The Rice(Oryza Sativa L.) Response To The Combined Stress Of High Temperature And Drought

High temperature and drought are especially considered as key stress factors with high potential impact on crop yield in numerous abiotic stresses.High temperature is often accompanied with drought which produces the combined stress to crops.The combined stress will usually appear synergistic effect or antagonistic effect compared with the single stress.However,the molecular mechanism of rice response to the combined stress of high temperature and drought has not been understood.This study used Nagina22-19379(N22)as material to study the physiological and molecular mechanisms of rice response to the combined stress of high temperature and drought.The following is the main results of this paper:(1)The heat-resistant rice variety N22 was used as the material for the combined stress of high temperature and drought for 3,5,7,9,14 day respectively,to study the dynamic change of protective enzyme activity,malondialdehyde,Soluble sugar,soluble protein,free proline and hormones in rice flag leaf.The results showed: under the combined stress of high temperature and drought,the activity of protective enzyme SOD and POD in rice leaves decreased,and the antioxidant capacity of rice was decreased significantly;The content of IAA,ZT and GA decreased ABA and SA content increased;The content of free proline,soluble protein and soluble sugar decreased while MDA content increased.(2)Two small RNA libraries were constructed from normal control group(CK)and heat-drought combine stress(FH)of Nagina22(N22),The libraries were submitted to high-throughput sequencing,494 conserved miRNAs,1458 new miRNAs,and 48 differentially expressed miRNA were identified.(3)The 1087 target genes of differentially expressed miRNA were predicted using bioinformatics analys,and the function of GO and Pathway of the target genes were enriched.At last,five miRNA and their target genes(osa-miR414/ LOC_Os02g41680、osa-miR394/ LOC_Os02g54140 、 osa-miR397b/ LOC_Os08g35210 、 osa-miR5078/ LOC_Os03g40540、osa-miR396d/ LOC_Os02g53690)were analyzed by qPCR.The results of qPCR analysis in ten miRNAs were consistent with sequencing.At same time,the expression of miRNA was negatively regulated that of target gene.In this study,the physiological and biochemical indexes of rice were tested under the combined stress of high temperature and drought.miRNA of the combined stress of high temperature and drought response were obtained by high-throughput sequencing.The target genes were predicted by bioinformatics,and the functional annotation and pathway enrichment analysis of target genes were carried out.Finally,five significant different miRNA and their target genes were verified by real-time PCR,and the results were consistent with the sequencing and negatively regulated with mRNA.