Sémiologie, innovation et entreprise – Colloque de l’Anvie 9-10 décembre 1998

« Sémiologie, Innovation et Entreprise » tel était le thème du colloque des 9 et 10 décembre qui faisait suite à un premier colloque organisé par l’ANVIE en février 1996, intitulé « Sémiologie et Entreprise », ouvrant dès lors le débat sur la présence et les applications de cette discipline universitaire au champ pragmatico-commercial de l’entreprise. Étaient présentes près de 250 personnes. Les intervenants, au nombre de 50, étaient des professionnels (consultants, responsables d’entreprises..

Identification and characterization of a triacylglycerol lipase in Arabidopsis homologous to mammalian acid lipases

AbstractTriacylglycerol (TAG) lipases have been thoroughly characterized in mammals and microorganisms. By contrast, very little is known on plant TAG lipases. An Arabidopsis cDNA called AtLip1 (At2g15230), which exhibits strong homology to lysosomal acid lipase, was found to drive the synthesis of an active TAG lipase when expressed in the baculovirus system. The lipase had a maximal activity at pH 6 and the specific activity was estimated to be about 45μmolmin−1mg−1 protein using triolein as a substrate. Knock-out mutant analysis showed no phenotype during germination indicating that this enzyme is fully dispensable for TAG storage breakdown during germination. Northern blot analyses indicated that the transcript is present in all tissues tested

Purification and antipathogenic activity of lipid transfer proteins (LTPs) from the leaves of Arabidopsis and spinach

Two homogeneous proteins active in vitro against the bacterial pathogen Clavibacter michiganensis subsp. sepedonicus were obtained from a crude cell-wall preparation from the leaves of Columbia wild-type Arabidopsis. The N-terminal amino acid sequences of these proteins allowed their identification as lipid transfer proteins (LTP-a1, LTP-a2); the LTP1-a1 sequence was identical to that deduced from a previously described cDNA (EMBL M80566) and LTP-a2 was quite divergent (44% identical positions). These proteins were not detected in the cytoplasmic fraction by Western-blot analysis. Proteins LTP-s1 and LTP-s2 were similarly obtained from spinach leaves; LTP-s1 was 91% identical to a previously purified spinach LTP (Swiss Prot P10976), and LTP-s2 was moderately divergent (71% identical positions). About of the total LTPs were detected in the cytoplasmic fraction from spinach by Westem-blot analysis. Concentrations of these proteins causing 50% inhibition (EC-50) were in the 0.1–1 μM range for the bacterial pathogens C. michiganensis and Pseudomonas solanacearum and close to 10 μM for the fungal pathogen Fusarium solani

New low electron flux facility in the 0 to 3.5 MeV range for the study of induced signal in JUICE instruments: UVS and MAJIS measurements

We designed and built a new test facility to investigate signal induced by electrons in the 0-3.5 MeV in the JUICE UVS and MAJIS instruments. The facility uses radioisotopes sources to produce low flux of electrons (< 6000 electrons/cm².s). We present the facility, its capabilities and the results of measurements on UVS and MAJIS

Isolation of a Δ5-fatty acid desaturase gene from Mortierella alpina

Arachidonic acid (C20:4 Δ5,8,11,14)) is a polyunsaturated fatty acid synthesized by the ?-fatty acid desaturation of di-homo-?-linolenic acid (C20:3 Δ8,11,14)). In mammals, it is known to be a precursor of the prostaglandins and the leukotrienes but it is also accumulated by the filamentous fungus Mortierella alpina. We have isolated a cDNA encoding the Δ5-fatty acid desaturase from M. alpina via a polymerase chain reaction- based strategy using primers designed to the conserved histidine box regions of microsomaL desaturases, and confirmed its function by expression in the yeast Saccharomyces cerevisiae. Analysis of the lipids from the transformed yeast demonstrated the accumulation of arachidonic acid. The M. alpina Δ5- desaturase is the first example of a cloned Δ5-desaturase, and differs from other fungal desaturases previously characterized by the presence of an N- terminal domain related to cytochrome b5

A tomato xylem sap protein represents a new family of small cysteine-rich proteins with structural similarity to lipid transfer proteins

AbstractThe coding sequence of a major xylem sap protein of tomato was identified with the aid of mass spectrometry. The protein, XSP10, represents a novel family of extracellular plant proteins with structural similarity to plant lipid transfer proteins. The XSP10 gene is constitutively expressed in roots and lower stems. The decline of XSP10 protein levels in tomato infected with a fungal vascular pathogen may reflect breakdown or modification by the pathogen

The tomato xylem sap protein XSP10 is required for full susceptibility to Fusarium wilt disease

XSP10 is an abundant 10 kDa protein found in the xylem sap of tomato. The protein displays structural similarity to plant lipid transfer proteins (LTPs). LTPs are involved in various physiological processes, including disease resistance, and some are able to bind and transfer diverse lipid molecules. XSP10 abundance in xylem sap declines upon infection with Fusarium oxysporum f. sp. lycopersici (Fol), implying involvement of XSP10 in the plant–pathogen interaction. Here, the biochemical characterization of XSP10 with respect to fatty acid-binding properties is reported; a weak but significant binding to saturated fatty acids was found. Furthermore, XSP10-silenced tomato plants were engineered and it was found that these plants exhibited reduced disease symptom development upon infection with a virulent strain of Fol. Interestingly, the reduced symptoms observed did not correlate with an altered expression profile for known reporter genes of plant defence (PR-1 and WIPI). This work demonstrates that XSP10 has lipid-binding properties and is required for full susceptibility of tomato to Fusarium wilt

The defensive role of nonspecific lipid-transfer proteins in plants

Plant nonspecific lipid-transfer proteins stimulate the transfer of a broad range of lipids between membranes in vitro. In view of their ability to inhibit bacterial and fungal pathogens, their distribution at high concentrations over exposed surfaces and in the vascular system, and the response of Ltp-gene expression to infection with pathogens, they are now thought to be active plant-defense proteins