Antioxidant enzymes in Nicotiana cells containing an Ipomoea peroxidase gene

The levels of the antioxidant enzymes, peroxidase (POD), superoxide dismutase (SOD), catalase (CAT) and glutathione reductase (GR), were investigated in seven cell lines (referred to as transgenic tobacco cell lines) derived from transgenic tobacco (Nicotiana tabacum) plants carrying a sweet potato (Ipomoea batatas) anionic POD cDNA (swpa1). Transgenic tobacco cell lines were induced from the leaf tissues of transgenic plants on MS medium supplemented with 1 mg l-1 2,4-D. A novel isoenzyme encoded by the swpa1 cDNA was detected on the native-PAGE in all transgenic tobacco cell lines. Average POD activity in transgenic cell lines was ca 1.3 times higher than that of control cell lines, whereas the other three antioxidant enzymes showed a slightly lower level in transgenic cell lines. The POD specific activity in each transgenic cell line had a high correlation with that of leaves in the original transgenic plants (r = 0.63). The ratio of in vitro cell lines to plant leaves in specific activities of four antioxidant enzymes showed a considerable difference: 2.5 in POD activity, 2.1 in SOD activity, 0.05 in CAT activity and 0.9 in GR activity. These results suggest that the antioxidative mechanism between in vitro cultured cells and intact plants may be differently regulated.ope