Functional genomics of the biocontrol agent-plant pathogen interaction pseudozyma flucculosa-powdery mildews

通过利用天敌或通过诱导植物的自然防御机制对植物病原体进行生物防治的实际应用，前提是彻底了解这些现象背后的遗传、分子和生态事件。在过去20年里，这一挑战一直是申请人实验室开展的研究活动的焦点。在上一期中，我们在阐明控制白粉病真菌天然拮抗剂--絮状假丝酵母生防特性的复杂因素方面取得了一些重大进展。有特殊意义的是，我们报道了以下内容：1)绿色荧光蛋白转化子的发展，以研究丛生疫霉-植物-白粉病的三营养交互作用；2)BCA分泌的重要次生代谢物--絮凝素对医学上重要的病原菌的抗真菌和抗菌活性；3)一种新的转化假酵母菌的技术的发展；4)BCA对絮状菌素的分解活性的发现和描述；5)通过蛋白质组和基因组分析鉴定与丛生疫霉的特定生控活性相关的营养和生态因素；6)发现了涉及絮凝素生物合成的基因和基因簇，并与系统发育相关的植物病原菌模式真菌--玉米黑粉菌建立了不经意间的紧密联系。后一项成就被认为是一项重大突破，因为它开辟了一条道路，1)基于已测序的玉米粉菌基因组，特权地观察丛枝孢子菌的基因组；2)比较功能基因组分析，将定义使真菌成为有益的BCA或植物病原体的微妙的遗传和进化事件。在这一应用的背景下，在我们最新进展的基础上，目标是：1)完成絮状拟酵母菌的基因组组装；2)对丛生拟酵母菌基因组进行注释，特别是调控小球菌素合成的基因簇和调控玉米小球藻利用合成的相似簇；3)进行比较功能基因组分析，目的是确定赋予丛生拟酵母菌和玉米小蜂不同生活方式的特定成分。这些目标的实现将产生关于以下方面的新的和独特的信息：调节簇毛拟青霉对白粉病真菌的生防活性的遗传决定因素；这些决定因素的表达(或抑制)如何影响真菌生态。这些结果将对植物病理学领域产生深远的影响，因为我们的模型将为分离和调节两种系统发育相关的真菌作为生防剂或植物病原体的内在遗传因素提供独特的数据。

Practical application of biological control of plant pathogens, either through the use of natural enemies or through the induction of the plant's natural defense mechanisms, presupposes a thorough understanding of the genetic, molecular and ecological events underlying such phenomena. This challenge has been the focal point of the research activities carried out in the applicant's laboratory over the last 20 years. In the previous installment, we have made some major strides toward elucidating the complex factors governing the biocontrol properties of Pseudozyma flocculosa, a natural antagonist of powdery mildew fungi. Of particular significance, we reported the following: 1) the development of GFP-transformants to study the tritrophic interaction P. flocculosa-plant-powdery mildew ; 2) the antifungal and antibacterial activity of flocculosin, an important secondary metabolite secreted by the BCA, against pathogen strains of medical importance; 3) the development of a novel technique to transform Pseudozyma spp.; 4) the discovery and description of catabolitic activities by the BCA against flocculosin and 5) identification of nutritional and ecological factors linked with the specific biocontrol activity of P. flocculosa through proteomic and genomic analyses; and 6) discovery of genes and a gene cluster involved in flocculosin biosynthesis and establishment of an unsuspected close link with the phylogenetically related plant pathogen model fungus Ustilago maydis. This latter achievement is perceived as a major breakthrough since it opens the way to 1) a privileged look into the genome of P. flocculosa based on the sequenced genome of U. maydis and 2) to comparative functional genomic analyses that will define the subtle genetic and evolutive events that make a fungus a beneficial BCA or a plant pathogen. In the context of this application and on the basis of our recent progress, the objectives are: 1) to complete the genome assembly of Pseudozyma flocculosa; 2) to carry out genomic annotation of P. flocculosa with particular emphasis on the gene cluster regulating flocculosin synthesis and the similar cluster regulating ustilagic synthesis in U. maydis; and 3) to conduct comparative functional genomic analyses with the aim to identify the specific components that confer different lifestyles to P. flocculosa and U. maydis. Fulfillment of these objectives will generate novel and distinctive information with regards to: the genetic determinants that regulate the biocontrol activity of P. flocculosa against powdery mildew fungi; how expression (or repression) of these determinants influence the ecology of fungi. These results will have far reaching impact into the field of plant pathology as our model will provide unique data into the intrinsic genetic factors that separate and modulate two phylogenetically related fungi to behave as biocontrol agent or plant pathogen.