During filamentous fungus development, multinucleated hyphae employ a system for 
long-range nuclear migration to maintain an equal nuclear density. A decade ago 
the microtubule motor dynein was shown to play a central role in this process. 
Previous studies with Ashbya gossypii revealed extensive bidirectional movements 
and bypassings of nuclei, an autonomous cytoplasmic microtubule (cMT) 
cytoskeleton emanating from each nucleus, and pulling of nuclei by sliding of 
cMTs along the cortex. Here, we show that dynein is the sole motor for 
bidirectional movements and bypassing because these movements are concomitantly 
decreased in mutants carrying truncations of the dynein heavy-chain DYN1 
promoter. The dynactin component Jnm1, the accessory proteins Dyn2 and Ndl1, and 
the potential dynein cortical anchor Num1 are also involved in the dynamic 
distribution of nuclei. In their absence, nuclei aggregate to different degrees, 
whereby the mutants with dense nuclear clusters grow extremely long cMTs. As in 
budding yeast, we found that dynein is delivered to cMT plus ends, and its 
activity or processivity is probably controlled by dynactin and Num1. Together 
with its role in powering nuclear movements, we propose that dynein also plays 
(directly or indirectly) a role in the control of cMT length. Those combined 
dynein actions prevent nuclear clustering in A. gossypii and thus reveal a novel 
cellular role for dynein.