The effect of salt stress on lipid peroxidation and antioxidative enzymes in callus of two <Emphasis Type="Italic">Acanthophyllum</Emphasis> species

The changes in lipid peroxidation and the involvement of the antioxidant system in relation to salt stress tolerance were investigated in the callus of Acanthophyllum glandulosum and Acanthophyllum sordidum. The callus was subjected to NaCl stress (50–200 mM) for 40 d. The callus of A. glandulosum was less sensitive to NaCl stress than that of A. sordidum. Increasing concentrations of NaCl from 50 to 200 mM correlated to increased proline content in A. glandulosum. Total protein content was higher in extracts of A. glandulosum than in extracts of A. sordidum under both control and salinity treatments. Compared with A. sordidum, lipid peroxidation and H₂O₂ content were lower and the activities of superoxide dismutase (SOD), catalase (CAT), guaiacol peroxidase (GPX), ascorbate peroxidase, and glutathione reductase were higher in A. glandulosum under salt stress. Activity staining of antioxidant enzymes separated by native polyacrylamide gel electrophoresis (PAGE) revealed that callus of A. sordidum had five Fe-SOD isoforms and one Mn-SOD isoform, all of which were reduced by salinity. In A. glandulosum, two Mn-SOD, three Fe-SOD, and one Cu/Zn-SOD isoforms were detected. Out of these six SOD isoforms, expression of the Mn-SOD and Fe-SOD isoforms was enhanced at 100 mM and higher NaCl concentrations. Two and six GPX isoforms were detected in A. sordidum and A. glandulosum, respectively. Expression of the single CAT isoform in A. sordidum was preferentially reduced by salinity. In A. glandulosum, the two CAT isoforms showed differential down regulation under NaCl stress, with the CAT2 isoform detected only under control condition. These results suggest that A. glandulosum callus is better protected against salinity-induced oxidative damage by maintaining higher activities of antioxidant enzymes than the callus of A. sordidum.