Fig. 4

Heavy metal enhanced the expression of EpTDC1, EpSNAT1, EpASMT1, and the accumulation of melatonin in E. pisciphila. The isolates were pretreated with 111.2 mg L^− 1 Cd²⁺, 100.0 mg L^− 1 Cu²⁺, 1010.0 mg L^− 1 Zn²⁺, and 800.0 mg L^− 1 Pb²⁺ respectively for 2 or 10 d. The relative expression of EpTDC1 (A), EpSNAT1 (B), and EpASMT1 (C) was analyzed by real-time RT-PCR, and the melatonin concentrations (D) were detected by HPLC. Data are means ± SD (n = 3). Columns with different letters denote significant differences at P < 0.05 according to Duncan’s multiple range test