Study On The Molecular Characteristics And Functions Of MIR9674a,MIR408 And MIR9780 Of Wheat Resistance To Abiotic Stresses

There exists various biotic and abiotic strsses in the growth cycle of wheat,among which the nutrition and salt stress are the most two important factors that affect the growth of crops.Plant miRNA plays an important role in plant resistance to abotic stresses which involved in many facts of the regulation of plant growing and developping.Based on the previous work of the laboratory,the molecular characteristics and functions resistance to abiotic stresses of TaMIR9674 a,TaMIR408 and TaMIR9780 were studied,the main results are as follows:1.TaMIR9674 a and TaMIR9780,two wheat miRNAs were identificated that response to salt stress.Their initial sequences are both 89 nt long and the mature sequences are both 20 nt long.But the region of matural sequence of TaMIR9674 a is located between 13 nt and 33 nt,while TaMIR9780 is between 68 nt and 88 nt.2.Under salt stress,the sence lines of the transgenic tobacco plants overexpressing TaMIR9674 a grew stronger and the fresh weight,leaf area,and the activities of cytoprotective enzymes increased than that of wild type,so as to the content of soluble sugar.While the membrane lipid peroxidation MDA and mesophyll conductivity decreased.But the anti transgenetic lines showed opposite results.The expression levels of cytoprotective enzyme-related genes,ABA receptor(PYL)related genes and SnRK2 family genes mediated ABA signal transduction in tobacco plants of TaMIR9674 a also changed: The expression of SOD1,FeSOD,Mn1 SOD,POD1.2,POD1.3,POD1.6 and POD2.1,CAT1.1,CAT1.2 and PYL8,PYL11 and SAPK1,SAPK3,SRK2E-9,SRK2A-4 genes were all up-regulated in sence lines,down-regulated in antisense lines of TaMIR9674 a transgenic plants.All those results indicated that TaMIR9674 a tansgenetic tobacco plant delayed the water evaporate through closing the stoma ripadly and increasing osmotic adjustment.What is more,the ability to clear the membrane lipid peroxidation MDA increased through cytoprotective enzyme genes and SnRK2 family genes mediated ABA signal transduction,which may decrease membrance injury,keep plant grow well under salt stress.3.Based on running an online tool,the genes putatively targeted by TaemiR408 were predicted,while three(TaCP?TaMP and TaBCP)are involved in biochemical metabolism,two(TaKRP and TaABP)in signal transduction and one(TaMP)in microtubule organization.The overexpression transgenic lines grew better than the wild type under low-Pi envoirment,and the phosphorus content and phosphorus accumulation increased,while under the salt stress,the osmotic regulator soluble sugar and proline content increased.This suggested that TaMIR408 may mediate plant resistance to low-Pi and salt stress by regulating the transcription of target genes.4.The phenotypic characteristics of transgenic tobacco plants overexpressing TaMIR9780 under salt stress were preliminarily identified.The results showed that there were no significant differences in growth and morphological characteristics between the transgenic lines and the wild type under normal culture conditions.However,under salt stress,the growth of the transgenic sence lines was slightly larger than that of the wild type,while the growth of the antisense lines was significantly weaker than that of the wild type.The molecular characteristics and functions resistance to stress of TaMIR9780 need to be further explored.In conclusion,TaMIR9674 a,TaMIR408 and TaMIR9780 all responded significantly to high salt stress.TaMIR9674 a transgenic lines can maintain cell osmotic pressure by rapidly closing stomata and increasing the content of osmotic regulators under high salt stress.At the same time,the scavenging ability of cytoprotective enzymes system improved and the accumulation of lipid peroxidation products such as MDA reduced,in which those physiological and biochemical processes reduced cell membrane damage.TaMIR408 responded to low phosphorus stress by improving plant phosphorus uptake and accumulation capacity of phosphorus under low phosphorus and high salt stress.Under high salt stress,the ability of osmotic regulation was improved by increasing the content of proline and soluble sugar,and the growth of transgenic lines overexpressing TaMIR408 was improved compared with wild type under the above two stresses.