Abstract
Cells of
Catharanthus roseus (L.) G. Don were maintained and sub-cultured in the absence of NaCl (control) or were sub-cultured for 7 days in the presence of 50
mM (“50”) or 100
mM (“100”) NaCl, or were maintained and sub-cultured for 8 months in the continuous presence of 50
mM NaCl (“50T” or salt-adapted cells). Exposure of cells to salt treatment reduced growth in a concentration-dependent manner. Salt-treated cells strongly accumulated Na
+ and, to a lesser extent, Cl
−. However, no significant change in Cl
− accumulation was observed in 50T cells.
Salt progressively increased superoxide dismutase (SOD) and ascorbate peroxidase (APX) activities whereas a strong increase in catalase (CAT) activity was only obtained in 50 and 50T cells. SOD activity was lower in 50T than in 50 cells, whereas the opposite was observed for APX activity.
After native polyacrylamide gel electrophoresis (PAGE) analysis, five SOD isoenzymes were detected and the increase in SOD activity observed in salt-treated cells seemed to be mainly due to isoenzymes (SOD 1, 2 and 3). Three APX isoenzymes (APX 1, 2 and 3) were detected markedly, especially in salt-adapted cells. Salt strongly induced CAT 2 isoenzyme in 50 cells and CAT 1 isoenzyme in 50T cells.
These data suggest that salt treatment provoked an oxidative stress in
C. roseus cells, as shown by the increase in lipid peroxidation, in spite of the induction of antioxidant enzymes. This increase in lipid peroxidation was paralleled by a rise in lipoxygenase (LOX) activity.
Increases in antioxidant activities could also be a response to the cellular damage provoked by NaCl. Probably, this increase could not stop the deleterious effects of salt, but reduced stress severity thus allowing cell growth to occur.