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Sci Adv. 2018 Jan 24;4(1):e1701798. doi: 10.1126/sciadv.1701798. eCollection 2018 Jan.

Superresolution and pulse-chase imaging reveal the role of vesicle transport in polar growth of fungal cells.

Author information

1
Institute of Applied Physics, Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany.
2
Institute of Nanotechnology, KIT, Karlsruhe, Germany.
3
Department of Microbiology, Institute for Applied Biosciences, KIT, Karlsruhe, Germany.
4
Faculty of Biology, University of Athens, Athens, Greece.
5
Institut de Biologie et de Médecine Moléculaires, Université Libre de Bruxelles, Gosselies, Belgium.
6
Department of Physics, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
7
Institute of Toxicology and Genetics, KIT, Eggenstein-Leopoldshafen, Germany.
8
Faculty of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan.

Abstract

Polarized growth of filamentous fungi requires continuous transport of biomolecules to the hyphal tip. To this end, construction materials are packaged in vesicles and transported by motor proteins along microtubules and actin filaments. We have studied these processes with quantitative superresolution localization microscopy of live Aspergillus nidulans cells expressing the photoconvertible protein mEosFPthermo fused to the chitin synthase ChsB. ChsB is mainly located at the Spitzenkörper near the hyphal tip and produces chitin, a key component of the cell wall. We have visualized the pulsatory dynamics of the Spitzenkörper, reflecting vesicle accumulation before exocytosis and their subsequent fusion with the apical plasma membrane. Furthermore, high-speed pulse-chase imaging after photoconversion of mEosFPthermo in a tightly focused spot revealed that ChsB is transported with two different speeds from the cell body to the hyphal tip and vice versa. Comparative analysis using motor protein deletion mutants allowed us to assign the fast movements (7 to 10 μm s-1) to transport of secretory vesicles by kinesin-1, and the slower ones (2 to 7 μm s-1) to transport by kinesin-3 on early endosomes. Our results show how motor proteins ensure the supply of vesicles to the hyphal tip, where temporally regulated exocytosis results in stepwise tip extension.

PMID:
29387789
PMCID:
PMC5787382
DOI:
10.1126/sciadv.1701798
[Indexed for MEDLINE]
Free PMC Article

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