Mécanismes de la réponse adaptative du rosier miniature aux stress abiotiques (aspects fondamentaux et appliqués)

Métaflore produit des rosiers miniatures en mode cultural court (MCC), mais aussi en mode cultural long (MCL), avec un arrêt végétatif pendant la saison froide. Ce stress hivernal permet l'édification d'une charpente trapue, que nous tentons d'obtenir en MCC en appliquant divers stress abiotiques. Les stress abiotiques activent l'expression de la Cu/Zn-superoxyde dismutas. Le stress mécanique augmente les isoformes à 20, 17 et 15 kDa, le stress hydrique celles à 17 et 15 kDa, alors que le MCL et le stress chimique n'activent que l'isoforme à 17 kDa. Western- et Northern blots ont montré l'expression biphasique de la Cu/Zn-SOD. Nous l'avons immunodétectée dans plusieurs compartiments en particulier dans la membrane plasmique des CAVs. Sur le plan appliqué, notre objectif visant à obtenir une charpente trapue et ramifiée est en partie atteint en utilisant un stress hydrique. D'un point de vue fondamental, nos résultats mettent en évidence le rôle régulateur de la CAV dans la fonction de puits transitoire du xylème caulinaire.METAFLORE miniature rose-bush production can be in either short growth mode (SGM) or long growth mode (LGM), including a growth stoppage during winter. This winter stress enables plants to develop a well-lignified frame, that we try to obtain applying abiotic stresses on SGM. Abiotic stresses activate expression of the Cu/Zn-superoxide dismutase. The mechanical stress increases isoforms at 20, 17, 15 kDa, the water deficit that at 17 and 15 kDa, but LGM and chemical stress only the isoform at 17 kDa. Western and Northern blots have indicated biphasic expression of the Cu/Zn-SOD. We have immunodetected this enzyme in several compartments, in particular in the plasma membrane of the VACs. In application, our objective of obtaining well lignified frame using water deficit is met in part. From a fundamental point of view, our results highlight the regulatory role of the VAC in the transitory sink function played by the stem xylem.POITIERS-BU Sciences (861942102) / SudocSudocFranceF

DIAGNOSIS OF EUTYPA LATA INFECTION IN GRAPEVINES BY SEROLOGICAL DETECTION OF SECRETED POLYPEPTIDES

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Biologie des agents de l'esca et impacts sur la vigne (Vitis vinefera L. cv Ugni blanc)

L esca est une maladie de dépérissement de la vigne provoquée par des champignons intraxylémiens, dont Phaeomoniella chlamydospora et Phaeoacremonium aleophilum. Nous avons tout d abord précisé l influence de facteurs environnementaux tels que la température et le pH sur la croissance des deux champignons et défini des critères cyto-physiologiques permettant leur distinction in vitro. A l issue de leur étude in planta, dans des boutures infectées sélectivement, nous avons observé que ces agents colonisent des tissus distincts : P. chlamydospora se développe essentiellement dans les vaisseaux et les fibres xylémiennes alors que P. aleophilum est détecté préférentiellement dans le protoxylème et la moelle. Ce dernier présente une capacité de dégradation des différentes couches pariétales lignifiées alors que P. chlamydospora ne désorganise que les parois pectocellulosiques. De plus, des expériences de co-inoculation montrent l effet synergique des deux champignons dans leur capacité d envahissement du xylème et d altération des parois. Sur les sarments et les feuilles de Vitis vinifera cv Ugni blanc nous avons défini des caractéristiques phénotypiques et structurales propres à l esca, comparativement à celles du black dead arm et de l eutypiose. Puis, dans les feuilles nous avons mis en évidence l impact de l esca sur le glutathion et sur l expression des gènes d enzymes participant à son métabolisme, dont des glutathion S-transférases. Au delà des altérations précoces du métabolisme primaire, la teneur et l état rédox du glutathion et l expression des glutathion S-transférases représentent des marqueurs de niveau de stress dans la vigne : leur suivi pourrait être un indicateur de l apparition de la maladie au vignoble.Esca disease is a grapevine damage induced by pathogenic fungi localized in the xylem especially Phaeomoniella chlamydospora and Phaeoacremonium aleophilum. We evaluated the effect of various environmental factors, such as temperature and pH on the development of these two fungal pathogens and determined the corresponding cyto-physiological criteria leading to their in vitro characterization. In selectively infected cuttings we observed that these agents invaded different areas: P. chlamydospora developed mainly in vessels and fibres whereas P. aleophilum was detected predominantly in protoxylem and pith areas. Our data also highlighted P. aleophilum capacity to degrade lignified wall layers whereas P. chlamydospora only disorganized pectocellulose walls. In addition, co-inoculations of the two fungi showed the synergistic capacity of these two fungi to invade wood and cause cell wall damage. In canes and leaves of Vitis vinifera cv Ugni blanc we determined specific phenotypic and structural features of the esca disease and compared this to those of black dead arm and eutypa dieback. We observed the impact of esca on glutathione in leaves, focusing on gene expression corresponding to enzymes involved in its metabolism, as well as glutathione S-transferases. Apart from an initial perturbation in primary metabolism, levels and redox state of glutathione and expression of glutathione S-transferases can be considered as stress markers in vine: their detection might constitute an early indicator for infection of grapevine by esca disease in the field.POITIERS-BU Sciences (861942102) / SudocSudocFranceF

Characteristic early membrane effects induced by tryptophan in pulvinar motor cells

International audienceTryptophan at concentrations higher than 0.1 mM, triggered characteristic early physiological effects such as rapid (within 5 min) dose-dependent membrane hyperpolarization in Mimosa pudica motor cells and modification of the time course of the spontaneous proton efflux monitored in the incubation medium of pulvinar tissues. The rapid modifications of the leaf turgor-mediated movements seen on the primary pulvini of M. pudica following a shock and on Cassia fasciculata leaflets during a transition from light to darkness indicate that tryptophan disturbed the ionic migrations involved in the electrophysiological events and in the osmocontractile reaction of the motor cells. These reactions were specific to tryptophan compared to those induced by serine and 5-hydroxytryptophan. The tryptophan mode of action cannot be linked to a direct modification of the plasma membrane H+-ATPase activity as monitored on purified pulvinar plasma membrane vesicles. The tryptophan metabolism-linked products tryptamine and indole also inhibited the motile reactions, activated in a continuous manner the H+ secretion of pulvinar tissues and showed properties of a protonophore and an ATPase activity inhibitor on plasma membrane vesicles, respectively. The specific behavior of tryptophan in the reaction studies here is discussed in light of the previously reported action of phytohormones

Antifungal effects of iron sulfate on grapevine fungal pathogens

International audienceThe present study aimed to determine the most efficient experimental conditions of iron sulfate use leading to optimal inhibition in the development of fungal pathogens. Assays have been focused on fungal species inducing severe grapevine diseases. FeSO4 directly inhibited the in vitro mycelial growth of Botrytis cinerea, Eutypa lata, Phaeomoniella chlamydospora, Phaeoacremonium aleophilum, Diplodia seriata, and Neofusicoccum parvum with variable efficiency in the range of 0.5-10 mM. The development was always completely inhibited at 20 mM. This inhibitory effect was greatly increased at acidic pH values. The anionic moiety of the molecule was of importance since bromide, chloride and sulfate were highly active, whereas acetate and oxalate showed a small effect. Electron microscope observations on E. lata and B. cinerea showed that a treatment with FeSO4 induced dramatic changes in the hyphal organization leading to cell death. No toxicity was observed on grapevine leaves following repeated FeSO4 sprays in the antifungal concentration range. Therefore, FeSO4 may be proposed to effectively replace the long-term pollutant use of CuSO4 as an antifungal agent, with the additional advantage of iron being an important plant micronutrient

Inhibitory effects of polypeptides secreted by the grapevine pathogens Phaeomoniella chlamydospora and Phaeoacremonium aleophilum on plant cell activities

International audienceEsca is a devastating disease affecting grapevines all around the world induced by a complex of xylem-inhabiting fungi. In order to elucidate the mechanisms of virulence of the esca-associated fungi Phaeomoniella chlamydospora (Pch) and Phaeoacremonium aleophilum (Pal), the phytotoxic activities of the polypeptides secreted in their culture medium were investigated. Both polypeptide fractions (PFs), which are composed of proteins with an apparent molecular mass ranging from 6 to 250 kDa, triggered the death of grapevine 41BT cells in culture and induced transitory H+ flux modifications and membrane depolarization of cells. Complementary assays with plasma membrane vesicles showed that the H+-ATPase is targeted by these polypeptides, as shown by the inhibition of the enzyme catalytic activity and the decrease of proton conductance of plasma membrane. Due to this impairment, an inhibition of uptake of assimilates occurred. Furthermore, PFs also induced the activation of the plant secondary metabolism as indicated by induction of the anthocyanin synthesis. In addition, PFs acted on key enzyme reactions known to participate to the elicitation process, namely NADPH oxidase and phenylalanine ammonia-lyase (PAL). Considering the differential effect of the PF secreted respectively by Pch and Pal on the latter enzymes, it could be hypothesized that the toxic polypeptides of the two fungi modify the plant cell metabolism by different pathways, hence indicating that the proteinaceous compounds secreted by both esca-associated fungi Pch and Pal may act as virulence factors

Towards a preventive and/or curative treatment of esca in grapevine trunk disease: General basis in the elaboration of treatments to control plant pathogen attacks

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