The grapevine Pectin Methylesterases gene family and its involvement in Botrytis bunch rot control

Plant Pectin Methylesterases (PMEs) represent a group of tissue-specific and developmentally regulated proteins. The gene family is involved in the plant cell wall (CW) remodelling process, by the control of the degree of cell wall pectin methylesterification. Pectin methylesterification also influence the susceptibility to pathogens as Botrytis cinerea (Bc), a necrotrophic fungus responsible of the Botrytis bunch rot in grapevine. In Botrytis, PME as well as other CW degrading enzymes have been identified as virulence factors. To further characterize the PME gene family and its role in the Botrytis bunch rot, the latest genome assembly and annotation were revised and through sequence homology search, a total of 63 PME domain containing proteins were identified, 16 more than a previous identification in grapevine. The in-silico analyses of the family by means of the Vitis gene expression database VESPUCCI as well as Aggregated Gene Co-expression Network approach (AggGCNs) allowed us to identify and enrich gene co-expression modules and build gene co-expression networks. Interestingly, one of the co-expression modules showed a high modulation in presence of Botrytis cinerea infection and particular attention was paid to it. To investigate the contribution of the genes of that module, their expression level in different organs and developmental stages from two grapevine cultivars with divergent Bc susceptibility was investigated. Furthermore, berries were artificially infected with Bc at mature stage to evaluate PME gene expression level and their possible role in the grapevine bunch rot susceptibility. The results obtained contribute to characterize the grapevine PME gene family and the role of specific members in the grapevine-Bc interaction and to select PME genes candidate to the control of Botrytis bunch rot in grapevine.