Effect of foliar spraying of H2O2 and Cu/Zn SOD and APX gene transfered in chloroplasts on the recoverability of sweet potato after chilling stress

Abstract

【Objective】 In an experiment, the recoverability of the sweetpotato, which expressed both Cu/Zn superoxide dismutase (SOD) and ascorbate peroxidase (APX) in chloroplasts, was compared with its control plants after a short time of chilling stress, and foliar application of exogenous hydrogen peroxide (H2O2) before chilling stress on enhancement of seedling recovery capability after chilling stress was studied.【Method】 The transgenic sweetpotato that simultaneously expressed both Cu/Zn SOD and APX in chloroplast and its non-transgenic control plants were used as materials, and the recoverability of them after one night (12 h) of chilling stress at 5℃, and the enhancement of chilling resistance when pretreated them with 1.0 mmol·L-1 H2O2 before chilling stress, the membrane permeability, anti-oxidative enzymes system and photosynthetic system of each plant were tested in this experiment. 【Result】 Soon after a short time (12 h) chilling stress, the activity of anti-oxidative enzymes of SOD, AXP and CAT (catalase) in non-transgenic sweet potato decreased significantly and so did the content of carotenoid, but the membrane permeability increased significantly, photosynthetic pigment and photosynthetic electron transport chain were damaged, so the photosynthetic rate reduced. After 26 h of recovery at room temperature (25℃), the activities of the above three mentioned anti-oxidative enzymes and the content of carotenoid all increased significantly, membrane permeability kept a tendency of increase, and photosynthetic electron transport chain was almost repaired completely while photosynthetic pigment decreased significantly, but the photosynthesis recovered to a large extent. Compared with non-transgenic sweetpotato after chilling stress, it was observed that in transgenic sweetpotato, the activities of the above three mentioned anti-oxidative enzymes and the content of caroternoid were higher, membrane permeability was lower, and furthermore the transgenic sweetpotato had a stronger ability to protect photosynthetic pigment and photosynthetic electron transport chain, therefore, the photosynthetic rate was relatively high. It was also observed that in the recovery process of the plants treated with 1.0 mmol·L-1 H2O2 before chilling stress, compared with the non-treatments, the recovery capabilities of the anti-oxidative enzymes were stronger, the content of MDA and membrane permeability were lower, and the growth status after chilling was better. 【Conclusion】 A stronger chilling-resistance ability was showed in transgenic sweetpotato compared with non-transgenic sweetpotato under the treatment of chilling stress, and so did a stronger recovery capability after stress. So the introduced genes of Cu/Zn SOD and APX provided sweetpotato an advantage against chilling. The pretreatment with 1.0 mmol·L-1 H2O2 improved the recovery capability of the sweetpotato plants after stress, and the chilling resistance was enhanced.