ABSTRACT
Centrosomes are important microtubule-organizing centers (MTOCs) in animal cells. In addition, non-centrosomal MTOCs (ncMTOCs) are found in many cell types. Their composition and structure are only poorly understood. Here, we analyzed nuclear MTOCs (spindle-pole bodies, SPBs) and septal MTOCs in Aspergillus nidulans. They both contain γ-tubulin along with members of the family of γ-tubulin complex proteins (GCPs). Our data suggest that SPBs consist of γ-tubulin small complexes (γ-TuSCs) at the outer plaque, and larger γ-tubulin ring complexes (γ-TuRC) at the inner plaque. We show that the MztA protein, an ortholog of the human MOZART protein (also known as MZT1), interacted with the inner plaque receptor PcpA (the homolog of fission yeast Pcp1) at SPBs, while no interaction nor colocalization was detected between MztA and the outer plaque receptor ApsB (fission yeast Mto1). Septal MTOCs consist of γ-TuRCs including MztA but are anchored through AspB and Spa18 (fission yeast Mto2). MztA is not essential for viability, although abnormal spindles were observed frequently in cells lacking MztA. Quantitative PALM imaging revealed unexpected dynamics of the protein composition of SPBs, with changing numbers of γ-tubulin complexes over time during interphase and constant numbers during mitosis.
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Footnotes
Competing interests
The authors declare no competing or financial interests.
Author contributions
Conceptualization: R.F.; Investigation: X.G., M.S., Y.Z., S.F., N.T.; Data curation: X.G.; Writing - original draft: X.G.; Writing - review & editing: R.F.; Supervision: R.F.; Project administration: R.F.; Funding acquisition: R.F.
Funding
This work was supported by the German Science Foundation (Deutsche Forschungsgemeinschaft; DFG), grant number Fi459/20-1, and the Japanese Science and Technology Agency (JST) ERATO (grant number JPMJER1502). X.G. was a fellow of the Chinese Scholarship Council (CSC).
Supplementary information
Supplementary information available online at http://jcs.biologists.org/lookup/doi/10.1242/jcs.234799.supplemental
- Received May 28, 2019.
- Accepted October 28, 2019.
- © 2019. Published by The Company of Biologists Ltd
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