Ashbya gossypii has a budding yeast-like genome but grows exclusively as 
multinucleated hyphae. In contrast to budding yeast where positioning of nuclei 
at the bud neck is a major function of cytoplasmic microtubules (cMTs), A. 
gossypii nuclei are constantly in motion and positioning is not an issue. To 
investigate the role of cMTs in nuclear oscillation and bypassing, we 
constructed mutants potentially affecting cMT lengths. Hyphae lacking the plus 
(+)end marker Bik1 or the kinesin Kip2 cannot polymerize long cMTs and lose 
wild-type nuclear movements. Interestingly, hyphae lacking the kinesin Kip3 
display longer cMTs concomitant with increased nuclear oscillation and 
bypassing. Polymerization and depolymerization rates of cMTs are 3 times higher 
in A. gossypii than in budding yeast and cMT catastrophes are rare. Growing cMTs 
slide along the hyphal cortex and exert pulling forces on nuclei. Surprisingly, 
a capture/shrinkage mechanism seems to be absent in A. gossypii. cMTs reaching a 
hyphal tip do not shrink, and cMT +ends accumulate in hyphal tips. Thus, 
differences in cMT dynamics and length control between budding yeast and A. 
gossypii are key elements in the adaptation of the cMT cytoskeleton to much 
longer cells and much higher degrees of nuclear mobilities.