GUS (glucuronidase)-expressing U. hordei proliferating during a compatible interaction in a barley influorescence (floral meristem). Note that very little fungal biomass can be observed in the rest of the tissue. Upon penetration of the seedling and subsequent infection, the fungus establishes itself in the meristem. Increase in fungal biomass can be observed once the meristem differentiates to become an inflorescence. Obviously, the fungus must perceive and cue into several as yet unknown plant signals!