Microtubule-dependent membrane dynamics in Ustilago maydis

Abstract

Long-distance trafficking of membranous structures along the cytoskeleton is crucial for secretion and endocytosis in eukaryotes. Molecular motors are transporting both secretory and endocytic vesicles along polarized microtubules. Here, we review the transport mechanism and biological function of a distinct subset of large vesicles marked by the G-protein Rab5a in the model microorganism Ustilago maydis. These Rab5a-positive endosomes shuttle bi-directionally along microtubules mediated by the Unc104/KIF1A-related motor Kin3 and dynein Dyn1/2. Rab5a-positive endosomes exhibit diverse functions during the life cycle of U. maydis. In haploid budding cells they are involved in cytokinesis and pheromone signaling. During filamentous growth endosomes are used for long-distance transport of mRNA, a prerequisite to maintain polarity most likely via local translation of specific proteins at both the apical and distal ends of filaments. Endosomal co-transport of mRNA constitutes a novel function of these membrane compartments supporting the view that endosomes function as multipurpose platforms.

Keywords: :

• Basidiomycete
• endosomes
• filamentous fungi
• mRNA transport
• microtubules
• pathogen

Disclosure of Potential Conflicts of Interest

There is neither a conflict-of-interest nor a financial interest in publishing this work.

Acknowledgments

We thank lab members for valuable discussion and critical reading of the manuscript. Our research was in part financed by grants from the Deutsche Forschungsgemeinschaft (German Science Foundation) through DFG Fe448/3 and DFG/CONACYT FOR1334. We are grateful to Dr. R. Kahmann from the Max Planck Institute for Terrestrial Microbiology in Marburg for her generous support. We acknowledge the following graduate programs for support: the IMPRS for Environmental, Cellular and Molecular Microbiology (Marburg), the Manchot Graduate School “Molecules of Infection” (Düsseldorf), the CLIB Graduate Cluster Industrial Biotechnology (North Rhine-Westphalia) and the International Graduate School for Plant Science (Düsseldorf, Jülich, Michigan State University).