Effect Of SJ-10 Satellite On Oryza Sativa Oxidative Stress

Oxidative stress can cause increase in active oxygen in plants and result in lipid peroxidation,affect the antioxidant enzyme activity and energy metabolism process.In order to explore the mechanism of space environment on plant mitochondrial oxidative stress,our subject put the seeds of rice Dongnong 423（DN423）on three different positions（SPA、SPB、SPC）of the Space Program SJ-10 recoverable satellite,and took a combination of height,antioxidant level,key enzyme gene expression to examine the response of rice in different growth stages.the relationship between mitochondrial dysfunction and biological effects of space radiation was studied in multiple layer and obtained the following results :1.Phenotypic study was carried by plant height.In trefoil stage,the rice height was increased than control groups whereas the rice height had no difference in tillering stage.After spaceflight,it had a low-dose stimulatory effect to rice growth and this effect was gradually restored with rice growth.2.The content of reactive oxygen species（ROS）was determined by DCF method.After spaceflight,the content of ROS was lower in the trefoil stage but higher in the tillering and maturation stages which indicated that the effect of oxidative stress happened at the early stage of rice growth and continued until the rice maturity.The difference of oxidative stress effect regular pattern between trefoil stage and other stages may be caused by the different expression of-related factors.3.The enzyme activity of oxidative stress-related enzymes was determined by spectrophotometry.It was found that in trefoil stage,the activities of superoxide dismutase（SOD）and ascorbate peroxidase（APX）were significantly higher in three flight groups compared to the corresponding control group which was consistent with the trend of ROS level.In tillering stage,the change trend of SOD was the same as ROS,however,the activity of APX was significantly lower in the SPB group than in the control group which indicated that in this s tage,the main factor was H₂O₂ and related to different radiation dose.The SOD activity in the SPA group was significantly lower than that in the control group during the maturation stage,indicating that the rice oxidative stress effect was mainly affect ed by other hydrogen peroxide scavenging enzyme activities during the mature period.Due to the main site of ROS production in plants is mitochondria,the enzymes encoded by mitochondrial related genes need further studied.4.The expression of mitochondrial oxidative stress-related enzymes genes was determined by RT-PCR method.The results showed that the expression of enzymes encoded by mitochondrial oxidative stress-related genes in each experimental group was not consistent with the level of antioxidant kinase activity and ROS content.It was speculated that the main sites for oxidative stress in the space flight group were not completely mitochondria,which may due to space flight had a greater impact on rice mitochondria itself so that affected the performance of oxidative stress.