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

玉米黑粉菌引起玉米黑穗病。最近，我们证明了RNA结合蛋白与致病性有关。特别是，rrm 4的缺失导致受损的细丝形成和降低的毒力。该基因编码的RNA结合蛋白具有一种新的结构域结构，该结构域包含三个N-末端RNA识别基序（RRM）和一个称为蛋白质相互作用界面的C-末端PABC结构域（Poly（A）-binding protein C terminal）。Rrm 4结构域的突变分析显示，N-末端串联RRM最有可能构成RNA结合结构域。Rrm 4的RNA结合活性在体内进行UV交联实验证实。融合到绿色荧光蛋白（eGfp）的Rrm 4的亚细胞定位显示，Rrm 4-eGfp组装成沿着沿着微管穿梭的颗粒，并且颗粒形成取决于PABC结构域。因此，我们假设，Rrm 4含有核糖核蛋白（RNP）颗粒参与微管依赖的RNA运输，这是一个重要的极性增长的感染性丝的过程。在这个提议中，我们希望确定分子货物和运输粒子的组成，包括分子马达。揭示细胞因子的功能将加深我们对RNP颗粒介导的长距离运输的理解，并为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.