Macroconidial defect in ΔFghtf1 mutant.

(A) Budding pattern of macroconidial development in F. graminearum. Wild-type PH-1 strain produced incipient macroconidium without distinct septation directly from hyphae. ΔFghtf1 deletion mutant produced matured conidium with clear septation from the tip of hyphae. The resulting cells were observed with a DIC microscope and also stained with DAPI and calcofluor white (CFW) to visualize nuclei and septa, respectively, under a fluorescence microscope. Black arrows in PH-1 strain indicated the position of cell division. s, septa, n, nucleus. Bar = 20 µm. (B) Macroconidia matured and then released from the hyphae by mechanical force during incubation with agitation. ΔFghtf1 mutant was stained with calcofluor white (CFW) to visualize cell wall and septa. White arrows indicate the point of breakage. Bar = 20 µm. (C) Morphological phenotypes of macroconidia produced by PH-1 and ΔFghtf1 mutant. a, PH-1, typical Fusarium macroconidium, the apical cell is in the below (black arrow), and the foot cell is on the top (white arrows). b–d, ΔFghtf1 mutant, an obvious defect in foot cell. Bar = 20 µm.