A pectin methylesterase inhibitor GhPMEI58 enhances susceptibility to Botrytis cinerea

Plant cell walls contain large amounts of pectin, whose degree of methylesterification is essential for cell wall integrity and plant resistance to pathogens. PMEIs, which are pectin methylesterase inhibitors, can suppress pectin methylesterases activity and catalyze the demethylesterification of pectin. Thus, PMEIs engage in plant response to fungal pathogens like Botrytis cinerea. However, whether the PMEI genes in Gerbera hybrida respond to B. cinerea remains unknown. In our study, it was demonstrated that GhPMEI58, a pectin methylesterase inhibitory protein isolated from gerbera, acts as an inhibitory regulator of grey mold resistance in Arabidopsis thaliana. The expression level of GhPMEI58 was downregulated after B. cinerea infection in gerbera. Additionally, GhPMEI58 was specifically detected during the vegetative growth stage in transgenic Arabidopsis. Overexpression of GhPMEI58 in Arabidopsis reduced the enzymatic activity of pectin methylesterase in leaves and enhanced susceptibility to B. cinerea. Furthermore, multiple genes linked to plant defense showed obvious expression differences in leaves of transgenic Arabidopsis versus wild type after infection. This study provides a novel insight into how GhPMEI58 modulates plant-pathogen interactions through the methylesterification of cell walls, which offers a promising reverse genetic strategy for breeding superior gerbera cultivars with enhanced resistance to B. cinerea.