Transcriptional Analysis of Chlorella Pyrenoidosa Exposed to Bisphenol A

Bisphenol A (BPA) is the raw material of 71% of polycarbonate-based resins and 27% of epoxy-based resins which are used for coating metal-based food and beverage cans. Meanwhile, it is taken into account as a typical environmental pollutant. Hormesis may occur in algae exposed to BPA. In this study, the effects of BPA on Chlorella pyrenoidosa were assessed based on growth inhibition and transcriptome analysis. We have focused on two exposure scenarios as follows: (1) exposure to a low stimulation concentration (0.1 mg.L^-1, 19.35% promotion in cell density on the 3rd day); (2) exposure to a high inhibition concentration (10 mg.L^-1, 64.71% inhibition in cell density on the 3rd day). Transcriptome analysis showed enrichment in nucleotide transport, single-organism transport, cellular respiration. Among them, adenosine triphosphate (ATP) synthase and Nicotinamide adenine dinucleotide (NADH) dehydrogenase were upregulated under 0.1 mg.L^-1 BPA treatment. These changes enhanced the physiological and energy metabolic pathways of C. pyrenoidosa, thereby stimulating cell proliferation. At exposure to the high BPA, severe inhibited changes in the expression levels of several pathways were observed, which were related to tricarboxylic acid (TCA) cycle, glycolysis, fatty acid metabolism, oxidative phosphorylation, and photosynthesis. Therefore, BPA could negatively affect growth inhibition through the multiple energy metabolism processes. These results may result in a deeper insight into BPA-induced biphasic responses in algae, and provide vital information to assess the potential ecological risks of exposure to BPA in an aquatic ecosystem.