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

长期以来，细胞细胞器如过氧化物体、内质网(ER)和内小体一直被认为是具有不同隔离功能的受限空间。过氧化物酶体参与初级和次级代谢以及活性氧(ROS)信号传递，而内体则是大分子长距离运输的多用途平台。然而，最近的进展表明，细胞器是非常动态的结构，彼此之间相互作用很强。例如，在真菌细胞中，通过显示早期内体的微管依赖的运输将过氧化体分布在整个菌丝中，在过氧化体和内体之间建立了密切的分子联系。此外，脂滴(LDS)和内质网片段是由这些内体运输的。同时，LDS、内小体和过氧体的形成和动态依赖于内质网。值得注意的是，编码间隔蛋白的mRNAs是早期内体的额外重要货物。实验数据支持一个模型，在该模型中，Septin mRNAs在内体细胞质表面的局部翻译促进了Septin低聚体的组装和高阶结构的形成。在这里，我们建议研究(I)过氧化体在极地生长和发育过程中的生物学功能，(Ii)mRNA转运与过氧化体、内质网和内体之间的串扰之间的潜在功能联系。为了提供对这些方面的广泛看法，我们的团队由真菌生物学专家组成，他们使用了已建立的模型系统，如黑曲霉、黑曲霉、粗糙脉孢霉和鹅膏霉菌。遗传学、生物化学和细胞生物学方法将被结合起来，以确定细胞器动力学中的分子机制和基本成分。通过比较不同真菌模型中细胞器之间的串扰，我们将揭示基本的进化保守过程，以及适应不同真菌生活方式的特定机制。所获得的结果将引起细胞生物学家的普遍兴趣，所获得的知识可用于改进次生代谢物的生产和开发新型杀菌剂。

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.