| To characterize the biological effects of space radiation environment protons,in this project,we processed Arabidopsis wild type（WT）,microgravity signaling-deficient mutant（pin2）and radiation-sensitive mutant with defective anthocyanin synthesis（ttg1）using a new-generation spacecraft for 69 hours in mid-earth orbit,and analyzed the growth and development and the functional genomic change characteristics of ROS and DDR after returning to ground storage for 182 days.The results of the study were as follows:（1）Phenotypically,both wild type and pin2 and ttg1 mutants showed shorter germination rate,root length and flowering period（p<0.05）compared to their ground controls reflecting changes in low-dose radiation-stimulated traits.Root tip tissue ROS accumulation showed some increase in O2-,corresponding to a significant decrease in H2O2content compared to the control（p<0.01）.（2）In terms of functional gene GO enrichment analysis,it was found that wild-type Arabidopsis mainly exhibited down-regulated expression of genes involved in metabolic functions,but up-regulated expression of genes functional in cellular responses to external stimuli and other stress resistance functions;the pin2 mutant showed similar expression pattern as wild-type,but initiated the expression of more stress resistance and metabolic function genes,while the ttg1 mutant showed up-regulated expression of genes related to nucleotide biosynthesis and methyltransferase The ttg1 mutant showed upregulated expression of genes related to nucleotide biosynthesis and methyltransferase.Biological metabolic pathway analysis revealed that both wild type and ttg1 mutant were enriched to three biological pathways such as circadian rhythm,amino acid biosynthesis and metabolic pathway,while pin2 mutant was enriched to photosynthesis and steroid biosynthesis pathway.（3）Analysis of the expression network of ROS and DDR-related regulatory genes showed that the wild-type endogenous ROS repair functional genes were expressed more than the pin2 and ttg1 mutants,and the corresponding ROS production and transmission-related genes did not change,while the pin2 and ttg1 mutants had less expression of ROS repair functional genes functional genes,and their endogenous ROS production and transmission functional genes were still continuously expression.The corresponding DDR repair pathway functional genes,exhibited a certain number of DNA damage repair genes still showed down-regulated changes in wild type,while pin2 and ttg1 mutants did not show changes in the corresponding genes.（4）Bioinformatic methods were used to obtain 70 ROS genes associated with early flowering and identified the pivotal genes T21B4.20,DEAR3,BGLU33,BEL1,and IDA,among which DEAR3 combines the DRE/CRT cis-core action element to regulate the expression of ROS scavenging-related genes and antioxidant enzyme activities in Arabidopsis,and this gene is also GLU33,BEL1 and T21B4.20 are all genes involved in stress resistance regulation,and they were found to be involved in the stimulatory effect of shortened flowering period in Arabidopsis in this study..Further,the changes in functional genes corresponding to the NEO were compared,showing that the NEO induced stronger expression genes of ROS and DDR pathway due to the presence of a larger proportion of heavy ions,and the mid-earth orbit was mainly endogenous ROS induced by protons,which mainly stimulated the stimulatory effects of shorter flowering period,increased germination rate and root length. |
