Context

The reduction or even stop of usage of synthetic pesticides has become a major challenge in agriculture. However, there’s no single, simple alternative to setup combining production efficiency and economic profitability. This is all the truer for perennial corps such as vines. In an agroecological context, the strategy is to combine various partial-effects levers, including the usage of Plant Defense Stimulator (PDS). The efficiency of PDSs is constant in half-controlled conditions, but is generally variable, or even insufficient for vineyard. So, it’s necessary to get new knowledge about plants immunity and the ways to optimize its stimulation in fields. In this context, our work, which has both fundamental and applied aims, is divided into three main areas:

1. Study of vine immunity
2. Identification of levers permitting to optimize the immune responses of the vine
3. Development of biocontrol in viticulture

Axis 1: Study of vine immunity

During a plant-microorganism interaction, some molecular patterns associated to these microorganisms, the MAMP (Microbe-Associated Molecular Pattern), or released from the vegetal wall during the interaction, the DAMP (Damage-Associated Molecular Pattern), can be recognized by PRR (Pathogen Recognition Receptor) type receptors; which activates the plant’s defenses. Our goal is to study, in the vine, the PRR receptors capable de perceive them. We have identified 16 belonging to the family of LysM-domain receptor kinases (Vitis vinifera LysM-RK or VvLYK) and demonstrated that two are involved in the perception of chitooligosaccharide SDPs such as chitin and chitosan. The goals are:

• To study these VvLYK receptors within the genetic diversity of grapevines and at vine level. Their study in different genotypes will enable us to verify whether the presence of certain natural mutations in the corresponding genes can be correlated with better resistance to disease, and may help guide varietal selection programs aimed at obtaining vines that are more resistant to biotic stresses. Analysis of their spatiotemporal expression (in different organs and at different phenological stages) will also make it possible to target the periods most prone to stimulating plant defenses in the vineyard, in order to develop decision-support tools to make SDPs more effective.
• To understand how grapevines differentiate between pathogenic and beneficial microorganisms to initiate or inhibit an immunity or symbiosis program. A functional genomics approach using CRISPR-Cas9 genome editing is underway to confirm or refute the involvement of certain VvLYK receptors in the initiation or inhibition of defense pathways. The perception of SDP and Myc factors derived from mycorrhizal fungi will be compared in WT and KO CRISPR-Cas9 lines for candidate VvLYKs, and KO vines will be subjected to pathogen infection and in vitro mycorrhization trials.

Moreover, we are trying to understand how this immunity (basal or induced) can be circumvented in the event of vineyard decline (fungal, viral or physiological).

Axis 2: Identification of levers permitting to optimize the immune responses of the vine

Defense disinhibition

In a model species, we showed that the histone deacetylase type-2 (HD2) enzymes are negative regulators of plant immune responses. Based on these results, we have shown that the application of a defense disinhibitor (HD2 inhibitor) prior to the application of an SDP increases the latter's efficacy in protecting grapevines against mildew and powdery mildew. The aim now is to characterize the mode of action of disinhibition (comparison of defense responses induced by an SDP with or without prior disinhibition, identification of genes negatively regulated by HD2) and to validate this strategy in the vineyard, on traditional grape varieties and resistant varieties.

Biostimulation

Biostimulants (BS) are defined as "substances and/or microorganisms whose function [...] is the stimulation of natural processes that promote/improve nutrient uptake or utilization, tolerance to abiotic stresses, or crop quality or yield [...]" (EBIC). So, BS represent agroecological levers of interest.

Unlike fungicides, which act directly on pathogens, SDPs act via the stimulation of plant defenses, which depends on their physiological state, itself impacted by environmental factors (e.g. abiotic stresses). So, BS, via their effects on plant physiology, are likely to modulate SDP-induced defense responses. We have developed an experimental set-up adapted to characterizing the effects of BS on grapevine vitroplants (aerial and root phenotyping, effects on plant physiology) which has enabled us to demonstrate that a BS potentiates the grapevine's response to an SDP and the induction of its resistance to mildew. The aim now is to extend the study to different genotypes and to identify other SBs that are effective on grapevines, in particular those that induce resistance to abiotic stresses (water). More generally, the use of biosolutions (SDP and BS) would enable us to act on the constraints (biotic and abiotic) to which the vine is subjected.

Microbiota/Holobiont

In the vineyard, vines live in association with a diversity of microorganisms (bacteria, fungi and viruses) which modulate their physiology and, consequently, their immunity. This close interaction has led to the definition of the vine holobiont concept. Most of the microorganisms that interact with a plant come from the soil and penetrate the plant through its roots. In conjunction with the "Grapevine health: defenses and mycorrhizae" group, research is therefore focused more specifically on the root compartment. The aim is to study how it functions, in relation to other plant compartments, in contrasting health situations (asymptomatic vs. dying vines) and/or in response to abiotic constraints (particularly hydric), in order to gain a better understanding of its specificity and its ability to mobilize its defenses according to rootstock genotypes, and to identify the repercussions (structural, transcriptomic, metabolic, microbial) associated with the structuring and physiology of the vine holobiont. Plus, this work should make it possible to define bioindicators i- associated with decline, which are intended to be pre-symptomatic and which could facilitate the early diagnosis stages and the identification of relevant and ii- useful action levers for the choice of rootstocks in a context of vineyard renewal, and to identify levers (e.g. use of biosolutions) conditioning or improving the physiology of the root/radicellar system and therefore the plant's adaptive capacity.

Team members :

Permanent members :

Adrian Marielle PR

Aimé Sébastien AI

Blanchard Cécile IE

Bourque Stéphane MCF

Daire Xavier IR

Deulvot Chrystel AI (50%)

Héloir Marie-Claire MCF

Jacquens Lucile IE

Klinguer Agnès AI

Lamotte Olivier (invited searcher)

Leborgne-Castel Nathalie PR

Noirot Elodie IE (25%)

Palavioux Karine TR

Poinssot Benoit PR

Trouvelot Sophie MCF

Truong-Cellier Hoai Nam CR

Contractual :

Brulé Daphnée

Ilbert Chloé

Post-Doctorant

Villette Jérémy

Doctorants

Janotik Adam

Lasterre Laurine

Marzari Tania