Characterization of Cu and Zn ResistantNicotiana plumbaginifoliaSuspension Cultures

摘要

The mechanisms of Cu and Zn resistance in culturedNicotiana plumbaginifoliacells were investigated. When crude extracts of both the Cu and Zn resistant cells were passed through Sephadex G-75 gel filtration columns, two metal containing peaks were identified. In each case the Cu or Zn was associated with a high molecular weight fraction (ca. 70,000) and a low molecular weight fraction (less than 3,000) with the majority being associated with the low molecular weight fraction. The low molecular weight fraction in particular increased upon exposure of the cells to the metals.Both the Cu and Zn resistant cells accumulated higher levels of citrate and malate than the wild type cells in the presence of the metals. The addition of citrate or malate, but not fumarate or succinate to the culture medium prevented Cu or Zn toxicity to wild type cells. These results suggest that theN. plumbaginifoliacells selected as resistant to Cu or Zn are resistant, at least in part, because of their ability to accumulate the chelators, citrate and malate, in the presence of the metals.