Membrane-coupled mRNA trafficking in Ustilago maydis

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Active transport and local translation of mRNAs are essential to precisely determine spatiotemporal protein expression. Evidence is accumulating that there is an intimate link between mRNA transport and membrane trafficking, including an intensive co-transport of mRNAs with ER or endosomes. The latter was discovered studying microtubule-dependent transport of mRNAs in infectious hyphae of the plant pathogen Ustilago maydis. In particular, transport of septin mRNA and encoded protein on shuttling endosomes is essential for efficient septin filamentation during polar growth. In this project, we will address two key aspects of membrane-coupled mRNA trafficking. Firstly, we aim to identify novel links between mRNA and membrane trafficking during polar growth of infectious hyphae. In close collaboration with partners of the research group we will perform a comparative approach in mammalian cells, Saccharomyces cerevisiae and U. maydis. Our part will be to study the role of newly identified membrane-associated RNA-binding proteins (RBPs) during hyphal growth. We will combine genetic, cell biological and biochemical approaches for functional analysis of these RBPs and uncover the link to membrane trafficking as well as target mRNAs. Secondly, we will identify and study the function of novel components of the endosomal mRNA transport machinery. To this end, we will establish and apply an in vivo proximity-dependent labelling approach in this fungal model organism using the key RBP Rrm4 as bait. In the framework of this research group, we will focus on associated RBPs needed for transport or regulatory factors that, e.g., promote the RNA-binding capacity of Rrm4. Together, the outlined experiments will yield new insight into how membrane trafficking and RNA transport are mechanistically linked. We expect to uncover new cell biological concepts conserved in evolution.