The role of microtubule-dependent mRNA transport during polar growth of Ustilago maydis

玉米黑穗病菌引起玉米黑穗病。最近，我们证明了rna结合蛋白与致病性有关。特别是，rrm4的缺失导致丝的形成受损和毒力降低。该基因编码一个rnabin结合蛋白，其结构域结构新颖，包含三个n端RNA识别动机（RRMs）和一个C端PABC结构域（聚(a)结合蛋白C端），称为蛋白质相互作用界面。Rrm4结构域的突变分析表明，n端串联Rrm4极有可能构成rna结合结构域。通过紫外交联实验，在体内证实了Rrm4的RNA结合活性。融合绿色荧光蛋白（eGfp）的Rrm4的亚细胞定位表明，Rrm4-eGfp被组装成沿微管穿梭的颗粒，颗粒的形成依赖于PABC结构域。因此，我们假设含有rrm4的核糖核蛋白（RNP）颗粒参与了依赖于微管的RNA转运，这一过程对感染丝的极性生长很重要。在这个提议中，我们想要确定分子货物和包括分子马达在内的运输颗粒的组成。揭示细胞因子的功能将加深我们对RNP颗粒介导的长距离转运的理解，并为涉及微生物致病性的细胞过程提供新的见解。

Ustilago maydis causes smut disease on corn. Recently, we demonstrated that RNAbinding proteins are implicated in pathogenicity. In particular, deletion of rrm4 led to impaired filament formation and reduced virulence. This gene encodes a RNAbinding protein with a novel domain architecture containing three N-terminal RNA recognition motives (RRMs) in combination with a C-terminal PABC domain (Poly (A)-binding protein C terminus) known as protein interaction interface. Mutational analysis of Rrm4 domains revealed that the N-terminal tandem RRMs most likely constitute the RNA-binding domain. The RNA binding activity of Rrm4 was confirmed in vivo performing UV cross-linking experiments. Subcellular localisation of Rrm4 fused to the green fluorescent protein (eGfp) showed that Rrm4-eGfp is assembled into particles that shuttle along microtubules and that particle formation depends on the PABC domain. Thus, we hypothesize that Rrm4-containing ribonucleoprotein (RNP) particles participate in microtubule-dependent RNA transport, a process that is important for polar growth of the infectious filament. In this proposal we want to identify the molecular cargo and the composition of transport particles including molecular motors. Unravelling the function of the cellular factors will deepen our understanding on long distance transport mediated by RNP particles as well as provide novel insights into cellular processes involved in pathogenicity of microorganisms.