Immunofluorescence microscopy of the microtubule cytoskeleton during conjugate division in the dikaryon Pleurotus ostreatus N001.

Fluorescence microscopy was used to describe the distribution of nuclei and the organization of the microtubule network in hyphae of Pleurotus ostreatus. Dikaryotic hyphae of P. ostreatus N001 grow by tip extension with two closely spaced nuclei moving slowly forward with the growing hyphal tip. During vegetative growth of the hyphae, cytoplasmic microtubules are found as long filaments oriented longitudinally within fungal hyphae. When the apical cell reaches a length of approximately 150 μm, the two nuclei divide synchronously. Mitosis occurs in association with clamp connection formation, with one of the nuclei dividing in the hook of the developing clamp connection and the other in the main hypha. After mitosis, two daughter nuclei move forward to approximately the center of the apical cell, while the other two move backward to a central position in the subapical cell. Two septa are formed, one in the clamp and the other across the main axis of the hypha to delimit the apical cell. The use of fluorescence microscopy made it possible to examine the changes in the cytoplasmic microtubules, the configuration of the mitotic apparatus, the site of septation and the post-mitotic nuclear migrations during conjugate division in P. ostreatus dikaryotic hyphae.