Differences in TOR and Yak1 Gene Expression in the Mold and Yeast Phases of Penicillium marneffei

Abstract

The study was conducted on the fungus Penicillium marneffei. Penicillium marneffei is endemic to south-east Asia and is the only thermally dimorphic species of the Penicillium genus. In its yeast form, it causes a systemic disease called Penicilliosis in immunocompromized individuals. It is currently treated by using moderately effective drugs like Amphotericin B. The dimorphic switch that changes the mold to yeast at 37 °C remains a mystery and could hold the key to designing effective treatments. Dimorphism could be hypothesized to depend on turning on or off certain genes like cell division or cell growth genes. The chief cell growth gene studied for this project is TOR or Target of Rapamycin. It is investigated for differential gene expression in the Mold and Yeast phases of the P. marneffei cells caused by the environmental stress. Also, the cells were treated with rapamycin to inhibit TOR and notice its effect on cell growth. TOR is characterized using bioinformatics analysis. Morphological study is conducted on un-treated and treated cultures using phase contrast microscopy. Cells are collected to extract RNA from the different samples and cDNA is synthesized. To study expression in real time, Quantitative Reverse Transcriptase Polymerase Chain Reaction (qRT-PCR) is performed on the samples using Actin and Calmodulin as controls. The expression of TOR increases in the yeast phase in both untreated and rapamycin treated P. marneffei cells even though the growth is severely stunted. This indicates the presence of a compensatory mechanism by which the cells try to survive the Rapamycin in the medium and remain mostly in filamentous form. Therefore, TOR could be playing a critical role in bringing about the dimorphic change and could aid to devising enhanced treatments for Penicilliosis.