Secreted protein required for appressorial penetration of intact host epidermal cells and for pathogenicity. Secreted exocytosis coupled with SEC22-mediated traffic and accumulates in a ring-like region around the neck of the biotrophic primary hyphae. Expressed in the plant infection stage. Impairs pathogenicity (PubMed:22589729, PubMed:24850852). Leads to clear reduction in lesion development on cucumber leaves (PubMed:22589729). Belongs to the MC69 virulence factor family.