Cellular function of the SPB proteins Cnm67 and Spc72 in Saccaromyces cerevisiae and the filamentous fungus Ashbya gossypii.
Claudia Birrer, Tineke van den Hoorn, Peter Philippsen, Dominic Hoepfner
Applied Microbiology, Biozentrum, University Basel, Klingelbergstr. 50, Basel, 4056, Switzerland
S. cerevisiae and A. gossypii are closely related based on their fully sequenced and annotated genomes. Despite the very similar sets of genes, the morphogenesis of both organisms is very different. In contrast to the small, mononucleate S. cerevisiae cells, A. gossypii grows as long and branched hyphae carrying many nuclei in the same cytoplasm. To investigate the influence of the tubulin cytoskeleton on nuclear distribution in these multinucleated hyphae, we deleted two genes, AgSPC72 and AgCNM67, which in S. cerevisiae are both part of the spindle pole body outer plaque, organizing cytoplasmic microtubules. As in S. cerevisiae, both deletions are viable. Deletion of AgCNM67 results in a slow-growth phenotype but shows no obvious changes of the nuclear distribution. We also observed that the mutant strain is not able to sporulate. Hyphae lacking AgSPC72 have a slightly decreased growth speed compared to wildtype, but spores can still be formed. The nuclear distribution is disturbed even though, and contrary to the spc72 deletion mutant in S. cerevisiae, long astral microtubules are still present. This raises the question about the differences in the organization of astral microtubules in A. gossypii and S. cerevisiae. We have begun to investigate this question by monitoring the GFP-labeled network of microtubules in A. gossypii.