Synthese des acides beta-fluoroglutamiques et utilisation pour l'etude de reactions enzymatiques mettant en jeu l'acide glutamique

SIGLECNRS T 54627 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Contribution à l'étude du métabolisme de la chitine chez le champignon phytopathogène botrytis cinerea

PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Survey of the Botrytis cinerea chitin synthase multigenic family through the analysis of six euascomycetes genomes

International audienceWe describe a strategy for systematic amplification of chitin synthase genes (chs) in the filamentous ascomycetes plant-pathogen Botrytis cinerea using PCR with multiple degenerate primers designed on specific and conserved sequence motifs. Eight distinct chs genes were isolated, named Bcchs I, II, IIIa, IIIb, IV, V, VI and VII. They probably constitute the entire chs multigenic family of this fungus, as revealed by careful analysis of six euascomycetes genomes. Bcchs I, IIIa, IIIb, IV and VI genes were subjected to DNA walking and their deduced amino acid sequences were compared by hydrophobic cluster analysis (HCA) to localize putative residues critical for CHS activity. HCA also enabled us to highlight three different transmembrane topologies of the CHS membranous isoenzymes. We found that the N-terminal region of the BcCHSI isoenzyme, and its orthologues in other euascomycetes, probably contain folded peptide motifs with conserved tyrosine residues. Their putative role is discussed. The BcCHSVII isoenzyme appeared to belong to a new class of CHS orthologues that was demonstrated by phylogenetic study to branch apart from division 1 and 2 of CHS

Impact of cocoa processing technologies in free fatty acids formation in stored raw cocoa beans

The quality of raw cocoa beans depends widely on their free fatty acids (FFA) content. High FFA content is a serious quality defect and reduces the technical and economic value of the cocoa beans. The work investigates the influence of cocoa processing technologies on FFA formation during storage of raw cocoa beans. Different samples of ferment dried cocoa beans purchased from Cote d'Ivoire were stored and analysed for FFA content. Very low FFA contents were found in whole healthy cocoa beans generally complied with UE standards (1.75% oleic acid equivalent) throughout storage while high FFA content was found in poor quality and broken healthy beans. The formation of FFA did not depend on the genotype or on cocoa post-harvest processing technologies. However, high and increasing FFA contents were observed in defective cocoa beans and could be attributed probably to the activity of microflora which in turn were associated with initial quality and loss of physical integrity of the cocoa beans

Exocomets size distribution in the β ? Pictoris planetary system

International audienceThe star β ? Pictoris harbors a young planetary system of about 20 million years old, which is characterized by the presence of a gaseous and dusty debris disk, at least two massive planets and many minor bodies. For more than thirty years, exocomets transiting the star have been detected using spectroscopy, probing the gaseous part of the cometary comas and tails. The detection of the dusty component of the tails can be performed through photometric observations of the transits. Since 2018, the Transiting Exoplanet Survey Satellite has observed β ? Pic for a total of 156 days. Here we report an analysis of the TESS photometric data set with the identification of a total of 30 transits of exocomets. Our statistical analysis shows that the number of transiting exocomet events (N) as a function of the absorption depth (AD) in the light curve follows a power law in the form d N (A D ) ∝A D-α ?, where α =2.3 ±0.4 ?. This distribution of absorption depth leads to a differential comet size distribution proportional to R-γ?, where γ =3.6 ±0.8 ?, showing a striking similarity to the size distribution of comets in the Solar system and the distribution of a collisionally relaxed population (γD=3.5 ?)