Investigation of antifungal drugs for effective use in fission yeast Schizosaccharomyces pombe

Fungal diseases caused by opportunistic fungal species, it is one of the leading causes of deaths, especially in individuals suffering from certain health problems or immunosuppressive therapy. The worldwide morbidity and mortality rate caused by invasive fungal infections from pathogenic fungal species such as Candida, Aspergillus, Cryptococcus and Pneumocystis poses a serious threat. There are three main classes of antifungal drugs used in the treatment of systemic fungal infections. These are azoles that target ergosterol biosynthesis, echinocandins that inhibit fungal cell wall biosynthesis, and polyenes that bind to ergosterol in the fungal cell membrane and cause cell lysis. Recently, the irregular, long term and careless use of these drugs has led to the resistance of pathogens over time. There are many underlying causes of antifungal drug resistance, including adaptive mechanisms such as drug target change or overexpression, upregulation of multiple drug transporters, and activation of stress responses. Within the scope of this thesis study, the roles of 19 new candidate genes and 5 fluconazole resistance-related gene from literature review, including fluconazole target erg11 gene, in antifungal drug resistance were investigated. In this context, ED666 parental strain of fission yeast (Schizosaccharomyces pombe), which shares much in common with pathogenic fungi, and 21 strains with deletions in various genes (SPAC22H10.09, bun107, mug166, nnt1, nas2, yih1, hrk1, SPAC4H1, rpb9sh) , qcr8, rsv2, srp14, clp1, bgs4 and plh1 rhp18, SPCC338.06c, SPBC27B12.05, phb2 and erg31) were considered as study material. In this context, the minimum inhibitory concentrations (MIC) of three different antifungal agents (fluconazole, tetraconazole and thiabendazole) in S. pombe ED666 strain were calculated separately and in combination with fluconazole and tetraconazole. A paradoxical effect was observed in which the cells continued to reproduce by changing the cell wall content at values above the MIC against fluconazole among these agents. In the further analyzes performed within the scope of this thesis, only the IC5 and IC10values, which are the concentrations at which the growth rate of fluconazole begins to change, were used in S. pombe ED666 wild type. Accordingly, while the transcription levels of some genes (SPAC22H10.09, bun107, mug166, nnt1, nas2, yih1, SPAC4H3.06, msh1, rpb9, qcr8, rsv2, erg6 ve erg9) were upregulated on IC5 dose, downregulated on IC10. In contrast, downregulated (srp14, clp1, bgs4 and phb2) and upregulated (plh1, erg11 and erg31) levels of the other genes were detected at both doses. No significant increase in ROT was observed in parental and mutant strains. This result is compatible with the low level of ROT in resistant strains. In conclusion, the relationship of SPAC22H10.09, bun107, mug166, nnt1, nas2, yih1, SPAC4H3.06, msh1, rpb9, qcr8, rsv2, srp14, clp1, bgs4, plh1 ve phb2 genes with drug resistance was revealed for the first time in this thesis study. It is suggested that downregulation of these genes also plays a role in resistance.