Molecular Analysis of Necrotrophic Mycoparasitism in the Predator Yeast Saccharomycopsis schoenii

点击翻译按钮获取中文摘要

Our work aims at the molecular analysis of predation in Saccharomycopsis schoenii.Saccharomycopsis species have strong potential because:(i) they can be easily cultivated, are haploid (our unpublished results), are either homothallic or heterothallic and are amenable to forward and reverse genetics.(ii) they show a unique property of necrotrophic mycoparasitism within Saccharomycetales that provides a simple model to study host-pathogen interactions, e.g. in combination with the powerful genetics of S. cerevisiae as a prey organism.(iii) they have a biphasic life-style. They grow saprophytic in full media but switch to a predatory life-style upon starvation. This will allow dissecting virulence genes from metabolic genes.(iv) Saccharomycopsis species may be useful as biocontrol organisms that could be employed in agriculture to reduce the amount of fungicides used to control plant pathogenic fungi. We propose four work packages within this project based on our extensive previous work:(i) The further characterization of the avirulent KSS1 deletion strain in order to answer the following questions:Is there any sensing of prey cells in the kss1 mutant? That is, do predator yeast kss1 cells still grow towards their prey? Are kss1 cells at all able to form penetration pegs? The complementation strain appeared to be better i.e. more virulent than the wildtype strain. Therefore, we will analyze if the expression level of KSS1 influences virulence?(ii) Study the predation process from the predator’s side, particularly by dissecting polarized morphogenesis and the actin cytoskeleton to monitor events that lead to penetration peg formation. We expect actin polarization to the tip of the penetration peg. Yet, of premier interest to us is if there is actin ring formation at the base of the penetration peg and further if there is a requirement of a nuclear division during penetration peg formation and the entry of a nucleus in the penetration peg. (iii) Characterization of the predation process from the viewpoint of the prey cell. This shall answer the key question whether (or for how long) the plasma membrane of the S. cerevisiae prey cells stays intact during predation. Here we will also analyse subcellular changes in prey cell compartments, e.g. the vacuole and the mitochondria using fluorescence microscopy.(iv) Analysis of additional components of the MAPK-signaling cascade in S. schoenii, particularly the MAP kinase FUS3 and the downstream transcription factor STE12. This shall answer the key question if and how predator yeasts prioritize between predation and mating.