Investigation of the effects of weak acid stress on the cell cycle and transcription of cyc1 and gpd1 genes

Microorganisms secrete various organic acids, such as citric acid, lactic acid, acetic acid, and succinic acid, to their growth medium as a result of their metabolic activities. The type of these acids can vary depending on the microorganism's species. In this research, the effects of citric acid, lactic acid, and acetic acid on the transcription of GPD1 and CYC1 gene was investigated in S. cerevisiae. Besides, the effects of these organic acids on the cell division were also analyzed. Cytochrome C-1 (CYC1) gene encodes cytochrome C-isoform 1 peptide, which involves in the electron transfer chain in mitochondria and activation of apoptosis. GPD1 gene encodes NAD-dependent glycerol-3-phosphate dehydrogenase enzyme required for the redox balance (NAD/NADH ratio) and also catalyzes an essential step in glycerol biosynthesis in yeast. The results of this study indicated that citric acid represses the transcription of the CYC1 gene, but it activates the transcription of the GPD1 gene up to 3 to 4-fold. Acetic acid that activates apoptosis represses the transcription of CYC1 and GPD1 genes at significant levels. Moreover, our results indicated that citric acid-dependent activation of GPD1 transcription completely depends on the protein kinase Hog1p. Unlike Hog1p, it seems that the stress-activated transcription factors Msn2p, War1p, and Haa1p are not required for the activation of GPD1 gene transcription. Also, it appears that citric acid stress also results in abnormal cell division in S. cerevisiae. Altogether, the results of this research indicated that weak acid stress affects the transcription of GPD1 and the CYC1 gene and cause abnormal cell division in S. cerevisiae.