Genetic dissection of the tissue-specific roles of type III effectors and phytotoxins in the pathogenicity of Pseudomonas syringae pv. syringae to cherry

When compared with other phylogroups (PGs) of the Pseudomonas syringae species complex, P. syringae pv. syringae (Pss) strains within PG2 have a reduced repertoire of type III effectors (T3Es) but produce several phytotoxins. Effectors within the cherry pathogen Pss 9644 were grouped based on their frequency in strains from Prunus as the conserved effector locus (CEL) common to most P. syringae pathogens; a core of effectors common to PG2; a set of PRUNUS effectors common to cherry pathogens; and a FLEXIBLE set of T3Es. Pss 9644 also contains gene clusters for biosynthesis of toxins syringomycin, syringopeptin and syringolin A. After confirmation of virulence gene expression, mutants with a sequential series of T3E and toxin deletions were pathogenicity tested on wood, leaves and fruits of sweet cherry (Prunus avium) and leaves of ornamental cherry (Prunus incisa). The toxins had a key role in disease development in fruits but were less important in leaves and wood. An effectorless mutant retained some pathogenicity to fruit but not wood or leaves. Striking redundancy was observed amongst effector groups. The CEL effectors have important roles during the early stages of leaf infection and possibly acted synergistically with toxins in all tissues. Deletion of separate groups of T3Es had more effect in P. incisa than in P. avium. Mixed inocula were used to complement the toxin mutations in trans and indicated that strain mixtures may be important in the field. Our results highlight the niche-specific role of toxins in P. avium tissues and the complexity of effector redundancy in the pathogen Pss 9644.

Removal of a component interfering with phosphatidylglycerol estimation in the "Helena" system for amniotic fluid phospholipids

A simple " prechromatography " step removes a component of amniotic fluid ("pseudo PG") that otherwise co-chromatographs with phosphatidylglycerol in the system for amniotic fluid analysis developed by Touchstone et al. (Lipids 15: 61-62, 1980) and incorporated into the Helena "Fetal-Tek" kit. The final positions of the major phospholipids are practically unchanged but the faster migrating, more neutral components are swept into a tight band near the solvent front, providing improved general resolution. The resulting change in the ratio of "phosphatidylglycerol" to sphingomyelin ("PG"/S) is as much as 0.5 for some specimens, but no change is seen for others. In 20% of the 73 cases examined, including four of the six fluids associated with respiratory distress syndrome, the PG initially reported was found to be "pseudo PG" and was completely removed by the prechromatography step. This step produces a negligible decrease in the lecithin to sphingomyelin (L/S) ratio in amniotic fluid.

Removal of a component interfering with phosphatidylglycerol estimation in the "Helena" system for amniotic fluid phospholipids

A simple " prechromatography " step removes a component of amniotic fluid ("pseudo PG") that otherwise co-chromatographs with phosphatidylglycerol in the system for amniotic fluid analysis developed by Touchstone et al. (Lipids 15: 61-62, 1980) and incorporated into the Helena "Fetal-Tek" kit. The final positions of the major phospholipids are practically unchanged but the faster migrating, more neutral components are swept into a tight band near the solvent front, providing improved general resolution. The resulting change in the ratio of "phosphatidylglycerol" to sphingomyelin ("PG"/S) is as much as 0.5 for some specimens, but no change is seen for others. In 20% of the 73 cases examined, including four of the six fluids associated with respiratory distress syndrome, the PG initially reported was found to be "pseudo PG" and was completely removed by the prechromatography step. This step produces a negligible decrease in the lecithin to sphingomyelin (L/S) ratio in amniotic fluid.

Influence of phospholipid saturation on classical thin-layer chromatographic detection methods and its effect on amniotic fluid lecithin/sphingomyelin ratio determinations

We compared seven techniques, commonly used for detection of amniotic fluid phospholipids in thin-layer chromatography, with respect to their sensitivity to saturation of the fatty acid carbon-chain of lecithin. The techniques fell into two classes: sensitive and insensitive; those classed as saturation sensitive were less than or equal to 10% as sensitive to fully saturated lecithin as to lecithin with singly unsaturated acid moieties. Color development increased with the number of carbon-carbon double bonds per molecule but required only a single unsaturated acid ester in either the alpha or the beta position. Mixtures of lecithins with defined saturation, when detected by saturation-sensitive methods, mimicked the uneven coloration of amniotic fluid lecithin bands, supporting the hypothesis that this uneven coloration results from natural saturation heterogeneity. Detection techniques representative of these classes are shown to give widely differing values for the lecithin/sphingomyelin ratio for actual specimens of amniotic fluid.

Influence of phospholipid saturation on classical thin-layer chromatographic detection methods and its effect on amniotic fluid lecithin/sphingomyelin ratio determinations

We compared seven techniques, commonly used for detection of amniotic fluid phospholipids in thin-layer chromatography, with respect to their sensitivity to saturation of the fatty acid carbon-chain of lecithin. The techniques fell into two classes: sensitive and insensitive; those classed as saturation sensitive were less than or equal to 10% as sensitive to fully saturated lecithin as to lecithin with singly unsaturated acid moieties. Color development increased with the number of carbon-carbon double bonds per molecule but required only a single unsaturated acid ester in either the alpha or the beta position. Mixtures of lecithins with defined saturation, when detected by saturation-sensitive methods, mimicked the uneven coloration of amniotic fluid lecithin bands, supporting the hypothesis that this uneven coloration results from natural saturation heterogeneity. Detection techniques representative of these classes are shown to give widely differing values for the lecithin/sphingomyelin ratio for actual specimens of amniotic fluid.