GALAPAGOS

Pectins are a family of highly complex cell wall polysaccharides which play a major role in controlling plant vegetative and reproductive development. They are widely used in the food ingredient sector (i.e. as gelating agent/stabilizers or hydrogels for drug delivery). The simplest and the most abundant pectic block is homogalacturonan (HG), an unbranched polymer of alpha-(1-4) linked D galacturonic acids residues that can be methylesterified at the C6 position. This determines the degree of methylesterification (DM), which is controlled in the cell wall by the large multigenic family of pectin methylesterases (PMEs, 66 isoforms) and determines the susceptibility of HG to degradation by specific enzymes to produce oligogalacturonides (OGs). The properties of HG-derived OGs are related to their i) Degree of Polymerisation, ii) Degree of Methylesterification, and iii) pattern of methylesterification. In planta, oligogalacturonids are notably involved in eliciting plant defense responses against bacterial and fungal pathogens as well as aphids, a property that can be used to engineer dedicated biomass-derived products for plant protection. This approach requires a better knowledge of the structure, the specificity and the mode of action of OGs. This aspect is of importance in the current context of the reduction of chemicals used in phytoprotection (Grenelle de l’Environnement, EcoPhyto-2018). Based on preliminary results showing the relations between the structure of OGs and their biological activity, and using the biochemical specificity of PME enzymes, the project will provide a means by which we will be able to create specific methylester decoration on HG. Using this tool, the project will generate purified OGs of characterized degree of polymerization (DP) and degree/pattern of methylesterification. This will allow the precise structure/properties analysis of these OGs to be determined. In particular, to address the functionality and potential application of the generated OGs, their properties will be tested with regards to: i) responses of plants to bacterial and fungal pathogens and ii) effects on plant growth. The first aspect will notably concerns both model plant (Arabidopsis) and species of agro-economical interest (grape and potato). As an additional outcome, through an external collaboration, the potential prebiotic activity of these compounds will be tested. Altogether, the project will provide an integrated multidisciplinary approach relating the fine structure of pectic oligomers to their potential application. The project brings together three partners (Univ. Amiens, INRA Nantes, Univ./INRA Dijon) with highly complementary expertise, and external collaborator (Univ. Reading). The project fits into the field of three competitivity clusters (Industrie Agro-Ressources, Végépolys and VITAGORA) and has potential application as shown by letters of support (Cargill, Comité Nord, BIVB).