Metal-tolerant moss Scopelophila cataractae accumulates copper in the cell wall pectin of the protonema

The growth kinetics in the presence of copper (Cu) of the protonema of the moss Scopelophila cataractae and the matrix polysaccharides of its cell walls have been analyzed in this study. Protonemal cells cultured in a medium containing 0.2 mM CuSO4 showed a rapid accumulation of Cu, reaching a maximum between 30 and 60 d at approximately 65 μmol g−1 DW. Uronic acids were found in similar amounts in cell walls of both control and Cu-treated cells, whereas arabinose and galactose decreased to 61–67% in the presence of Cu. Cell wall polysaccharides were determined after successive extraction with 50 mM CDTA, 50 mM Na2CO3, 1 M KOH, and 4 M KOH. The pectic fractions (CDTA- and Na2CO3-soluble) decreased to 47% and the hemicellulosic fractions (1 M KOH- and 4 M KOH-soluble) to 86% under Cu application. Approximately 43% of the Cu taken into cell walls was released following endo-pectate lyase treatment, suggesting that two-fifths of the total Cu accumulation was tightly bound to the homogalacturonan of the cell wall pectin.