The grapevine (Vitis vinifera) LysM receptor kinases VvLYK1-1 and VvLYK1-2 mediate chitooligosaccharide-triggered immunity

Chitin, a major component of fungal cell walls, is a well-known pathogen-associated molecular pattern (PAMP) that triggers defense responses in several mammal and plant species. Here, we show that two chitooligosaccharides, chitin and chitosan, act as PAMPs in grapevine (Vitis vinifera) as they elicit immune signalling events, defense gene expression and resistance against fungal diseases. To identify their cognate receptors, the grapevine family of LysM receptor kinases (LysM-RKs) was annotated and their gene expression profiles were characterized. Phylogenetic analysis clearly distinguished three V. vinifera LysM-RKs (VvLYKs) located in the same clade as the Arabidopsis CHITIN ELICITOR RECEPTOR KINASE1 (AtCERK1), which mediates chitin-induced immune responses. The Arabidopsis mutant Atcerk1, impaired in chitin perception, was transformed with these three putative orthologous genes encoding VvLYK1-1, -2, or -3 to determine if they would complement the loss of AtCERK1 function. Our results provide evidence that VvLYK1-1 and VvLYK1-2, but not VvLYK1-3, functionally complement the Atcerk1 mutant by restoring chitooligosaccharide-induced MAPK activation and immune gene expression. Moreover, expression of VvLYK1-1 in Atcerk1 restored penetration resistance to the non-adapted grapevine powdery mildew (Erysiphe necator). On the whole, our results indicate that the grapevine VvLYK1-1 and VvLYK1-2 participate in chitin- and chitosan-triggered immunity and that VvLYK1-1 plays an important role in basal resistance against E. necator

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The xyloglucans : are they new elicitors of Arabidopsis thaliana immunity ?

Damaged-Associated Molecular Patterns (DAMPs) are endogenous molecules released from the plant cell wall after wounding by pathogens. DAMPs are recognized by Pattern- Recognition Receptors (PRRs) that play a key role in plant immunity by mediating defense responses. The plant cell wall-derived oligogalacturonides (OG) are well characterized DAMPs that elicit plant immune responses such as MAPK activation, [Ca2+]cyt variations, H2O2 production, defense-related gene expression and enhanced resistance against Botrytis cinerea. Our study focused on a new polysaccharide component of the plant cell wall called xyloglucans (Xh) and compared the immune events triggered by OG and Xh in Arabidopsis thaliana. Our results indicated that Xh can be considered as new elicitors as they induced MAPK activation, the expression of defense-related genes, callose deposition and triggered immunity against Botrytis cinerea. By using a genetic approach, our data indicated that the Xh-triggered immunity against B. cinerea requires the phytoalexin and jasmonic aciddependent pathways

Exploration clinique et biologique du NO

En 1980, Furchgott et al. démontrent que la relaxation des cellules musculaires lisses artérielles en réponse à l’acétylcholine est dépendante de l’intégrité anatomique de l’endothélium. Ils baptisent le principe à l’origine de cette relation intercellulaire EDRF (Endothelium Derived Relaxing Factor), qui fut identifié 7 ans plus tard comme étant le monoxyde d’azote (NO), un gaz radicalaire. Au niveau des vaisseaux, le NO produit localement est généré par la NO synthase endothéliale et a une action essentiellement paracrine (relaxation des cellules musculaires lisses sous- jacentes, mais aussi l’inhibition de l’agrégation plaquettaire). La demi-vie du NO est brève in vivo, et son étude est donc difficile. On dispose actuellement de techniques invasives et non invasives qui permettent d’explorer les variations de calibre ou de débit artériels. L’observation princeps de Furchgott préfigure de façon magistrale toute la physiopathologie de la fonction relaxante de l’endothélium. En effet, de nombreuses affections, et en particulier l’athérosclérose, s’accompagnent d'anomalies de la vasodilatation endothélium-dépendante (« dysfonction endothéliale »). Tandis que l’acétylcholine (ou la sérotonine) injectée dans une artère saine entraîne une vasodilatation, elle provoque en revanche une vasoconstriction dans une artère athéroscléreuse, du fait d’une diminution de la biodisponibité du NO. Ce déficit de NO pourrait précipiter la maladie coronaire en favorisant, outre le spasme artériel, l'interaction entre les plaquettes et la paroi artérielle et donc la thrombose. En clinique, le NO ne peut pas être mesuré directement, à l’exception du NO détecté dans l’air exhalé. In vivo, le NO est rapidement oxydé en nitrite ([math]) et en nitrate ([math]), l’ensemble étant appelé NOx. Nous détaillons ici les limites de ce dosage comme index biochimique de la production de NO d’origine « endothéliale »

UTILISATION D'OLIGOMÈRES D'ALGINATES POUR AMÉLIORER LA PROTECTION DES PLANTES CONTRE LES PATHOGÈNES

The invention concerns the use of alginate oligomers in sequence α(1-4)Guluronane and/or ß(1-4)Mannuronane having a DP greater than 30, as an active ingredient of biocontrol products in plants, and that may be combined with another molecules such as phytohormones, against cryptogamic diseases of plants, in particular of vine (Vitis vinifera), or to protect other species against aggressors such as pathogenic microbes or insects.L'invention concerne l'utilisation d'oligomères d'alginate dans la séquence α(1-4)Guluronane et/ou ß(1-4)Mannuronane ayant un DP supérieur à 30, en tant que principe actif de produits de lutte biologique dans des plantes, et qui peuvent être combinées avec d'autres molécules telles que des phytohormones, contre des maladies cryptogamiques de plantes, en particulier de la vigne (Vitis vinifera), ou pour protéger d'autres espèces contre des agressions telles que des microbes pathogènes ou des insectes

The xyloglucans : are they new elicitors of Arabidopsis thaliana immunity?

Highlights • Fragments derived from plant cell wall xyloglucans induce Arabidopsis thaliana defence responses and protection against Botrytis cinerea • Xyloglucan-triggered immunity against B. cinerea requires the phytoalexin, ethylene and jasmonic acid-dependent pathways Results and discussion Xh treatment induced a dose-dependent MAPK phosphorylation in Arabidopsis cell suspensions. From 5 to 60 min, Xh treatment induced a rapid phosphorylation of two MAPKs with relative molecular masses of 43 and 47 kDa. Treatment with Xh did not induce any free [Ca2+]cyt variations whereas OG treatment induced a rapid and transient increase in free [Ca2+]cyt that peaked after 30 sec. Xh did not trigger any H2O2 production, as observed in control cells but OG treatment induced an oxidative burst with maximal H2O2 production detected at 10 min. To investigate late defence responses, we analysed callose deposition at the site of infection by B. cinerea after elicitor treatments. Xh and OG-treatment resulted in a significant increase of callose production 3 days post infection with the pathogen. The expression of different defence genes was analysed by qPCR. Xh triggered the accumulation of PR-1, PAD3, LOX3 and ICS1 transcripts. To further investigate the efficacy of xyloglucans to induce resistance, we performed protection assays against the necrotrophic fungi B. cinerea and the biotrophic oomycete H. arabidopsidis. Xh treatment applied 48 h before pathogen infection significantly reduced both the B. cinerea lesion diameter and the H. arabidopsidis sporulation on Arabidopsis leaves. Together, these results suggest that Xh are new elicitors of Arabidopsis immunity. Interestingly, some defence responses triggered by Xh are different from those induced by OG. As Arabidopsis responds to Xh treatment, we aimed to identify some signalling components. By using a genetic approach with T-DNA mutants in different defence responses, our data indicated that the Xh-triggered immunity against B. cinerea requires the phytoalexin (cyp71A13, pad3, pad2), ethylene (etr1, ein2) and jasmonic acid-dependent pathways (dde2, lox3, coi1).These results show that Xh are recognised by Arabidopsis. In order to identify a receptor involved in Xh perception or signalling, knock-out mutants of previously known A. thaliana receptors or candidate receptors up-regulated in microarray analysis have been

Increasing vineyard sustainability: innovating a targeted chitosan-derived biocontrol solution to induce grapevine resistance against downy and powdery mildews

The European Green Deal aims to reduce the pesticide use, notably by developing biocontrol products to protect crops from diseases. Indeed, the use of significant amounts of chemicals negatively impact the environment such as soil microbial biodiversity or groundwater quality, and human health. Grapevine (Vitis vinifera) was selected as one of the first targeted crop due to its economic importance and its dependence on fungicides to control the main damaging diseases worldwide: grey mold, downy and powdery mildews. Chitosan, a biopolymer extracted from crustacean exoskeletons, has been used as a biocontrol agent in many plant species, including grapevine, against a variety of cryptogamic diseases such as downy mildew (Plasmopara viticola), powdery mildew (Erysiphe necator) and grey mold (Botrytis cinerea). However, the precise molecular mechanisms underlying its mode of action remain unclear: is it a direct biopesticide effect or an indirect elicitation activity, or both? In this study, we investigated six chitosans with diverse degrees of polymerization (DP) ranging from low to high DP (12, 25, 33, 44, 100, and 470). We scrutinized their biological activities by evaluating both their antifungal properties and their abilities to induce grapevine immune responses. To investigate their elicitor activity, we analyzed their ability to induce MAPKs phosphorylation, the activation of defense genes and metabolite changes in grapevine. Our results indicate that the chitosans with a low DP are more effective in inducing grapevine defenses and possess the strongest biopesticide effect against B. cinerea and P. viticola. We identified chitosan with DP12 as the most efficient resistance inducer. Then, chitosan DP12 has been tested against downy and powdery mildews in the vineyard trials performed during the last three years. Results obtained indicated that a chitosan-based biocontrol product could be sufficiently efficient when the amount of pathogen inoculum is quite low and could be combined with only two fungicide treatments during whole season programs to obtain a good protection efficiency. On the whole, a chitosan-based biocontrol product could become an interesting alternative to meet the chemicals reduction targeted in sustainable viticulture

Antiadhesive properties of glycoclusters against Pseudomonas aeruginosa lung infection

Pseudomonas aeruginosa lung infections are a major cause of death in cystic fibrosis and hospitalized patients. Treating these infections is becoming difficult due to the emergence of conventional antimicrobial multiresistance. While monosaccharides have proved beneficial against such bacterial lung infection, the design of several multivalent glycosylated macromolecules has been shown to be also beneficial on biofilm dispersion. In this study, calix[4]arene-based glycoclusters functionalized with galactosides or fucosides have been synthesized. The characterization of their inhibitory properties on Pseudomonas aeruginosa aggregation, biofilm formation, adhesion on epithelial cells, and destruction of alveolar tissues were performed. The antiadhesive properties of the designed glycoclusters were demonstrated through several in vitro bioassays. An in vivo mouse model of lung infection provided an almost complete protection against Pseudomonas aeruginosa with the designed glycoclusters