Studio dei meccanismi molecolari coinvolti nella transizione dimorfica inPichia fermentans

Pichia fermentansDiSAABA 726 is a dimorphic yeast that under yeast-like form controls brown rot on apple fruit, but shows pseudohyphal growth and a pathogenic behaviour on peach. With the aim of evaluating whether pseudohyphal growth represents a risk factor connected to the use of dimorphic yeasts as microbial antagonists in postharvest, the objective of the thesis was the isolation of the genes involved the yeast-like/pseudohyphae dimorphic shift in DiSAABA 726. To do that, the individuation of the nutritional factors able to induce and separate yeast-like and pseudohyphal growth was followed by the utilization of a Rapid Subtraction Hybridization approach for cloning differentially expressed genes. Results show that DiSAABA 726 changes morphology according to nitrogen source. RaSH approach highlighted six genes that are over-expressed in DiSAABA 726 during pseudohyphal growth. One of these, that matches to phospholipase C (CaPLC1) ofCandida albicans, seems of particular interest. In fact both its frequency of retrieval and the function of this protein inC. albicansandSaccharomyces cerevisiaestrongly suggest its involvement in DiSAABA 726 dimorphic transition. Moreover the inhibition ofpseudohyphaeformation in the presence of a known inhibitor of CaPlc1p, confirms the role of this protein in the dimorphic transition of DiSAABA 726. Thus Plc1p is a molecular target that can be used to evaluate whether the formation of pseudohyphae is associated with pathogenicity.