Analysis of microtubule-organizing centers (MTOCs) in Aspergillus nidulans and Neurospora crassa

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Microtubule formation in eukaryotic cells depends on large, multi-subunit protein complexes, called Microtubule-organizing centres (MTOCs). One extremely well-studied MTOC is the one in Saccharomyces cerevisiae, where the MTOC is embedded into the nuclear envelope and named spindle-pole body (SPB). In Schizosaccharomyces pombe three different MTOCs generate the MT arrays during different stages of the cell cycle, multiple interphase iMTOCs located in the nuclear envelope, the SPBs, and equatorial, eMTOCs, during cyokinesis. All three are spatially and temporally regulated. In the filamentous fungus Aspergillus nidulans, in which gamma-tubulin was discovered, two stable MTOCs were described, the SPBs and septal MTOCs (sMTOCs). We found that sMTOCs are anchored at septa through the disordered protein Spa10, and that the protein composition resembles the one of the outer plaque of SPBs. In Neurospora crassa SPBs polymerize mitotic and cytoplasmic MTs, but in addition there is evidence for MTOCs in the growing tip in the cytoplasm. Nothing is known about the biochemical composition and the activity. Here, we propose to perform a comparative study of the MTOCs in A. nidulans and N. crassa. The role of several proteins, such as MOZART 1 (MztA and MTZ-1) or the J-domain containing protein RspA, will be studied. Besides the biochemical composition of MTOCs, the hierarchy of the assembly will be unraveled. In addition, non-targeted approaches, such as BioID or GFP-trap technology, will be undertaken to discover novel structural and regulatory components.