Identification of the grapevine pectin methylesterases and characterization of their role in Botrytis bunch rot

Plant Pectin Methylesterases (PMEs) are tissue-specific and developmentally regulated proteins, encoded by a large gene family. PMEs are involved in plant Cell Wall (CW) remodelling by modifying the degree of pectin methyl esterification and therefore affecting the properties of the CW matrix. Pectin methylesterification impacts on fruit susceptibility to pathogens as Botrytis cinerea (Bc), a necrotrophic fungus, which in grapevine causes Botrytis bunch rot. A sequence homology search using the recent revision of the Vitis vinifera genome assembly and the new annotation available allowed us to identify 63 putative V. vinifera PME (VvPME) isoforms, 16 more than those previously reported. Co-expression analysis of the VvPME genes, performed using the in-house developed Vitis gene expression database VESPUCCI, identified six different co-expression modules. Interestingly, two of them showed very similar modulation upon pathogen infection and one of them included eight VvPME genes co-expressed and modulated in response to Bc infection. To assess the contribution of the basal expression of the selected VvPME genes on Bc susceptibility, we are firstly investigating their expression profiles in a panel of organs from grapevine genotypes with different levels of susceptibility to bunch rot. In a second step, berries of the same genotypes will be artificially inoculated with Bc and analysed both for the expression of the selected genes and for the CW biochemical composition over a time course of the infection. The results obtained in this work will contribute to better understand the role of the VvPME gene family in the grapevine-Bc interaction and represent the basis for the functional characterization of selected VvPME genes in V. vinifera plants and for future breeding applications.