Abstract: MSH6 plays an important role in the activation of checkpoints in cell cycles and in repairing of DNA damage under Cd stress. In this study, we found that MSH6 gene had targeting sequence of microRNAs (miRNAs), including miRNA172b-5p, miRNA172e-5p and miRNA472-3p in Arabidopsis thaliana by bioinformatics analysis. The results of dual luciferase reporter assay showed that miRNA172b-5p, miRNA172e-5p, and miRNA472-3p significantly reduced the related luciferase activity of reporter construct, which was decreased by 25.5%, 47.2% and 49.5%, respectively, compared with the negative control group in an Agrobacterium tumefaciensmediated in vitro assay (P<0.01). Results from Arabidopsis thaliana leaves injected transient expression in vivo assay showed that the over-expression level of miRNA172b-5p, miRNA172e-5p and miRNA472-3p was 178.9%, 123.6% and 37.6%, respectively. Results of qRT-PCR(real time quantitative reverse transcript polymerase chain reaction) showed that the expression of MSH6 was decreased by 20.3%, 22.7% and 38.2% in Arabidopsis thaliana leaves when exposed to 1.25, 2.5, 4.0 mg·L^-1 Cd stress for seven days, but the expression levels of miRNA172b-5p, miRNA172e-5p and miRNA472-3p were enhanced. There were negative relationships between these three miRNAs and MSH6gene (r=-0.995, P<0.01; r=-0.995, P<0.01; r=-0.984, P<0.05), indicating that miRNA172b-5p, miRNA172e-5p and miRNA472-3p were Cd responsive miRNAs and could directly target toMSH6 gene in Arabidopsis thaliana. Ourresults provide theoretical basis of miRNA for the study of Cd toxicological mechanism regulated by DNA mismatch repair (MMR) system.

Key words: burned area, soil dissolved organic carbon., soil organic carbon, soil microbial biomass carbon