Dissecting the journey and functions of barley smut fungus Ustilago hordei immunity-triggering effector UhAvr1 to reveal durable defense strategies in cereals

效应生物学，研究微生物病原体的小分泌蛋白，是人类/动物和植物科学的一个新兴研究领域。研究效应物已经揭示了这些蛋白质与许多基本宿主过程和信号通路相互作用和操纵的方式。效应物靶向发育、蛋白质降解和基因调控，包括防御和抗性反应。因此，效应物告诉我们病原体是如何引起疾病的，但也可以作为探针来阐明基本的生物过程。***基因组测序项目揭示了真菌有大量的效应器，但它们的传递方式、宿主细胞靶点和功能在很大程度上仍然未知。在对几种侵染谷物的担子菌病原菌（大麦黑穗病菌黑穗病菌和相关的小麦叶锈病菌小麦锈病菌）的基因组序列进行生成和分析之后，我们现在可以专注于许多预测效应菌的功能。***我们最近在U. hordei中发现了一种效应物，当感染带有抗性基因Ruh1的大麦品种时，它会触发防御。这种无毒效应物UhAVR1仅在与宿主接触时表达，由真菌分泌，其与Ruh1的相互作用或其作用导致宿主局部细胞死亡并对感染产生免疫。我们将Ruh1基因定位在大麦1号染色体短臂上约200 kb的区域。******该建议旨在阐明三个基本问题：***1。UhAVR1分泌的机制和宿主细胞摄取的决定因素是什么？* * * 2。UhAVR1在大麦细胞中的功能是什么，它是一个真正的毒力因子吗，它针对的是什么宿主细胞过程或蛋白质？* * * 3。UhAVR1如何与Ruh1相互作用并引起免疫，我们能否分离Ruh1？******阐明该模型系统中效应物的传递机制、宿主靶标的识别和防御激发将有助于研究我们实验室研究的困难但经济上更重要的谷物锈病病理系统。保守的真菌成分对效应剂的传递至关重要，是设计特定控制措施的主要目标，例如RNA沉默，为此我们在小麦中开发了一种抗锈病的策略。鉴定出的抗性基因可以用于育种计划，宿主效应靶基因可以通过基因组编辑进行修饰，从而使作物获得持久的抗病能力，减少对有害农药的依赖。**

Effector biology, the study of small secreted proteins from microbial pathogens, is a burgeoning research field in both human/animal and plant sciences. Studying effectors has already revealed insight into ways these proteins interact with and manipulate many basic host processes and signaling pathways. Effectors target development, protein degradation and gene regulation which include defense and resistance responses. Therefore, effectors teach us how pathogens cause disease but can also be used as probes to elucidate basic biological processes. ***Fungi have large suites of effectors, revealed by genome sequencing projects, but their mode of delivery, host cell targets and functions remain largely unknown. Having contributed to the generation and analyses of genome sequences of several cereal-infecting Basidiomycete pathogens (barley smut fungus Ustilago hordei and the related wheat leaf rust fungus Puccinia triticina), we can now focus on functions of the many predicted effectors. ***We recently identified in U. hordei an effector that triggers defense when infecting a barley cultivar with resistance gene Ruh1. This avirulence effector UhAVR1 is only expressed upon contact with the host, is secreted from the fungus, and its interaction with Ruh1 or its action leads to local host cell death and immunity to the infection. We genetically located Ruh1 on the short arm of barley chromosome 1 to a ~200-kb region. ******This proposal aims to shed light on 3 basic questions: ***1. What are the mechanisms of UhAVR1 secretion and determinants for host cell uptake? ***2. What is the function of UhAVR1 in barley cells, is it a real virulence factor, what host cell process or protein does it target? ***3. How does UhAVR1 interact with Ruh1 and cause immunity and can we isolate Ruh1? ******Elucidating mechanisms of effector delivery, identification of their host target(s) and defense elicitation in this model system will aid studying difficult, yet economically more important cereal rust pathosystems also studied in our laboratory. Conserved fungal components essential for effector delivery are prime targets for designing specific control measures such as RNA silencing for which we have developed a strategy in wheat against rusts. An identified resistance gene can be used in breeding programs and host effector target genes can be modified by genome editing to obtain durable disease resistance in crop plants and less reliance on harmful pesticides. **