Updated project metadata. Botrytis cinerea is the causing agent of grey mould on hundreds of plants cultivated in fields, tunnels and greenhouses worldwide, including economically important crops. Considering the central role of the fungal cell wall in the interaction between fungi and plants, the role of a conserved putative polysaccharide synthase in the physiology, development and virulence of B. cinerea was explored. To this aim, the BcCps1 gene was deleted and the mutant strain was characterized. In order to reveal the impact of the mutation on the fungal secretion, the exo-proteome of the wild type and mutant strains were prepared for comparative analysis of their contents.