Role of the<i>fixGHI</i>region of<i>Azorhizobium caulinodans</i>in free-living and symbiotic nitrogen fixation

Mandon, Karine; Kaminski, P.A.; Mougel, Christophe; Desnoues, Nicole; Dreyfus, B; Elmerich, Claudine

doi:10.1111/j.1574-6968.1993.tb06571.x

Cited by 21 publications

(8 citation statements)

References 9 publications

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“…5). In addition, the 558 (30). The cloned region is adjacent to fixGHI and is not linked to the fixLJK genes, and thus the organization is unlike that in R. meliloti and B. japonicum (30).…”

Section: Resultsmentioning

confidence: 99%

“…In addition, the 558 (30). The cloned region is adjacent to fixGHI and is not linked to the fixLJK genes, and thus the organization is unlike that in R. meliloti and B. japonicum (30). The nucleotide sequence of a 4-kb fragment contains four ORFs which were assigned to fixNOQP and the beginning of a fifth ORF namedfixG on the basis of their similarity with the corresponding genes of R. meliloti and B. japonicum (6,19,36).…”

Section: Resultsmentioning

confidence: 99%

“…A 19-kb DNA fragment of the A. caulinodans genome which exhibited similarity to the fixNOQP and fixGHI operons of R. meliloti was cloned previously (30). The region similar to fixN was localized in a 6-kb BglII fragment, which was subcloned into pSUP202 to yield pRS3010 (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…(A preliminary account of the characterization of the fixNOQP genes was reported at the 9th International Congress on Nitrogen Fixation, Cancun, Mexico [29]. )…”

mentioning

confidence: 99%

“…The cloning of the fixNOQP-fixGHI region of A. caulinodans and the characterization of fixGHI insertional Tn5 mutants have been reported elsewhere (30).…”

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confidence: 99%

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Functional analysis of the fixNOQP region of Azorhizobium caulinodans

1994

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The deduced amino acid sequences of four open reading frames identified upstream of thefixGHI region in Azorhizobium caulinodans are very similar to the putative terminal oxidase complex coded by the fixNOQP operons from Rhizobium meliloti and Bradyrhizobium japonicum. The expression of the A. caulinodansfixNOQP genes, which was maximal under microaerobiosis, was positively regulated by FixK and independent of NifA. In contrast to the Fix-phenotype of B.japonicum and R. melilotifixN mutants, anA. caulinodansfixNO-deleted mutant strain retained 50%o of the nitrogenase activity of the wild type in the symbiotic state. In addition, the nitrogenase activity was scarcely reduced under free-living conditions. Analysis of membrane fractions of A.caulinodans wild-type and mutant strains suggests that the fixNOQP region encodes two proteins with covalently bound hemes, tentatively assigned tofixO andfixP. Spectral analysis showed a large decrease in the c-type cytochrome content of thefixN mutant compared with the wild type. These results provide evidence for the involvement of FixNOQP proteins in a respiratory process. The partial impairment in nitrogen fixation of thefixN mutant in planta may be due to the activity of an alternative terminal oxidase compensating for the loss of the oxidase complex encoded byfixNOQP.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

“…(A preliminary account of the characterization of the fixNOQP genes was reported at the 9th International Congress on Nitrogen Fixation, Cancun, Mexico [29]. )…”

mentioning

confidence: 99%

“…The cloning of the fixNOQP-fixGHI region of A. caulinodans and the characterization of fixGHI insertional Tn5 mutants have been reported elsewhere (30).…”

mentioning

confidence: 99%

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