Phytochelatin synthesis in Dunaliella salina induced by arsenite and arsenate under various phosphate regimes

This study investigated the dynamic variations in thiol compounds, including cysteine (Cys), glutathione (GSH), and phytochelatins (PCs), in Dunaliella salina samples exposed to arsenite [As(III)] and arsenate [As(V)] under various phosphate (PO43-) regimes. Our results showed that GSH was the major non-protein sulthydryl compound in D. saline cells. As(III) and As(V) induced PC syntheses in D. salina. PC2, PC3, and PC4 were all found in algal cells; the PC concentrations decreased gradually while exposed to As for 3 d. The synthesis of PC2-3 was significantly affected by As(III) and As(V) concentrations in the cultures. More PCs were detected in the As(V)-treated algal cells compared with the As(III) treatment. PC levels increased with As(III)/As(V) amount in the medium, but remained stable after 112 mu g L-1 As(V) exposure. In contrast, significant (p < 0.001) positive correlations were observed between PC synthesis and intracellular As(III) content or As accumulation in As(III)-treated algal cells during the 72-h exposure. PO43- had a significant influence on the PC synthesis in algal cells, irrespective of the As-treated species. Reductions in As uptake and subsequent PC synthesis by D. salina were observed as the PO43- concentration in the growth medium increased. L-Buthionine sulfoximine (BSO) differentially influenced PC synthesis in As-treated D. salina under different extracellular PO43- regimes. Overall, our data demonstrated that the production of GSH and PCs was affected by PO43- and that these thiols played an important role in As detoxification by D. salina.