Over expression of CuZn superoxide dismutase (CuZn SOD) and ascorbate peroxidase (APX) in transgenic sweet potato enhances tolerance and recovery from drought stress

Abstract

To understand the antioxidant stress of transgenic sweet potato containing elevated Cu/Zn superoxide dismutase (Cu/Zn SOD) and ascorbate peroxidase (APX) in chloroplasts, we analyzed plant growth, yield, water status, photosynthetic activity and several antioxidant enzyme activities under drought and post-drought re-watering conditions. Three water stress regimes - no, moderate and severe water stress - were applied. Our results indicated that the number of transgenic plants (TS) was a function of water deficit and recovery period. Compared with non-transgenic plants (NS), the expression of antioxidant enzymes (SOD, APX and CAT) in transgenic plants was profoundly increased under drought stress and rewatering periods. Transgenic plants exhibited better growth, photosynthetic activity (Fv/Fm) and water status under drought stress, but tuberization was poor. Compared with NS plants, TS plants exhibited low levels of malondialdehyde (MDA) and electrolyte leakage (EL). In addition, TS plants recovered faster upon release from drought stress. These results showed that expression of Cu/Zn SOD and APX in chloroplasts of sweet potato enhanced drought resistance and capacity for recovery from drought stress. However, tuber formation in TS plants was constrained by drought stress.

Key words: Transgenic sweet potato, antioxidant enzyme, drought, recovery.