The effect of EFG1 gene silencing on down-regulation of SAP5 gene, by use of RNAi technology.

Efg1 transcription factor is believed to be the main regulator of hyphal formation under many different conditions. In addition, it is responsible for positive regulation of the expression of several hyphal-specific genes. SAP5, which encodes secreted aspartic proteinase, is one of the mentioned genes and is crucial for pathogenicity properties. In the present work we have established the experimental conditions for the use of siRNA in the diploid yeast Candida albicans in order to knock-down the EFG1 gene expression as well as the Efg1-dependent gene, SAP5. The 19-nucleotide siRNA was designed according to cDNA sequence of EFG1 gene in C. albicans and modified-PEG/LiAc method was applied for yeast transfection. To quantify the level of both EFG1 and SAP5 gene expression, the cognate mRNAs were measured in C. albicans by quantitative real-time RT-PCR and data was consequently analyzed by use of REST® software. Images taken by fluorescent microscopy method indicated the effectiveness of transfection. According to REST® software data analysis, expression of EFG1 gene decreased about 2.5-fold using 500 nM of siRNA. A 7-fold decrease in EFG1 gene expression was observed when applying 1 µM of siRNA (P<0.05). Consequently, the expression of SAP5 was significantly down-regulated both in yeast treated with 500 and 1000 nM of siRNA (P<0.05). In conclusion, post-transcriptional gene silencing (PTGS) is likely to be considered as a promising approach to discover new gene targets so as to design fungal-specific antifungal agents, and it is strongly possible that we are taking the right way to battle with C. albicans-associated infections.