VvNPR1.1 est l’orthologue d’AtNPR1 et sa surexpression provoque l’activation constitutive des gènes PR et la résistance à Erysiphe necator chez Vitis vinifera

La compréhension des bases moléculaires des mécanismes de résistance de la Vigne aux agresseurs biotiques constitue un prérequis à la recherche de moyens de lutte alternatifs aux pesticides. Chez Arabidopsis, NPR1 (Non expressor of PR genes 1) joue un rôle clé dans la voie de signalisation régulée par l’acide salicylique et responsable de la mise en place de la résistance aux agents pathogènes biotrophes et de la résistance systémique acquise (SAR). Nous avons identifié deux gènes homologues d’AtNPR1 chez la Vigne : VvNPR1.1 et VvNPR1.2. La caractérisation fonctionnelle de ces deux gènes montre que la surexpression de VvNPR1.1 dans le mutant npr1-2 d’Arabidopsis permet, contrairement `a VvNPR1.2, de restaurer l’expression de PR1 après traitement par du SA ou inoculation bactérienne, ainsi que la résistance à Pseudomonas syringae pv. maculicola, un agent pathogène virulent. VvNPR1.1 apparaît donc comme l’orthologue fonctionnel d’AtNPR1, alors que VvNPR1.2 assure vraisemblablement une fonction différente. La surexpression stable de VvNPR1.1 en fusion avec la GFP a également pu être réalisée chez V. vinifera cv. Chardonnay, grâce à une technique de transformation par A. tumefaciens de cals embryogènes de Vigne. Les résultats obtenus sur les plantules transformées montrent une localisation constitutive de VvNPR1-GFP dans le noyau, ainsi qu’une expression élevée des protéines PR en l’absence d’infection. De plus, les vignes surexprimant VvNPR1-GFP montrent clairement une augmentation de la r´esistance vis-à-vis de l’infection par Erysiphe necator, l’agent de l’oïdium. La forte conservation de séquence des gènes VvNPR1 chez les Vitaceae ainsi que l’ensemble de ces résultats souligne l’importance de la voie régulée par le SA et NPR1 pour la résistance aux agents pathogènes biotrophes chez la Vigne

Gypsophila paniculata root saponins as an environmentally safe treatment against two nematodes, natural vectors of grapevine fanleaf degeneration

International audienceBackground and Aims: Xiphinema index and X. diversicaudatum are nematodes that transmit the grapevine fanleaf virus and the Arabis mosaic virus, respectively. These viruses are the two agents mainly responsible for the disease that causes the most economic damage to grapevines worldwide. The infectious degeneration of grapevines affects vine performance and grape composition. The control of Xiphinema populations by soil disinfection is now impossible because of the removal from the market of the last available chemical treatments. In this study, saponins are assessed as an alternative treatment to control nematode populations. Methods and Results: The nematicidal effect of saponins from Gypsophila paniculata roots was tested against X. index and X. diversicaudatum. In aqueous media, a concentration of 1 mg/mL was associated with a mortality of greater than 95% in both nematodes, while in rearing soil, 73% of X. index and 85% of X. diversicaudatum were killed by 150 μg of saponins per gram of soil. In addition, an ecotoxicological study was undertaken on two soil bio-indicators (the mycorrhizal fungus Glomus mosseae and soil nitrification) that revealed that they were not affected by Gy. paniculata saponins at a nematicidal concentration. In the soil, investigation of the major Gy. paniculata root saponins revealed that these molecules were completely degraded in the soil within 4 days. Conclusion: We show that Gy. paniculata saponins are an efficient and environmentally friendly treatment against two nematodes that transmit grapevine fanleaf virus. Significance of the Study: This saponin-based alternative to chemical treatments could provide an environmentally safe and efficient solution for vine growers to use against grapevine fanleaf vector nematodes

Protoplasma

Botryosphaeria dieback, esca and Eutypa dieback are three economic major grapevine trunk diseases that cause severe yield reduction in vineyards worldwide. The frequency of disease symptoms has increased considerably over the past decade, and no efficient treatment is currently available to control these diseases. The different fungi associated with grapevine trunk diseases mainly induce necrotic wood and characteristic foliar symptoms. In this context, fungi virulence factors and host invasion are not well understood. We hypothesise that extracellular proteins produced by Diplodia seriata and Neofusicoccum parvum, two causal agents associated with Botryosphaeria dieback, are virulence factors responsible for the pathogenicity. In our previous work, we demonstrated that the total extracellular compounds produced by N. parvum induced more necrosis on Chardonnay calli and triggered a different defence gene expression pattern than those produced by D. seriata. Furthermore, this aggressiveness was not clearly correlated with the production of mellein, a characteristic phytotoxin of Botryosphaeriaceae, in our in vitro calli model. To characterise other potential virulence factors and to understand the mechanisms of host invasion by the fungus, we evaluated the profile, quantity and the impact of extracellular proteins produced by these fungi on Vitis vinifera calli necrosis and defence gene expression. Our results reveal that, under the same conditions, N. parvum produces more extracellular proteins and in higher concentrations than D. seriata. With Vitis vinifera cv. Chardonnay cells, we showed that equivalent concentrations of proteins secreted by N. parvum were more aggressive than those of D. seriata in producing necrosis and that they clearly induced more grapevine defence genes