Plant and fungal Pectin Methylesterase diffusion in pectin gels : a multiscale approach
Résumé
Pectins contribute to plant cell wall mechanical properties and are implied in cell-cell adhesion particularly by the way of establishing pectin-calcium gels. The structure of pectin can be altered by plant or fungi pectin methylesterases (PMEs). PMEs can affect pectin gelling properties by de-esterifying galacturonic acid. Indeed, the increase of free galacturonic acid content in pectin enhances interactions between pectin and calcium ions and then induces a gel reinforcement. PMEs de-esterify pectin in a specific pattern and lead to specific gelling properties according to their origin. In plant cell wall, PMEs de-esterify pectins in the presence of calcium. In this case, de-esterification and gelation occur simultaneously. In this work, the diffusion of two PMEs with either fungal or plant origins and mode of action was characterized with a multi-scale approach in different media consisting in pre-cast or not pectin gels. At microscopic scale, Fluorescence Recovery After Photobleaching (FRAP) and Fluorescent Correlation Spectroscopy (FCS) investigations showed similar diffusion behavior for both enzymes. On the opposite, at macroscopic scale, PMEs diffuse in a different way: the fungal PME diffused faster and in a larger range than the plant PME. According to local and macroscopic diffusion distances, plant and fungal PMEs exhibit different diffusion abilities linked to their specific function in vivo: remodelling cell wall in the vicinity of the cell for plant PME and enhancing plant colonisation for fungal PME [1].