Effects of Tricyclazole on Cadmium Tolerance and Accumulation Characteristics of a Dark Septate Endophyte (DSE), Exophiala pisciphila.

ABSTRACT

Exophiala pisciphila is a cadmium-tolerant fungus, and produces 1,8-dihydroxynaphthalene melanin which can be inhibited by tricyclazole. Tricyclazole at higher levels (20 and 40 µg mL−1) reduced the growth and sporulation of E. pisciphila, but toxicity was not observed at a low concentration (2.5 µg mL−1). Under cadmium (Cd) stress (50, 100 and 200 mg L−1), 2.5 µg mL−1 of tricyclazole reduced fungal growth and sporulation. These reduces indicated a decrease on Cd tolerance of E. pisciphila. For both the 0 and 2.5 µg mL−1 tricyclazole treatments, Cd was associated mostly with cell walls and was extracted by 2 % acetic acid and 1 M NaCl. The FTIR spectra of the E. pisciphila mycelia were similar for both 0 and 2.5 µg mL−1 tricyclazole treatments, which showed hydroxyl, amine, carboxyl and phosphate groups. Thus inhibition of melanin synthesis by tricyclazole did not change Cd accumulation characteristics in E. pisciphila. Results suggested that melanin played a protective role for E. pisciphila against Cd stress, but inhibition of melanin synthesis did not have a remarkable impact on Cd accumulation in E. pisciphila.