The Effect Of PEG Pretreatment On Antioxidant Enzymes In Rice Isozyme And Its Expression Under Water Stress

Water stress is one of the main factors affecting plant growth, and is the major natural disaster of world agricultural production. In this context, study and improving the mechanism of resistance to water stress for rice has become one of the key issues needed to be solved.Using polyethylene glycol (PEG6000) to simulate water stress in the experiment, we have studied the effect of water stress on superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) isozyme and cu/znSOD, APX1 and CAT1 gene expression in the antioxidant defense system of rice leaves and roots with 10% PEG pretreatment and water recovery and another 15% PEG-simulated, and revealed methods and degree of the antioxidant enzymes in rice isozyme response to the PEG pretreatment. then researched the antioxidant enzymes in rice response to PEG pretreatment on the molecular level. and also provides the basis on improving drought resistance in rice. The results are as follows:In pretreated rice leaves. SOD isozymes will help the leaves to feel water stress much faster to protect the rice from harm. The research on rice roots found that enzymesâ…¡,â…¢have some resistance to water stress after pretreated. The activity of enzymesâ…¡in group (pre-15% PEG) without rehydration treatment is lower than the control group but higher than the group (pretreatment-rehydration-15% PEG) with pretreatment. The rehydration after pretreatment can help to re pare the SOD enzymesâ…¡in rice roots. Therefore, PEG pretreatment and water recovery can improve the ability of SOD isozymes in rice to resist water stress. Peroxidase (POD) isozymesâ…¦in rice leaves and the POD isozymesâ…£,â…¤in roots are all induced after pretreatment. In rice leaves, the overall activity of POD isoenzymes in pretreatment group (pretreatment-rehydration-15% PEG) is higher than the control group and other groups. Therefore, POD isozyme can feel faster and stronger to protect the rice from harm after pretreatment. Whether in rice leaves or in roots, the total activity of hydrogen peroxide (CAT) isozymes in group (pretreatment-rehydration-15% PEG) which is after PEG pretreatment is lower than that in group (direct 15% PEG) without PEG pretreatment, and the activity of CAT isozymes in group (pre-15% PEG) without rehydration treatment is higher than that in group (pretreatment-rehydration-15% PEG) with rehydration treatment. That means that water stress preconditioning may improve the ability of CAT isozymes in rice roots to re-stress response so that CAT isozymes show a similar reaction in control group when they are subjected to stress again. Besides, the rehydration process protects the CAT isozymes to some extent. Therefore, pretreatment can improve the ability of CAT isozymes in rice to response to water stress.Both in rice leaves and roots, the transcription levels of Antioxidant enzyme genes like cu/ znSOD, APX1 and CAT1 after pretreatment significantly increased than those without pretreatment when they are subjected to water stress. This shows that PEG pretreatment can improve the ability of rice to resist to water stress on the level of gene expression. At the same time, the rehydration phase after PEG pretreatment repares the antioxidant gene expression in rice. That is to say, the rehydration phase after PEG pretreatment plays an important role in the recovery of defense mechanism in rice root.