Fig. 5.

Microtubular and nuclear organization and dynamics visualized by confocal and bright-field microscopy. (A) Two adjacent optical sections (0.5 μm apart) of a heterokaryotic conidium and germ tube showing five nuclei (n) after labeling with H1-GFP and β-tubulin-GFP, visualized by confocal microscopy. These two optical sections were selected from a continuous z stack of 20 optical sections captured in 0.5-μm steps. Arrows indicate the locations of spindle pole bodies with associated microtubules. Nuclei appear to be linked via microtubules. A large vacuole (v) seems to have pushed two of the nuclei to the periphery of the conidium. C, conidium; GT, germ tube. Bar, 5 μm. (B) Lack of inhibition of CAT fusion and homing by treatment with the microtubule-depolymerizing drug benomyl (40 μg ml⁻¹). Two hours after treatment, the microtubules were reduced to punctate spots. Bar, 10 μm. (C) Nuclei labeled with H1-GFP migrate through fused CATs visualized by combined confocal and bright-field microscopy. (D) Benomyl treatment prevents the formation of long germ tubes. An H1-GFP-labeled strain was incubated with benomyl (35 μg ml⁻¹) for 6 h visualized by combined wide-field fluorescence and differential interference contrast (DIC) microscopy. Small buds (arrow) may represent the initiation of germ tube formation, but these buds did not elongate further. Bar, 5 μm.