The Role of the Cytoskeleton in the Pairing and Positioning of the Two Nuclei in the Apical Cell of the Dikaryon of the Basidiomycete Coprinus cinereus

Abstract

Kamada, T., Hirai, K., and Fujii, M. 1993. The role of the cytoskeleton in the pairing and positioning of the two nuclei in the apical cell of the dikaryon of the basidiomycete Coprinus cinereus. Experimental Mycology 17, 338-344. We examined the effects of tubulin mutations, the anti-microtubule agent benomyl, and the anti-microfilament agents cytochalasin B and E on the pairing and positioning of the two nuclei in the dikaryotic apical cell of the basidiomycete Coprinus cinereus. In the parental wild-type dikaryon, the two nuclei maintain an average separation of 19 μm and an average distance of about 76 μm from the growing hyphal apex; there was a weak tendency that the apex to nucleus distance decreases as cell length decreases. Examination of eight dikaryons homozygous for either one α- or one of seven β-tubulin mutations revealed that all the tubulin mutations disturbed the pairing of the two nuclei without changing the positioning of the leading nucleus. The anti-microtubule agent benomyl disturbed the nuclear pairing without changing the positioning of the leading nucleus. Neither cytochalasin B nor E affected either the pairing or the positioning. These results demonstrate that microtubules participate in the pairing of the two nuclei in the apical cell of the dikaryon and provide evidence against a direct involvement of either microtubules or microfilaments in the mechanism of their positioning relative to the hyphal apex.