ABSTRACT
Septins are conserved cytoskeletal structures functioning in a variety of biological processes including cytokinesis and cell polarity. A wealth of information exists on the heterooligomeric architecture of septins and their subcellular localization at distinct sites. However, the precise mechanisms of their subcellular assembly and their intracellular transport are unknown. Here, we demonstrate that endosomal transport of septins along microtubules is crucial for formation of higher-order structures in the fungus Ustilago maydis. Importantly, endosomal septin transport is dependent on each individual septin providing strong evidence that septin heteromeric complexes are assembled on endosomes. Furthermore, endosomal trafficking of all four septin mRNAs is required for endosomal localization of their translation products. Based on these results, we propose that local translation promotes the assembly of newly synthesized septins in heteromeric structures on the surface of endosomes. This is important for the long-distance transport of septins and the efficient formation of the septin cytoskeleton.
Footnotes
Author contributions
S.B. and S.Z. were responsible for conception and design, acquisition of data, analysis and interpretation of data, and drafting or revising the article; S.W.-P. was responsible for acquisition of data, and analysis and interpretation of data; M.F. was responsible for conception and design, analysis and interpretation of data, and drafting or revising the article.
Funding
This study was supported by grants from the Deutsche Forschungsgemeinschaft [grant numbers EXC 1028, DFG FE448/9-1 (to M.F.) and CRC1208 (to S.W.P. and M.F.)]; and the iGRAD Molecules of Infection (MOI) programme to S.Z.
