Characteristics Of Chronic ROS Induced By Space HZE Ions Of Different LET In Rice

The space environment is a complex environment with multiple types of radiation.Space radiation can cause oxidative stress effects in the body,and space high energy heavy ions can cause greater radiation oxidative damage.In order to explore the energy effect of high-energy heavy ion(HZE)radiation on the endogenous reactive oxygen species in rice,this study carried out the whole-cycle culture treatment by stacking the Nipponbare rice seeds in the bio-radiation box carried on the Shijian-10.The ions hit the rice seeds for analysis.According to the LET value of the radiationenergy level parameter,the experimental group was divided into RN(unhit by HZE),R30(LET10-30KeV/?m),R60(LET30-601KeV/?m),R100(LET60-100KeV/?m),R200(LET100-200KeV/?m),R300(LET>200KeV/?m)groups.From the phenotype,photosynthetic efficiency,the expression of hydrogen peroxide and superoxide anion in reactive oxygen species,and the level of transcriptome sequencing,the energy effects of high-energy particles effects of space radiation were explored.Combining the experimental contents of the above several levels,the analysis results were as follows.After Shijian-10 space flight,the germination rate of each group was inhibited.In terms of morphology,there was no significant change in plant height during tillering after space flight,in terms of number of tillers,space radiation decreased the number of tillers of RN group and HZE radiation component,and significantly decreased at low energy level LET30-100KeV/?m.In terms of photosynthetic efficiency in the tillering stage,there was no significant difference in the maximum quantum yield Fv/Fm between spaceradiation group and the ground control.Hydrogen peroxide and superoxide anion were detected by a reactive oxygen species(ROS)fluorescent probe.Hydrogen peroxide staining results showed that both RN and HZE radiation groups had an upward trend compared to control especially at LET range of 100-200 KeV/?m.Superoxide anion staining showed a decrease in both RN group and HZE groups.The results indicated that the level of endogenous ROS induced by radiation was still high in tillering stage and persisted in chronic stage,mainly caused by hydrogen peroxide.For the transcriptomic analysis,space flight caused differential expression of large-scale genes.The number of differentially expressed genes at LET30-150 keV/?m showed an increasing trends as LET value.Among them,genes involved in the assembly and regulation of genetic material structure,nucleic acid metabolism and gene expression regulation showed obvious LET effects.The analysis of genes involved in ROS receptor transduction,production and clearance also indicated that ROS pathway transcription factors and cascade transduction signaling molecules showed dynamic change levels depending on LET values,ROS clearance pathway caused a wide range of removal of hydrogen peroxide gene responses.This study provides a theoretical basis for exploring the LET effect of space HZE radiation.