Ultrastructural localization of Ag-NOR proteins in root meristem cells after copper treatment

Abstract

Summary The effect of a 2-week exposure to various copper concentrations on the structure of nucleoli and ultra-structural localization of Ag-NOR proteins was investigated in root meristem cells of Zea mays. Transmission electron microscopy and silver staining were applied on interphasic nucleoli to measure the influence of copper on these parameters. Morphological results indicate that copper treatment induces alterations in the structure of the nucleoli, which was manifested by segregation of its main nucleolar components. After nucleolar segregation the nucleoli underwent a gradual degranulation, which was completed at the highest Cu concentration (78μmol/L). Morphometric analyses showed that with the increase of the Cu concentrations the nucleolar area decreases, whereas the Ag-stained are a increases, resulting in an increase in the Ag-stained/nucleolar area from 30 to nearly 100%. The results suggest that nucleolar morphological alterations in copper-treated root meristem cells are at least partly due to the copper effect on Ag-NOR proteins.