Sequence analysis of the Azospirillum brasilense exoB gene, encoding UDP-glucose 4'-epimerase

Troch, Paul De; Keijers, Veerle; Vanderleyden, Jozef

doi:10.1016/0378-1119(94)90221-6

Cited by 19 publications

(17 citation statements)

References 15 publications

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“…The sequence of B5 was also similar to a plasmid-encoded glycosyl transferase of A. brasilense (Vanbleu et al 2004), suggesting it to be a homolog. In fact, several genes encoding putative glycosyl transferases in A. brasilense are located on the p90 plasmid, which is thought to play a major role in determining the composition of the cell envelope, forming the primary defense of the bacterium against stress conditions and antimicrobial molecules (Vanbleu et al 2004;De Troch et al 1994).…”

Section: Resultsmentioning

confidence: 99%

Identification of salt stress inducible genes that control cell envelope related functions in Azospirillum brasilense Sp7

2007

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Plant growth promoting rhizobacteria such as Azospirillum brasilense are agronomically important as they are frequently used for crop inoculation. But adverse factors such as increasing soil salinity limit their survival, multiplication and phytostimulatory effect. In order to understand the role of the genes involved in the adaptation of A. brasilense Sp7 to salt stress, a mutant library (6,800 mutants) was constructed after random integration of a mini-Transposon Tn5 derivative containing a promoterless gusA and oriV. The library was screened for salt stress inducible Gus activity on minimal malate agar medium containing NaCl and 5-bromo-4-chloro-3-indolyl-beta-D: -glucuronide. Salt stress responsiveness of the promoters was estimated by quantifying GusA activity in the presence and absence of NaCl stress using p-nitrophenyl-beta-D: -glucuronide as a substrate. In 11 mutants showing high levels of gusA expression in the presence of salt-stress, the partial nucleotide sequence of the DNA region flanking the site of Tn5 insertion was determined and analysed using the NCBI-BLAST programs. Similarity searches revealed that 10 out of the 11 genes sequenced showed notable similarity with genes involved in functions related to modulation in the composition of exopolysaccharides, capsular polysaccharides, lipopolysaccharides, peptidoglycan and lipid bilayer of the cell envelope. Induction of cell envelope related genes in response to salt stress and salt sensitive phenotype of several mutants in A. brasilense indicate a prominent role of cell envelope in salt-stress adaptation.

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Section: Resultsmentioning

confidence: 99%

Identification of salt stress inducible genes that control cell envelope related functions in Azospirillum brasilense Sp7

2007

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“…G. metallireducens also has a putative fructose 6-kinase (Gmet_2805, 39% identical to the E. coli enzyme [76]) that is not present in G. sulfurreducens . Remarkably, G. metallireducens possesses two isoenzymes each of UDP-glucose 4-epimerase (Gmet_1486; Gmet_2329 = GSU2240, 50% and 54% identical to the A. brasilense enzyme [77]), glutamine:fructose-6-phosphate aminotransferase (Gmet_1487; Gmet_0104 = GSU0270, 55% and 53% identical to the Thermus thermophilus enzyme [78]), GDP-mannose 4,6-dehydratase (Gmet_1488 = GSU0626; Gmet_1311, 61% and 72% identical to the E. coli enzyme [79]) and UDP- N -acetylglucosamine 2-epimerase (Gmet_1489 = GSU2243, 61% identical to the E. coli enzyme [80]; Gmet_1504, 39% identical to the Methanococcus maripaludis enzyme [81]). G. metallireducens has evolved a gene cluster of the four enzyme activities (Gmet_1486-Gmet_1489) from both ancestral gene duplication and lateral gene transfer (data not shown).…”

Section: Resultsmentioning

confidence: 99%

The genome sequence of Geobacter metallireducens: features of metabolism, physiology and regulation common and dissimilar to Geobacter sulfurreducens

et al. 2009

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BackgroundThe genome sequence of Geobacter metallireducens is the second to be completed from the metal-respiring genus Geobacter, and is compared in this report to that of Geobacter sulfurreducens in order to understand their metabolic, physiological and regulatory similarities and differences.ResultsThe experimentally observed greater metabolic versatility of G. metallireducens versus G. sulfurreducens is borne out by the presence of more numerous genes for metabolism of organic acids including acetate, propionate, and pyruvate. Although G. metallireducens lacks a dicarboxylic acid transporter, it has acquired a second putative succinate dehydrogenase/fumarate reductase complex, suggesting that respiration of fumarate was important until recently in its evolutionary history. Vestiges of the molybdate (ModE) regulon of G. sulfurreducens can be detected in G. metallireducens, which has lost the global regulatory protein ModE but retained some putative ModE-binding sites and multiplied certain genes of molybdenum cofactor biosynthesis. Several enzymes of amino acid metabolism are of different origin in the two species, but significant patterns of gene organization are conserved. Whereas most Geobacteraceae are predicted to obtain biosynthetic reducing equivalents from electron transfer pathways via a ferredoxin oxidoreductase, G. metallireducens can derive them from the oxidative pentose phosphate pathway. In addition to the evidence of greater metabolic versatility, the G. metallireducens genome is also remarkable for the abundance of multicopy nucleotide sequences found in intergenic regions and even within genes.ConclusionThe genomic evidence suggests that metabolism, physiology and regulation of gene expression in G. metallireducens may be dramatically different from other Geobacteraceae.

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“…The exoB gene coded for a predicted protein that showed 80.0% identity and 89.2% similarity to the deduced amino acid sequence of the UDP-glucose 4-epimerase of R. meliloti. The exoB gene of R. leguminosarum bv trifolii also showed signi®cant homology to gene sequences coding for UDP-glucose 4-epimerase in Azospirillum brasilense (49.5% identity, 64.3% similarity) (De Troch et al 1994) and E. coli (41.7% identity, 58.5% similarity) (Lemaire and MuÈ ller-Hill 1986). …”

Section: Resultsmentioning

confidence: 99%

Structure and role in symbiosis of the exoB gene of Rhizobium leguminosarum bv trifolii

et al. 1997

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The Rhizobium leguminosarum bv trifolii exoB gene has been isolated by heterologous complementation of an exoB mutant of R. meliloti. We have cloned a chromosomal DNA fragment from the R. leguminosarum bv trifolii genome that contains an open reading frame of 981 bp showing 80% identity at the amino acid level to the UDP-glucose 4-epimerase of R. meliloti. This enzyme produces UDP-galactose, the donor of galactosyl residues for the lipid-linked oligosaccharide repeat units of various heteropolysaccharides of rhizobia. An R. leguminosarum bv trifolii exoB disruption mutant differed from the wild type in the structure of both the acidic exopolysaccharide and the lipopolysaccharide. The acidic exopolysaccharide made by our wild-type strain is similar to the Type 2 exopolysaccharide made by other R. leguminosarum bv trifolii wild types. The exopolysaccharide made by the exoB mutant lacked the galactose residue and the substitutions attached to it. The exoB mutant induced the development of abnormal root nodules and was almost completely unable to invade plant cells. Our results stress the importance of exoB in the Rhizobium-plant interaction.

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Sequence analysis of the Azospirillum brasilense exoB gene, encoding UDP-glucose 4'-epimerase

Cited by 19 publications

References 15 publications

Identification of salt stress inducible genes that control cell envelope related functions in Azospirillum brasilense Sp7

Identification of salt stress inducible genes that control cell envelope related functions in Azospirillum brasilense Sp7

The genome sequence of Geobacter metallireducens: features of metabolism, physiology and regulation common and dissimilar to Geobacter sulfurreducens

Structure and role in symbiosis of the exoB gene of Rhizobium leguminosarum bv trifolii

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