Jacques Bernillon

Biosynthesis of mycosporines: Mycosporine glutaminol in Trichothecium roseum

The Deuteromycete Trichothecium roseum produces significant amounts of mycosporine glutaminol during its sporulation phase. This production is improved when glucose is substituted by quinic acid in the culture medium. Data from the incorporation of [1–−14C]acetic acid, [1–14C]glyceric acid and [U–14C]3-dehydroquinic acid are in very good agreement with the C6-C1 unit (cyclohexenone) of fungal mycosporines originating from the first part of the shikimate pathway.

Conservation of the links between gene transcription and chromosomal organization in the highly reduced genome of Buchnera aphidicola

BackgroundGenomic studies on bacteria have clearly shown the existence of chromosomal organization as regards, for example, to gene localization, order and orientation. Moreover, transcriptomic analyses have demonstrated that, in free-living bacteria, gene transcription levels and chromosomal organization are mutually influenced. We have explored the possible conservation of relationships between mRNA abundances and chromosomal organization in the highly reduced genome of Buchnera aphidicola, the primary endosymbiont of the aphids, and a close relative to Escherichia coli.ResultsUsing an oligonucleotide-based microarray, we normalized the transcriptomic data by genomic DNA signals in order to have access to inter-gene comparison data. Our analysis showed that mRNA abundances, gene organization (operon) and gene essentiality are correlated in Buchnera (i.e., the most expressed genes are essential genes organized in operons) whereas no link between mRNA abundances and gene strand bias was found. The effect of Buchnera genome evolution on gene expression levels has also been analysed in order to assess the constraints imposed by the obligate symbiosis with aphids, underlining the importance of some gene sets for the survival of the two partners. Finally, our results show the existence of spatial periodic transcriptional patterns in the genome of Buchnera.ConclusionDespite an important reduction in its genome size and an apparent decay of its capacity for regulating transcription, this work reveals a significant correlation between mRNA abundances and chromosomal organization of the aphid-symbiont Buchnera.

Mycosporine glutamine and related mycosporines in the fungus Pyronema omphalodes

Abstract The structure of mycosporine glutamine, a new compound, has been established and its presence demonstrated in two fungi Pyronema omphalodes and Glomerella cingulata. Mycosporine glutamic acid has been isolated from Helvella leucomelaneae. Co-occurrence of normycosporine glutamine, mycosporine glutamine and glucosylmycosporine glutaminol has been demonstrated in the fungus P. omphalodes. A biosynthetic pathway is proposed. Mycosporines have been compared by HPLC.

Structure du stearyl-velutinal, sequiterpenoide naturel de lactarius velutinus bert1.

Stearyl-velutinal, a new natural sesquiterpenoid isolated from lactarius velutinus Bert., has the structure 1; this very labile compound is responsible for the dark-blue reation of the fungus to the ‘sulfo-vanilic’ mixtures.

Mycosporins from Ascochyta pisi, Cladosporium herbarum and Septoria nodorum

Abstract The chemical structure of the mycosporin isolated from Ascochyta pisi, Cladosporium herbarum and Septoria nodorum was established as mycosporin-2 glucoside.

Specificity of Pseudomonas aeruginosa serralysin revisited, using biologically active peptides as substrates

The characterization of the specificity of alkaline protease from Pseudomonas aeruginosa has not yet been clearly defined. Some previous results suggested that its specificity was influenced more by amino acids far from the hydrolyzed peptide bond, than by amino acids in P1 or P1 position. From other data, it was a C-(COOH)-type endoprotease where the preferential amino acid in P1 position was an arginine residue. We have studied the hydrolysis of several biologically active peptides. Many various sites of cleavage have been characterized but no arginine in P1 position was found, despite the presence of arginine in the peptide sequence. In fact P1 and P1 position could be occupied by various amino acids. It seems unlikely that Pseudomonas alkaline protease may only be considered as a protease specific to arginine in P1 position. On the other hand, we have observed that increase of the peptide chain length led to an important increase of the hydrolysis rate, suggesting an extended number of subsites.

Highly oxygenated flavones from Mentha piperita

Abstract Six highly oxygenated flavones have been isolated from the leaves of Mentha piperita . Five known compounds, 5-hydroxy-6,7,8,4′-tetramethoxyflavone, 5,4′-dihydroxy-6,7,8-trimethoxyflavone, 5,3′-dihydroxy-6,7,8,4′-tetramethoxyflavone, 5-hydroxy-6,7,8,3′,4′-pentamethoxyflavone and 5,3′,4′-trihydroxy-6,7,8-trimethoxyflavone, are reported for the first time in the genus Mentha . The sixth compound has been identified as 5,6-dihydroxy-7,8,3′,4′-tetramethoxyflavone by UV, NMR and mass spectra.

Sur la presence de mycosporines-glutamine reduites, nouvelles molecules, chez plusieurs deuteromycetes.

Resume The isolation and structures of new widespread mycosporine reduced-glutamine ( 3 ) and its glucoside ( 4 ) are described. HPLC and new MS improvements (FABS and direct HPLC-MS coupling) provide convenient methods for the study of these unstable compounds.

Use of a 49-peptide library for a qualitative and quantitative determination of pseudomonal serralysin specificity

The Pseudomonas aeruginosa serralysin (E.C. 3.4.24.40.), which is a zinc-dependent metalloprotease from the metzincin superfamily, has quite a broad specificity, which has not yet been clearly identified. We have studied it with an original approach, using a 49-peptide library of the type Z-AXXA (amide) (X = A, L, V, F, S, R, E). The library was analyzed by LC-MS before and after enzymatic hydrolysis. A great number of hydrolyzed peptides were screened and the preferential hydrolysis was the X-X peptide bond, even if in some cases, A-X and X-A bond could be hydrolyzed. No amino acids with a ionized side chain could be found in the P1 position. The results obtained suggest that the specificity in the P1 position, where an hydrophobic residue was preferentially found, seems more selective that in the Pn position. The P1 position was not very specific, but, on a quantitative point of view, the enzymatic activity was particularly increased when R, F or A were in this position. The results allow us to define the P1 and P1 residues for an optimal substrate of pseudomonal serralysin and usable for the design and the synthesis of a specific inhibitor.

Open and ring forms of mycosporin-2 from the ascomycete Gnomonia leptostyla

Abstract The three reproductive forms of Gnomonia leptostyla synthesize mycosporin-2 ring and open forms. The chemical structures were determined from NMR and MS data.