The Analysis Of Drought-resistant Mes-miR162a And Its Target

MicroRNAs(miRNAs) are small noncoding RNA of20-22nt nucleotides length widely existing in the organisms which play a important role in gene expression. By mRNA cleavage or translation repression, miRNAs regulate the expression of endogenous genes and involve in various kinds of regulation pathways in the organisms. Recently researchs show that miRNA could cause increased drought tolerance by regulating the expression of the genes which respond to the drought stress. As a typical tropical crop, cassava would be damaged in drought stress. So the study of drought related miRNAs and their targets would provides a new rationale and mentality for the genetic improvement of drought tolerance in cassava.MemiR-162a and its target MeGSTU7gene were singled out as the object of study and two cassava species SC124and Arg7were used as experiment material. Drought stress was set and q-PCR and RACE were performed for researching the expression of MemiR-162a and MeGSTU7under different drought stress and the cleavage sites were find out. MeGSTU7in60cassava species was sequenced for the research of the natural variation of MeGSTU7. The results were as follows:1. The result of the q-PCR showed that MeGSTU7were over-active under drought stress and MemiR-162a were under-active. Presented a coaction relation between MemiR-162a and MeGSTU7.2. The coaction relation between MemiR-162a and MeGSTU7were further confirmed by5'RACE. The cleavage sites in MeGSTU7sheared by MemiR-162a were ensured which existed in13bp within binding domain and-50bp in the catchent area of the binding domain.3. Two Indel and twenty-three SNP exist in gene region of MeGSTU7. The A/G mutation type occupies the major, followed by C/T mutation type.11replacement changes existed in CDS region, among which5located in conserved domain. The exon of MeGSTU7contains28haplotype, among which4haplotype divided into2types are the major. Molecular evolution showed that the gene at the end of coding region suffered the positive selection effect significantly. By Q+K+MLM mixed linear model, one Indel and2SNP were significantly associated with the anti-drought coefficiency of fresh weight of aerial part and excellent allelic variations were selected.In conclusion, this paper verified the coaction relation of the expression under drought stress between MemiR-162a and MeGSTU7. Ensured the cleavage sites in MeGSTU7sheared by MemiR-162a and analysised the correlation of genotypic variation of MeGSTU7with drought stress. This paper lay the foundation for the further research in the molecular mechanism that MemiR-162a respond to drought stress and the function of MeGSTU7. And provides a new rationale and mentality for the genetic improvement of drought tolerance in cassava.