Crosstalk between peroxisomes, endoplasmic reticulum and endosomes during polar growth and development in fungi

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Cell organelles like peroxisomes, the endoplasmic reticulum (ER) and endosomes have long been considered as confined compartments with distinct isolated functions. Peroxisomes participate in primary and secondary metabolism as well as in Reactive Oxygen Species (ROS) signaling, whereas endosomes serve as multipurpose platforms for long distance transport of macromolecules. However, recent advances show that organelles are rather dynamic structures that heavily interact with each other. For example, a close molecular link between peroxisomes and endosomes was established in fungal cells by showing that microtubule-dependent transport of early endosomes distributes peroxisomes throughout hyphae. In addition, lipid droplets (LDs) and ER segments are transported by these endosomes. At the same time, the formation and dynamics of LDs, endosomes, and peroxisomes depend on the ER. Remarkably, mRNAs encoding septins are an additional important cargo for early endosomes. Experimental data support a model in which local translation of septin mRNAs at the cytoplasmic surface of endosomes promotes septin oligomer assembly and formation of higher-order structures. Here, we propose to investigate (i) the biological function of peroxisomes during polar growth and development, (ii) a potential functional link between mRNA transport and the crosstalk of peroxisomes, ER and endosomes. To provide a broad view on these aspects our team consists of fungal biology experts using established model systems such as Ustilago maydis, Aspergillus nidulans, Neurospora crassa and Podospora anserina. Genetic, biochemical and cell biological approaches will be combined to identify molecular mechanisms and essential components in organelle dynamics. By comparing the crosstalk between organelles in different fungal models, we will uncover fundamental, evolutionary conserved processes, as well as specific mechanisms adapted to the life styles of different fungi. Obtained results will be of general interest for cell biologists and the gained knowledge can be applied to improve the production of secondary metabolites and to develop novel fungicides.