Transcriptomic Analysis of Nonylphenol Effect on Saccharomyces cerevisiae

Nonylphenol (NP), is a bioaccumulative environmental estrogen that is widely used as a nonionic surfactant. We have previously examined short-term effects of NP on yeast cells using microarray technology. In the present study, we investigated the long-term impacts of NP on Saccharomyces cerevisiae BY4742 cells by analyzing genome-wide transcriptional profiles using RNA-sequencing. We used 2 mg/L NP concentration exposure for 40 days. Gene expression analysis showed that a total of 948 genes were differentially expressed. Of these, 834 genes were downregulated, while 114 genes were significantly upregulated. GO enrichment analysis revealed that 369 GO terms were significantly affected by NP exposure. Further analysis showed that many of the differentially expressed genes were associated with oxidative phosphorylation, iron and copper acquisition, autophagy, pleiotropic drug resistance and cell cycle progression and related processes such as DNA and mismatch repair, chromosome segregation, spindle checkpoint activity, and kinetochore organization. Overall, these results provide considerable information and a comprehensive understanding of the long-term effects of NP at the gene expression level. Yeast cells were exposed to 2 mg/L nonylphenol (NP) for 40 rounds. The first round of the long-term exposure was initiated by adding NP to the cultures to reach final concentrations of 2 mg/L NP at the beginning of incubation. At the end of 22 hour of exposure, 1 mL sample was taken from each of the cultures, centrifuged, and supernatants were discarded. The precipitated cells were suspended in 1 mL of liquid YPD medium. This process was repeated three times to remove possible NP residuals. After the washing procedure, suspended cells were transferred to the new 100 mL YPD in 500 mL flasks and NP was added to the cultures to reach the above mentioned final concentrations of NP, and the second round of the exposure was initiated. The long-term exposure was performed for 40 rounds by repeating the above steps.