective (Nod' Fix-) nodules on other hosts (e.g., see references 9, 16, 37, and 55

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