Specific perception of ergosterol by plant cells

Ergosterol (a fungal membrane component) induced modification of proton fluxes and membrane yperpolarization in motor cells of Mimosa pudica. These reactions appear specific since they were not induced by the other sterols tested. A specific desensitization was observed, since cells did not react to a second ergosterol application. Exposed at first to other sterols, cells remained reactive to ergosterol. Comparatively, chitosan (a fungal wall component with known elicitor properties) triggered a membrane depolarization and also induced specific desensitization. This comparative study shows that ergosterol and chitosan are distinctly perceived by plant cells and induced different early events at the plasma membrane level

Transport des stérols et perception spécifique de l'ergostérol par la cellule végétale

Les stérols sont des composés très importants qui modulent des fonctions biologiques essentielles. Dans ce travail, les caractéristiques du transport membranaire des stérols ont été déterminées en suivant l'absorption du cholestérol radiomarqué par les tissus foliaires de betterave sucrière. Les résultats obtenus montrent que cette absorption présente une composante active, est sous le contrôle du métabolisme général des cellules puits et nécessite l'intervention d'une composante protéique. Des expériences de compétition ont montré que l'absorption est spécifique de ce type de composés. De plus, les données obtenues suggèrent que le transport des stérols ne se réalise ni par un cotransport proton/stérol ni par un transporteur de type ABC. Les stérols perturbent peu les flux de protons et modifient peu le potentiel transmembranaire. Seul, l'ergostérol (stérol spécifiquement fongique) induit des réactions originales : alcalinisation transitoire du milieu d'incubation, hyperpolarisation de la membrane plasmique. L'ergostérol induit la bouffée oxydative et active des enzymes intervenant dans ce phénomène. Cependant, l'ergostérol a peu d'effet sur l'activité de la phénylalanine ammonia lyase.Sterols are important compounds mediating essential biological functions. Informations concerning sterol absorption by plant cells are lacking. In this work, the characteristics of cholesterol membrane transport are determined by following the uptake of [3H]-cholesterol in leaf tissues of sugar beet. The uptake was shown to be an active process controlled by the cell metabolism and achieved through a protein component. Competition experiments showed that the uptake is specific for this class of molecules. Moreover, data suggest that sterol transport did not involve a proton/sterol cotransport or an ABC transporter. Sterols did not disturb proton fluxes and showed a reduced effect on the transmembrane potential. Ergosterol, a specific fungal sterol, showed particular effects: transient alcalinization in the incubation medium and membrane hyperpolarization. Its action also induced oxidative burst and enzyme activations. By contrast, ergosterol induced a slight effect on the phenylalanine ammonia lyase activity, suggesting that this sterol is not strongly implicated in phenylpropanoid synthesis.POITIERS-BU Sciences (861942102) / SudocSudocFranceF

Systemic Induction of the Defensin and Phytoalexin Pisatin Pathways in Pea (Pisum sativum) against Aphanomyces euteiches by Acetylated and Nonacetylated Oligogalacturonides

International audienceOligogalacturonides (OGs) are known for their powerful ability to stimulate the plant immune system but little is known about their mode of action in pea (Pisum sativum). In the present study, we investigated the elicitor activity of two fractions of OGs, with polymerization degrees (DPs) of 2–25, in pea against Aphanomyces euteiches. One fraction was nonacetylated (OGs − Ac) whereas the second one was 30% acetylated (OGs + Ac). OGs were applied by injecting the upper two rachises of the plants at three- and/or four-weeks-old. Five-week-old roots were inoculated with 105 zoospores of A. euteiches. The root infection level was determined at 7, 10 and 14 days after inoculation using the quantitative real-time polymerase chain reaction (qPCR). Results showed significant root infection reductions namely 58, 45 and 48% in the plants treated with 80 µg OGs + Ac and 59, 56 and 65% with 200 µg of OGs − Ac. Gene expression results showed the upregulation of genes involved in the antifungal defensins, lignans and the phytoalexin pisatin pathways and a priming effect in the basal defense, SA and ROS gene markers as a response to OGs. The reduction of the efficient dose in OGs + Ac is suggesting that acetylation is necessary for some specific responses. Our work provides the first evidence for the potential of OGs in the defense induction in pea against Aphanomyces root rot

Characterization of sterol uptake in leaf tissues of sugar beet

International audienc

Systemic Induction of the Defensin and Phytoalexin Pisatin Pathways in Pea (Pisum sativum) against Aphanomyces euteiches by Acetylated and Nonacetylated Oligogalacturonides

Oligogalacturonides (OGs) are known for their powerful ability to stimulate the plant immune system but little is known about their mode of action in pea (Pisum sativum). In the present study, we investigated the elicitor activity of two fractions of OGs, with polymerization degrees (DPs) of 2–25, in pea against Aphanomyces euteiches. One fraction was nonacetylated (OGs − Ac) whereas the second one was 30% acetylated (OGs + Ac). OGs were applied by injecting the upper two rachises of the plants at three- and/or four-weeks-old. Five-week-old roots were inoculated with 105 zoospores of A. euteiches. The root infection level was determined at 7, 10 and 14 days after inoculation using the quantitative real-time polymerase chain reaction (qPCR). Results showed significant root infection reductions namely 58, 45 and 48% in the plants treated with 80 µg OGs + Ac and 59, 56 and 65% with 200 µg of OGs − Ac. Gene expression results showed the upregulation of genes involved in the antifungal defensins, lignans and the phytoalexin pisatin pathways and a priming effect in the basal defense, SA and ROS gene markers as a response to OGs. The reduction of the efficient dose in OGs + Ac is suggesting that acetylation is necessary for some specific responses. Our work provides the first evidence for the potential of OGs in the defense induction in pea against Aphanomyces root rot

Inter-calibration de spectromètres NIRS pour la prédiction du Carbone et de l’Azote dans les sols

National audienc