Impaired nitrogen fixation and glutamine synthesis in methionine sulfoximine sensitive (MSs) mutants of Rhizobium phaseoli

Morett, Enrique; Moreno, Soledad; Espı́n, Guadalupe

doi:10.1007/bf00425428

Cited by 15 publications

(3 citation statements)

References 35 publications

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“…Interestingly, in that strain of R. phaseoli symbiotic mutations have been mapped to the chromosome and to three different plasmids (32). In a different R. phaseoli strain, a gene (psi) which inhibits exopolysaccharide production and is required for symbiotic nitrogen fixation has been described (7).…”

Section: Discussionmentioning

confidence: 99%

Second symbiotic megaplasmid in Rhizobium meliloti carrying exopolysaccharide and thiamine synthesis genes

Finan¹,

Kunkel²,

Vos³

et al. 1986

J Bacteriol

574

362

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Using physical and genetic data, we have demonstrated that Rhizobium meliloti SU47 has a symbiotic megaplasmid, pRmeSU47b, in addition to the previously described nod-nif megaplasmid pRmeSU47a. This plasm'id includes four loci involved in exopolysaccharide (exo) synthesis as well as two loci involved in thiamine 1'iosynthesis. Mutations at the exo loci have previously been shown to result in the formation of nodules which lack infection threads (Inf)' and fail to fix nitrogen (Fix-). Thus, both megaplasmids contain genes involved in the formation of nitrogen-fixing root nodules. Mutations at two other exo loci were not located on either megaplasmid. To mobilize the megaplasmids, the oriT of plasmid RK2 was inserted into them. On alfalfa, Agrobacterium tumefaciens strains containing pRmeSU47a induced marked root hair curling with no infection threads and Fix-nodules, as reported by others. This plant phenotype was not observed to change with A. tumefaciens strains containing both pRmeSU47a and pRmeSU47b megaplasmids, and strains containing pRmeSU47b alone failed to curl root hairs or form nodules.A great many natural isolates of rhizobia, agrobacteria, and pseudomonads have been shown to carry a variety of large plasmids (for examples, see references 8, 21, and 38). Some of these are megaplasmids, with molecular masses over 450 megadaltons (38). Genes for a few functions have been localized to these large plasmids, notably including pathogenicity gepes for the Ti and Ri plasmids of agrobacteria (6, 21) and symbiotic nodulation (nod) and nitrogen fixation (nif) genes for the Sym megaplasmids of the fast-growing rhizobia (3,8,28,33,37,38). Nevertheless, the significance of this genomic organization remains obscure, although the fact that these are all plant-associated soil bacteria does suggest an underlying evolutionary cause.Rhizobial Sym megaplasmids are being characterized extensively with regard to symbiosis. In addition, Rhizobium meliloti 41 has recently been shown to carry a second megaplasmid, with a molecular weight very nearly that of pSym, on which a region for surface exclusion (although none for symbiotic functions) has tentatively been identified (2). A second megaplasmid has also been identified in R.

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Section: Discussionmentioning

confidence: 99%

Second symbiotic megaplasmid in Rhizobium meliloti carrying exopolysaccharide and thiamine synthesis genes

Finan¹,

Kunkel²,

Vos³

et al. 1986

J Bacteriol

574

362

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“…Mutants of R . Ieguminosarum biovarphaseoli lacking GSII are Nod+ and Fix+ (Morett et al, 1985). Mutants of B. japonicum lacking either GSI or GSII are Gln+, Nod+ and Fix+; double mutants are Gln-and Nod- (Carlson et al, 1987).…”

Section: Introductionmentioning

confidence: 99%

Regulation of Glutamine Synthetase Isoenzymes in Rhizobium leguminosarum biovar viceae

Rossi¹,

Defez²,

Chiurazzi³

et al. 1989

Microbiology

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Ammonia assimilation in Rhizobium leguminosarum biovar viceae strain RCRlOO 1 (hereafter called R . leguminosarum) appears to take place only through the glutamine synthetase/glutamate synthase pathway since (a) no glutamate dehydrogenase was detected in crude extracts of bacteria grown in different nitrogen sources, and (b) the growth rate on glutamine as a nitrogen source was faster than that observed on NH4Cl. In contrast to reports for other Rhizobium species, R . leguminosarum can definitely utilize NH4C1 for growth. R. Ieguminosarum contains two glutamine synthetase isoenzymes, GSI and GSII, which can be detected in the presence of each other by differential heat stability, or separated by affinity chromatography or immunoabsorption with an antiserum raised against pure GSI. GSII does not cross-react with an anti-GSI antiserum. GSI was shown to be reversibly adenylylated and it was also shown that adenylylation inhibits the biosynthetic activity of this enzyme, in a similar way to that reported for Escherichia coli glutamine synthetase and in contrast to that observed for glutamine synthetase of Rhizobium sp. strain ANU289. The apparent adenylylation level in different growth conditions changes from 21% to 99%, indicating a physiological role of this posttranslational modification in the in vivo regulation of GSI activity. The intracellular concentration of GSI varies very little when R . leguminosarum is grown on different nitrogen sources (twofold when measured by the transferase assay, or fourfold when measured by ELISA). In addition, the concentration of mRNA specific for GSI in different nitrogen sources does not show appreciable differences. The intracellular concentration of GSII varies from a specific activity value higher than 1000 when R . leguminosarum is grown on glutamate or nitrate, to an undetectable level when grown on NH4C1. When NH4C1 is added to a culture growing in glutamate, GSII activity is rapidly diluted out, suggesting a post-translational mechanism of enzyme inhibition or inactivation. Chloramphenicol prevents the disappearance of GSII activity, thus suggesting that protein synthesis is required for this process.

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“…LUDWIG (12,13), MORETT et al (14), and de BRUIJN et al (1) have isolated strains of Rhizobium and Bradyrhizobium which were GSI + GSII -illustrating that GSI alone is fully competent to supply the cell with glutamine. The competency of GSII to supply the cell with glutamine in B, japonicum 61A76 was supported by studies on the steady state kinetics of GSI and GSII (R. A. DARROW and R. R. KNOTTS, Abstracts of the 8th North American Rhizobium Conference, Univ.…”

mentioning

confidence: 99%

Characteristics of glutamine synthetase I and II mutants of Rhizobium.

Keister

Jones

Kondorosi

et al. 1987

J. Gen. Appl. Microbiol.

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MutantsCharacteristic isoenzymes of glutamine synthetase (GS) are found in the Rhizobiaceae which includes Agrobacterium, 12,13). GSI has many properties similar to the GS found in enteric bacteria (3) while GSII appears solely in the Rhizobiaceae (7) and has properties distinctly different from GSI (3,4). LUDWIG (12, 13), MORETT et al. (14), and de BRUIJN et al. (1) have isolated strains of Rhizobium and Bradyrhizobium which were GSI + GSII -illustrating that GSI alone is fully competent to supply the cell with glutamine. The competency of GSII to supply the cell with glutamine in B,

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Impaired nitrogen fixation and glutamine synthesis in methionine sulfoximine sensitive (MSs) mutants of Rhizobium phaseoli

Cited by 15 publications

References 35 publications

Second symbiotic megaplasmid in Rhizobium meliloti carrying exopolysaccharide and thiamine synthesis genes

Second symbiotic megaplasmid in Rhizobium meliloti carrying exopolysaccharide and thiamine synthesis genes

Regulation of Glutamine Synthetase Isoenzymes in Rhizobium leguminosarum biovar viceae

Characteristics of glutamine synthetase I and II mutants of Rhizobium.

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