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PubMed1989

The consensus sequence of ice nucleation proteins from Erwinia herbicola, Pseudomonas fluorescens and Pseudomonas syringae.

The consensus sequence of three bacterial ice nucleation proteins was determined by extrapolation from the nucleotide (nt) sequences of three ice nucleation-encoding genes, iceE (presented here), inaW and inaZ. The three proteins possess considerable similarity, so that a preferred amino acid is shown in most positions of the consensus. The corresponding genes show considerable divergence in the third nt positions of synonymous codons, suggesting that the proteins' conserved features have been maintained by selection. Therefore, the consensus sequence is likely to represent the components of primary structure most important to the ice nucleation function.

Amino Acid Sequence↗
PubMed1997

Biological activities of pseudomycin A, a lipodepsinonapeptide from Pseudomonas syringae MSU 16H.

Similarly to other Pseudomonas lipodepsinonapeptides, pseudomycin A inhibits proton extrusion from maize roots, promotes closure of stomata in Vicia faba, necrosis of tobacco leaves, haemolysis of human erythrocytes, affects H(+)-ATPase activity and proton translocation in plasma membrane vesicles, and stimulates succinate respiration in pea mitochondria. In general, the biological activities of pseudomycin A are lower than those of syringomycin-E, the prototype member of this family of bacterial metabolities. This difference might depend on the diverse number and distribution of charged residues in the peptide moiety of these compounds.

Amino Acid Sequence↗
PubMed1984

Purification and some properties of the D-lactate-2-sulphatase of Pseudomonas syringae GG.

A soil bacterium grown on propan-2-yl sulphate as sole source of carbon and sulphur yielded extracts containing an enzyme capable of liberating sulphate from racemic lactate-2-sulphate. The enzyme was purified to homogeneity by a combination of streptomycin sulphate precipitation of nucleic acids, batch treatment with DEAE-cellulose, and chromatography on columns of DEAE-cellulose, Sephacryl S-300 and butyl-agarose. The protein was monomeric with an Mr of 55 000-60 000. The enzyme activity was specific for D-lactate-2-sulphate (Km 6.6 nM; maximal specific activity 14.3 mumol/min per mg of protein) and showed no activity towards the L-isomer. The products of the enzyme's action were inorganic sulphate and D-lactate which were released in equimolar amounts and stoicheiometrically with the amount of ester hydrolysed. No L-lactate was formed. Retention of configuration implied cleavage of the O-S bond of the C-O-S ester link and this was confirmed by 18O-incorporation experiments in which 18O from 18O-enriched water in the incubation medium was incorporated exclusively and quantitatively into inorganic sulphate. Only two other esters (serine-O-sulphate and p-nitrophenyl sulphate) of a total of 29 compounds tested were substrates for the enzyme. D-Lactate, L-lactate-2-sulphate and the substrate analogues glycollate-2-sulphate and butyrate-2-sulphate were significantly inhibitory.

Chemical Phenomena↗
PubMedDate not supplied

Arabidopsis mutations at the RPS2 locus result in loss of resistance to Pseudomonas syringae strains expressing the avirulence gene avrRpt2.

We isolated and characterized two Arabidopsis thaliana mutants that fail to mount a hypersensitive defense response (HR) when infiltrated with phytopathogenic Pseudomonas strains carrying the avirulence (avr) gene avrRpt2 but still mount an HR when infiltrated with strains carrying other avr genes. One of these mutants was isolated using a method we developed that enriches for Arabidopsis seedlings that survive vacuum-infiltration with a bacterial strain carrying an avr gene. Genetic analysis showed that the phenotypes of both mutants resulted from mutations at a single locus, RPS2. In contrast to the wild type, both rps2 mutants failed to limit the growth of Pseudomonas strains carrying avrRpt2. Heterozygous RPS2/rps2 plants displayed a phenotype intermediate between those of RPS2/RPS2 and rps2/rps2 homozygotes. These experiments show that the wild-type allele at the rps2 locus, RPS2, encodes a component of a signal transduction pathway that responds to a signal generated by avrRpt2 and that RPS2 is required for the elicitation of an HR. RPS2 was mapped near the restriction fragment length polymorphism marker PG11 on chromosome IV.

Arabidopsis↗
PubMed2003

Ethylene and jasmonic acid signaling affect the NPR1-independent expression of defense genes without impacting resistance to Pseudomonas syringae and Peronospora parasitica in the Arabidopsis ssi1 mutant.

Salicylic acid (SA), ethylene, and jasmonic acid (JA) are important signaling molecules in plant defense to biotic stress. An intricate signaling network involving SA, ethylene, and JA fine tunes plant defense responses. SA-dependent defense responses in Arabidopsis thaliana are mediated through NPR1-dependent and -independent mechanisms. We have previously shown that activation of an NPR1-independent defense mechanism confers enhanced disease resistance and constitutive expression of the pathogenesis-related (PR) genes in the Arabidopsis ssi1 mutant. In addition, the ssi1 mutant constitutively expresses the defensin gene PDF1.2. Moreover, SA is required for the ssi1-conferred constitutive expression of PDF1.2 in addition to PR genes. Hence, the ssi1 mutant appears to target a step common to SA- and ethylene- or JA-regulated defense pathways. In the present study, we show that, in addition to SA, ethylene and JA signaling also are required for the ssi1-conferred constitutive expression of PDF1.2 and the NPR1-independent expression of PR-1. Furthermore, the ethylene-insensitive ein2 and JA-insensitive jar1 mutants enhance susceptibility of ssi1 plants to the necrotrophic fungus Botrytis cinerea. However, defects in either the ethylene- or JA-signaling pathways do not compromise ssi1-conferred resistance to the bacterial pathogen Pseudomonas synringae pv. maculicola and the oomycete pathogen Peronospora parasitica. Interestingly, ssi1 exhibits a marginal increase in the levels of ethylene and JA, suggesting that low endogenous levels of these phytohormones are sufficient to activate expression of defense genes. Taken together, our results indicate that although cross talk in ssi1 renders expression of ethylene- or JA-responsive defense genes sensitive to SA and vice versa, it does not affect downstream signaling leading to resistance.

Arabidopsis↗
PubMed1976

Uronic acid dehydrogenase from Pseudomonas syringae. Purification and properties.

1. Uronic acid dehydrogenase was purified to homogeneity. After a 338-fold purification a yield of 16% was achieved with a specific activity of 81 mumol NADH formed min-1 mg protein-1. 2. The purity of the enzyme was controlled by disc electrophoresis, sodium dodecylsulfate electrophoresis and ultracentrifugation. 3. A molecular weight of 60 000 was determined by gel chromatography and by ultracentrifugation. 4. The native enzyme is composed of two subunits, their molecular weight being 30 000 as estimated by sodium dodecylsulfate electrophoresis. The subunits as such are inactive. 5. The absorption spectrum with a maximum at 278 nm shows no evidence for a prosthetic group. 6. For catalytic activity no SH groups and no metals seem to be necessary. 7. The Michaelis constants determined with the pure enzyme are for glucuronic acid Km = 0.37 mM, galacturonic acid Km = 54 muM and NAD+ (with glucuronic acid) Km = 80 muM. 8. A weak reverse reaction could be observed with glucaric acid lactones at acidic pH. 9. NADH is competitive with NAD+. The inhibitor constant is Ki = 60 muM. 10. The NAD+ binding site seems to be of lower specificity than the uronic acid binding site.

Aldehyde Oxidoreductases↗
PubMed1995

Product of fosC, a gene from Pseudomonas syringae, mediates fosfomycin resistance by using ATP as cosubstrate.

Pseudomonas syringe PB-5123, a producer of fosfomycin, is resistant to high concentrations of the antibiotic. Two possible mechanisms of resistance have been detected: (i) impermeability to exogenous fosfomycin, even in the presence of sugar phosphate uptake inducers, and (ii) antibiotic phosphorylation. The gene responsible for this last activity, fosC, encodes a ca. 19,000-Da protein and is immediately followed by a second open reading frame, which shows sequence similarities to glutathione S-transferases. FosC uses ATP as a cosubstrate in an inactivation reaction that can be reversed with alkaline phosphatase. Other nucleotide triphosphates cannot be substituted for ATP in this reaction. No relationship between fosC and the previously described genes of fosfomycin resistance was found.

Adenosine Triphosphate↗