Endosomal transport of septin mRNAs and encoded proteins in the phytopathogen Ustilago maydis
Final Report Abstract
Ustilago maydis is a phytopathogenic fungus that switches form yeast to hyphal growth during infection. Important for efficient hyphal growth is endosomal mRNA transport along microtubules mediated by the action of kinesin and cytoplasmic dynein. The key RNA-binding protein is Rrm4. Initially, the mRNA encoding the septin Cdc3 was identified as important cargo mRNA. Septins are cytoskeletal elements that form defined hetero-octameric subcomplexes consisting of four septins Cdc3, Cdc10, Cdc11 and Cdc12. These assemble into higher-order structures. We observed that also the translation product Cdc3 localises to transport endosomes and forms defined filaments with a gradient emerging from the growing hyphal tip. Interestingly, mRNA and protein localisation of the septin Cdc3 was dependent of Rrm4. Thus, we hypothesised that local translation of septin mRNA on the cytoplasmic surface of transport endosomes is important for the correct subcellular localisation. In this project, we studied the assembly of all four septins and aimed to establish a system to study local translation in vivo. We discovered that the mRNAs of all four septins are transported Rrm4-dependently on transport endosomes. Their localisation in endosomes was dependent on each other suggesting that heteromeric complexes are assembled on endosomes that transport the septins to form filaments a the growth pole. For the establishment of the in vivo translation system we succeeded in establishing an improved red fluorescent protein for U. maydis, we expressed a single-chain antibody recognising its epitope in vivo and established the 2A peptide technology to express polycistronic mRNAs. The last step in establishing a protein degradation tag was not finished due to time reasons, so that unfortunately the final system could not be established. Nevertheless, we demonstrated compelling evidence for the in vivo assembly of septins on transport endosomes and improved the molecular tool box in U. maydis substantially.
Publications
- (2016) Endosomal assembly and transport of heteromeric septin complexes promote septin cytoskeleton formation. J. Cell Sci. 129: 2778-2792
S. Zander, S. Baumann, S. Weidtkamp-Peters and M. Feldbrügge
(See online at https://doi.org/10.1242/jcs.182824) - (2018) mRNA transport in fungal top models. WIREs RNA. 9: e1453
D. Niessing, R.P. Jansen, T. Pohlmann and M. Feldbrügge
(See online at https://doi.org/10.1002/wrna.1453) - (2018) RNA live imaging in the model microorganism Ustilago maydis. Methods in Mol. Biol. RNA detection, ed. I. Gaspar, Humana Press, New York, 1649: 319-335
S. Zander, K. Müntjes and M. Feldbrügge
(See online at https://doi.org/10.1007/978-1-4939-7213-5_21) - (2019) Membrane-associated RNA- binding proteins orchestrate organelle-coupled translation. Trends Cell Biol. 29: 178-188
J. Béthune, R.-P. Jansen, M. Feldbrügge and K. Zarnack
(See online at https://doi.org/10.1016/j.tcb.2018.10.005) - (2019) The multi PAM2 protein Upa2 functions as novel core component of endosomal mRNA transport. EMBO Rep. 24: e47381
S. Jankowski, T. Pohlmann, S. Baumann, K. Müntjes, S.K. Devan, S. Zander and M. Feldbrügge
(See online at https://doi.org/10.15252/embr.201847381) - (2020) Polycistronic gene expression in the model microorganism Ustilago maydis. Front. Microbiol. 11:1384
K. Müntjes, M. Philipp, L. Hüsemann, N. Heucken, S. Weidtkamp-Peters, K. Schipper, M. Zurbriggen, M. Feldbrügge
(See online at https://doi.org/10.1101/2020.05.06.081414) - (2020) The STRIPAK signaling complex regulates dephosphorylation of GUL1, an RNA-binding protein that shuttles on endosomes. PLoS Genet. 16: e1008819
V. Stein, B. Blank-Landeshammer, K. Müntjes, R. Märker, I. Teichert, M. Feldbrügge, A. Sickmann, and U. Kück
(See online at https://doi.org/10.1101/2020.05.01.072009)
