Arsenate reduces copper phytotoxicity in gametophytes of Pteris vittata

• DOI: 10.1016/j.jplph.2008.04.008
• Publication Date: 2008-06-07T08:50:06Z
• Authors: Yongqiang Zheng; Xiaojing Dai; Lei Wang; Wenzhong Xu; Zhenyan He; Mi Ma
• Keywords: Chlorophyll; 0106 biological sciences; Cell Membrane Permeability; Copper Sulfate; Cell Survival; Pteris; Adaptation, Physiological; 01 natural sciences; Germ Cells; Arsenates; Tissue Distribution; Copper; Subcellular Fractions

The fern Pteris vittata is an arsenic (As) hyperaccumulator and can take up very high concentrations of arsenic from the soil. However, little is known about its response to co-contamination with arsenic and copper (Cu). In this study, we used an in vitro model system of P. vittata gametophytes to investigate the impact of changes in As and Cu status on growth, chlorophyll (chl) concentration, metal accumulation, and subcellular localization. A remarkable inhibition of growth occurred when gametophytes were exposed to concentrations >or=1.0mM Na(3)AsO(4) or >or=0.5mM CuSO(4). chl concentration decreased significantly when gametophytes were exposed to >0.25mM of CuSO(4), but increased steadily with concentration to <or=2mM Na(3)AsO(4). Interestingly, the inhibitory effect caused by Cu was reduced in the presence of 0.25mM Na(3)AsO(4). However, the inhibition caused by exposure to 1.0mM Na(3)AsO(4) was not alleviated by 0.25mM CuSO(4). Further studies showed that 0.25mM Na(3)AsO(4) increased cell viability (CV) and chl concentration, while decreasing cell membrane permeability (CMP) of gametophytes with 1.0mM CuSO(4) stress. In contrast, 0.25mM CuSO(4) decreased CV and chl concentration, while increasing CMP when gametophytes were treated with 1.0mM Na(3)AsO(4). In addition, the subcellular distribution of As and Cu in P. vittata gametophytes differed. As was found primarily in the cytoplasm, while Cu was mainly localized in the cell wall. These results suggest that As can reduce Cu phytotoxicity in the As hyperaccumulator P. vittata, and that this may serve as a biological mechanism for the fern to adapt to soils co-contaminated with As and Cu.