Biokemija izoprenidov in signaliziranje pri halofilnih in mezofilnih glivah (Slovene)

Molecular mechanisms that enable halophilic black yeasts, recently isolated from the salterns in Sečovlje, Slovenia, to addapt to high saline environments will be studied. Alteration in membrane properties as a way of addaptation to extreme conditions are well known.We will focused our innitial studies to the alterations in membrane properties as a consequence of changes in membrane lipids, particularly in sterol composition. Regulation of sterol biosynthesis through the modulation of the activity of its main regulatory enzyme 3-hydroxy-3-methylglutaryl CoA reductase (HMG R) as a response to high salinities, will be investigated. In addition to membrane lipids, isoprenilated proteins, especially those, involved in the transmission of hyperosmolar signalls in halophilic black yeasts will be studied. Our ultamate goal is to identify, at the level of transcriptome as well as proteome those genes and their products that are characteristically expressed at extremely high salinities. Part of our studies will be devoted to the steroidogenesis at the post-sterol level by investigating 17beta hydroxysteroid dehydrogenase (17b-HSD). This enzyme has been studied at the level of DNA as well as at the protein level in filamentous fungi in our group earlier. Characteristics and activity of 17b-HSD will be tested in halophilic black yeasts. The proposed experiments will contribute to the elucidation of the roll od 17b-HSD in eucariotic microorganisms in general and also to the evolution of this enzyme.