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Identification of a glutathione S‐transferase gene of Physarum polycephalum as a biomarker for nanosized TiO2 exposure under dark conditions

In this study, a glutathione S‐transferase gene (gst) from sensitive Physarum polycephalum was selected for its ability to detect nanosized TiO2 (nTiO2) exposure under dark conditions. The concentration of nTiO2 (25, 40 and 60 nm) for subsequent assays was first determined (5–18 mg ml−1) and total GST enzyme activity of P. polycephalum was confirmed to be increased 6–44 fold in groups treated with nTiO2. Second, an RNA‐seq study was performed to identify candidate gst genes before isolation of an optimum gst gene of P. polycephalum (Ppgst), which encoded 223 amino acids. Third, the transcriptional level of the Ppgst gene was further confirmed to be positively correlated with nTiO2 exposure within the concentration range of (5–15 mg ml−1) by qPCR. In conclusion, these results indicated that the transcriptional level of Ppgst can reflect nTiO2 exposure, suggesting that it may be employed as a new biomarker for nTiO2 pollution under dark conditions.