Fig. 4. HET-s(157-289)/GFP forms elongated fibrillar aggregates in vivo upon transition to the prion state. (A) Strains expressing HET-s(157-289)/GFP were analysed by fluorescence microscopy. In the [Het-s*] state, the fluorescence signal is diffuse and cytoplasmic. (B) Upon transition to the [Het-s] prion state, HET-s(157-289) forms fibrillar aggregates. (C) In apical regions, in which septa are absent, fibrillar aggregates grow very large. (D,E) Aggregates are not rigid and are able to bend when blocked by septa. (F) Aggregates are able to pass through an anastomosis bridge. (G) Aggregate extending into an hyphal branch. (H) HET-s(157-289) are incorporated into microconidia. Scale bar, 4 µm.