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

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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.