Phytophthora infestans effector PexRD54 associates with host Rab GTPase Rab8-1 to reprogram endomembrane transport

丝状真菌是一组包括卵菌属疫霉属、锈菌属和白粉病属在内的真核生物病原体，它们引起最具破坏性的植物病害并威胁全球粮食安全。这些病原体每年给现代农业造成数十亿美元的损失，并严重影响发展中国家的自给农业。这些微生物通过专门的细胞结构被容纳在宿主细胞内。然而，对植物细胞内微生物适应性的分子机制知之甚少。拟议的研究的目的是表征宿主过程中所需的住宿丝状植物病原体在植物细胞内的具体重点是说明植物内膜运输系统在这一过程中的作用。在卵菌中，疫霉属（Phytophthora spp.）在世界上，这些病毒会导致一些最具破坏性的植物疾病，并对马铃薯、番茄和大豆等重要作物物种造成巨大的经济损失，以及对自然生态系统的环境破坏。致病疫霉（Phytophthora infestans）是爱尔兰马铃薯饥荒病原体，其引起马铃薯和番茄的晚疫病，是对全球粮食生产的最重要的生物威胁之一，导致每年超过50亿美元的全球经济损失。不幸的是，马铃薯晚疫病是一种重新出现的破坏性疾病，最近在英国各地的马铃薯农场造成了严重的流行。我们的长期目标是剖析植物细胞自主免疫的分子机制和内膜交通在这一过程中的作用，特别是使用致病疫霉作为模式病原体。与其他一些形成破坏性植物病害的丝状病原体一样，致病疫霉通过形成称为吸器的特化隔室而被容纳在宿主细胞内，吸器通过新合成的来源和组成未知的宿主衍生膜与入侵的植物细胞分离。该界面通过实现有效的大分子交换对于寄生虫感染的发展至关重要。因此，了解寄主-病原体界面大分子交换过程的调控对开发植物抗病性工程新策略至关重要。不幸的是，尽管早在几十年前就被发现了，但我们目前对吸器的了解仍然有限。在这个界面上破译细胞和生化活动是理解发病机制的关键。与其他病原体一样，致病疫霉分泌一系列蛋白质，称为抑制植物免疫并使寄生虫感染成为可能的效应物。最近，我们发现这些效应物中的一些特异性地积累在受感染的植物细胞内的宿主病原体界面处。在这项研究中，我们的目的是确定主机组件的局灶性免疫使用这样的效应，称为PexRD 54，作为分子探针。我们的初步工作揭示了在吸器周围，PexRD 54与真核小泡运输调节因子Rab GTPases家族成员Rab 8 -1的宿主蛋白相关。我们的目标是对PexRD 54和Rab 8 -1进行功能表征，以确定这些分子在宿主病原体界面中的作用。本研究将有助于建立病原菌干扰的植物内膜运输过程的功能表征，并有助于了解宿主病原菌界面的起源，功能和组成。反过来，PexRD 54操纵Rab 8 -1的详细知识将提高我们对植物细胞内微生物适应性的理解，并将为作物的工程抗病性创造新的机会。

Filamentous plant pathogens are a group of eukaryotic pathogens including oomycete genus Phytophthora, as well as rust fungi, and Powdery mildew fungi, which cause most destructive plant diseases and threaten global food security. These pathogens cost billions of dollars annual looses to modern agriculture and severely impact subsistence agriculture in developing countries. These microorganisms are accommodated within the host cells through specialized cellular structures. However, little is known about molecular mechanisms underlying microbial accommodation inside the plant cells. The proposed research aims to characterize the host processes required for accommodation of filamentous plant pathogens inside the plant cells with a specific focus on illustrating the role of plant endomembrane transport system in this process. Among the oomycetes, Phytophthora spp. cause some of the most destructive plant diseases in the world and cause enormous economic damage to important crop species such as potato, tomato, and soybean, as well as environmental damage in natural ecosystems. Phytophthora infestans, the Irish potato famine pathogen, which causes late blight of potato and tomato, is one of the most important biotic threats to global food production leading to worldwide economic losses exceeding $5 billion annually. Unfortunately, late blight of potato is a reemerging destructive disease, which caused severe epidemics in potato farms across the UK lately. Our long-term objective is to dissect the molecular mechanisms underlying plant cell autonomous immunity and the role of endomembrane traffic in this process by particularly using P. infestans as a model pathogen. Like some other filamentous pathogens that form destructive plant diseases, P. infestans is accommodated inside the host cells by forming specialized compartments termed haustoria, which are separated from the invaded plant cells by newly synthesized host derived membranes with unknown origin and composition. This interface is critical for development of parasitic infection by enabling efficient macromolecule exchange. Therefore, understanding the regulation of macromolecule exchange processes at host pathogen interface is critical to develop novel strategies to engineer disease resistance in plants. Unfortunately, despite being discovered decades ago, our current knowledge about haustoria is limited. Deciphering the cellular and biochemical activities at this interface is critical for understanding the mechanisms of pathogenesis. Like other pathogens, P. infestans secretes a battery of proteins, termed effectors that suppress plant immunity and enable parasitic infection. Recently we discovered that some of these effectors specifically accumulate at the host pathogen interface inside the infected plant cells. In this study we aimed to identify host components of focal immunity using one such effector, termed PexRD54, as a molecular probe. Our preliminary work unraveled that around haustoria, PexRD54 associated with a host protein named Rab8-1, a member of Rab GTPases family of eukaryotic vesicle trafficking regulators. Our goal is to functionally characterize PexRD54 and Rab8-1 in order to establish the roles of these molecules at host pathogen interface. This study will help to establish functional characterization of plant endomembrane transport processes perturbed by pathogens and help understanding the origin, function and composition of the host pathogen interface. In turn, a detailed knowledge of PexRD54 manipulation of Rab8-1 will improve our understanding of the microbial accommodation inside the plant cells and will allow for creating renewed opportunities for engineering disease resistance in crops.