English: Symbiosis of meadow fescue with Epichloë festucae, a heritable symbiont.

Single optical slice confocal micrographs of E. festucae expressing enhanced cyan-fluorescent protein were overlain with DIC bright field images of (A) ovules (bar = 100 µm), (B) embryos (bar = 200 µm), and (C) shoot apical meristem and surrounding new leaves (bar = 200 µm). (D) Asymptomatic (left) and “choked” (right) inflorescences simultaneously produced on a single grass plant infected with a single E. festucae genotype. Vertical (seed) transmission of the symbiont occurs via the asymptomatic inflorescence, whereas the choked inflorescence bears the E. festucae fruiting structure (stroma), which produces sexually derived spores (ascospores) that mediate horizontal transmission.

doi:10.1371/journal.pgen.1003323.g001