Biochemical characterization of grape skin cell wall during ripening in relation to Botrytis cinerea susceptibility of two Champagne cultivars

Abstract

Pectins or pectic polysaccharides are one of the major components in grape skin cell wall, they contribute to physiological processes which determine the integrity and rigidity of grape skin tissue. Their composition and organization in the cell wall matrix differ according cultivars and also play an important role in the defense mechanisms against plant pathogen and wounding. During grape ripening, important structural and biochemical changes are modifying the cell wall integrity due to pectolytic enzymes such as pectin methylesterases and polygalacturonases which participate to the cell wall weakening and increase the grape susceptibility to pathogens such as Botrytis cinerea.This work investigated the distribution of pectic polysaccharides in the cell wall according to their molecular weight and the localization of pectins (homogalacturonans) highly and low methyl-esterified in grape skin tissue throughout the berry development of the two main Champagne cultivars (Vitis vinifera cv. Pinot noir and Chardonnay), in relation with in vitro Botrytis cinerea susceptibility tests. The skin cell wall composition was evaluated by size exclusion chromatography (SEC) and the pectin localization by immunogold labelling.The comparative study between the two main grape cultivars from Champagne region highlights differences in pectin composition, Chardonnay skins are characterized by less pectic polysaccharides of high molecular weight (HMW) related to a lower susceptibility to Botrytis cinerea. The pectins cellular localization showed that pectins highly methyl-esterified are more important in Pinot noir cell walls than Chardonnay ones, suggesting different mechanisms of cell walls degradation between Chardonnay and Pinot noir skins.