Physiological Responses Of Exogenous Si And NO To Wheat Seedlings Under Copper Stress And Differential Expression Of Related Mirna

In order to investigate the effects of silicon(Si)and nitric oxide(NO)on wheat seedlings under copper(Cu)stress,wheat was used as materials.Physiological characteristics and miRNA were measured by adding Si and NO under Cu stress.The results of the study are as follows:1.The root length,root surface area,root volume,root activity,chlorophyll content and chlorophyll fluorescence of wheat seedlings significantly decreased under the stess of Cu,and the longer the time was,the larger the decrease was,but the average diameter of root increased.The contents of Cu,Si,and Fe in roots increased,but the contents of Ca,K,Mg,Mn and Zn decreased,while the contents of Na first increased and then decreased.Supply of exogenous Si and NO under Cu stress significantly promoted the root activity,length,surface area,volume and chlorophyll content,chlorophyll fluorescence and contents of nutrients(Ca?K?Mg?Mn?Zn)of wheat seedlings.At the same time,the average root diameter in plants were reduced significantly,so exogenous silicon and nitric oxide can improve the tolerance of wheat seedlings to Cu stress.In addition,there were a significant positive correlation between Mg-Zn and Si-Na,and a significant negative correlation between Cu-Mn and Cu-Mn,indicating that synergistic or antagonistic effects were dominant among these elements.In conclusion,exogenous Si and NO can alleviate the stress of heavy metal Cu on wheat seedlings to some extent,and Si was more effective than NO.2.The miRNA sequencing analysis of exogenous Si and NO under copper stress showed that 99 and 88 differentially expressed miRNAs were detected by exogenous Si and NO treatments after 48 h treatment.Under the treatment of Si,58 miRNAs such as miR894,miR156 and miR396 were up-regulated in different degrees,and 41 miRNAs such as miR159,miR160 and miR393 were down-regulated to varying degrees.Under NO treatment,26 miRNAs including miR894,miR531 and miR482 were up-regulated to varying degrees,and66 miRNAs including miR396,miR159 and miR166 were down-regulated to varying degrees.These results indicated that these differential miRNAs are involved in the regulation of exogenous Si and NO responses to copper stress.After GO enrichment analysis of target genes predicted by miRNAs,it was found that these genes were enriched in biological processes such as redox reaction,metal ion binding,and protein kinase and so on.Theanalysis of KEGG pathways revealed that these genes also be involved in a variety of biological processes such as photosynthesis,glutathione metabolism,and plant hormone signal transduction,and play an important role in regulating copper stress responses.3.Transcriptome sequencing was performed on exogenous Si and NO under copper stress,and 6445 and 8173 differentially expressed mRNAs were detected in exogenous Si and NO treatments respectively.Combined analysis of differentially expressed miRNA and mRNA showed that 74 differentially expressed miRNA under exogenous Si treatment were associated with 773 target genes,and 58 differentially expressed miRNA under exogenous NO treatment were associated with 912 target genes.These findings help to elucidate the mitigation mechanism of exogenous Si and NO under copper stress from the molecular perspective.