part of formation of structure involved in a symbiotic process appressorium formation initiation of appressorium formation biological_process The process in which a relatively unspecialized cell starts to acquire specialized features of the symbiont appressorium to aid in infection of the host. The host is defined as the larger of the organisms involved in a symbiotic interaction. Note that this term should not be used to annotate gene products of the host. It should only be used to annotate those gene products from the symbiont involved in this process. GO:0075025 initiation of appressorium by symbiont on or near host initiation of symbiont appressorium on or near host initiation of appressorium on or near host appressorium initiation on or near host