Identification of Glutathione S-Transferase (GST) Genes from a Dark Septate Endophytic Fungus (Exophiala pisciphila) and Their Expression Patterns under Varied Metals Stress

Glutathione S-transferases (GSTs) compose a family of multifunctional enzymes that play important roles in the detoxification of xenobiotics and the oxidative stress response. In the present study, twenty four GST genes from the transcriptome of a metal-tolerant dark septate endophyte (DSE), Exophiala pisciphila , were identified based on sequence homology, and their responses to various heavy metal exposures were also analyzed. Phylogenetic analysis showed that the 24 GST genes from E . pisciphila ( EpGST s) were divided into eight distinct classes, including seven cytosolic classes and one mitochondrial metaxin 1-like class. Moreover, the variable expression patterns of these EpGST s were observed under different heavy metal stresses at their effective concentrations for inhibiting growth by 50% (EC 50 ). Lead (Pb) exposure caused the up-regulation of all EpGST s, while cadmium (Cd), copper (Cu) and zinc (Zn) treatments led to the significant up-regulation of most of the EpGST s ( p < 0.05 to p < 0.001). Furthermore, although heavy metal-specific differences in performance were observed under various heavy metals in Escherichia coli BL21 (DE3) transformed with EpGSTN-31 , the over-expression of this gene was able to enhance the heavy metal tolerance of the host cells. These results indicate that E . Pisciphila harbored a diverse of GST genes and the up-regulated EpGST s are closely related to the heavy metal tolerance of E . pisciphila . The study represents the first investigation of the GST family in E . pisciphila and provides a primary interpretation of heavy metal detoxification for E . pisciphila .