Molecular Characterization And Functions Of Wheat TaMIR1119/5086 And Transcription Factor Gene TaNF-YB6;1 Resistance To Abotic Stress

Abiotic stresses such as drought and salt stress are two important factors limiting crop growth and yield formation worldwide.To reveal the molecular mechanisms that plants response and resistance to drought and salt stress is of great significance for genetic improvement of stress resistance and production practices of crops.Based on the accumulation of laboratory works,the molecular characteristics and functions of TaMIR1119 and TaMIR5086 response to drought stress and the transcription factor gene TaNF-YB6;1 response to salt and drought stresses were studied.The main results are as follows:1.The initial sequence of TaMIR1119 176 nt long and the mature sequence is of 24 nt long,which ranging from 84 nt to 107 nt.It forms a stem-loop secondary structure through base-pairing of its own base complementary sequences.There are 6 target genes regulated by TaMIR1119,which are functionally classified into transcriptional regulation,RNA and biochemical metabolism,transport and oxidative stress.2.Under drought stress,TaMIR1119 and its tobacco homolog gene NtMIR1119 were both up-regulated in roots.The transgenic tobacco plants overexpressing TaMIR1119 showed significant growth characteristics under drought stress,improved plant morphology,increased dry matter quantity,enhanced photosynthetic carbon assimilation ability,and significantly improved antioxidant enzyme activities of SOD,POD and CAT compared to wild type(WT).It indicated that TaMIR1119 plays an important biological role in mediating plants resistance to drought stress by regulating the internal physiological and biochemical processes and enhancing the active oxygen scavenging capacity.3.The initial sequence of TaMIR5086 is 126 nt long and the mature sequence is of 21 nt long which located between 11 nt to 31 nt.The small molecule RNA has a secondary stem-loop structure formed by an inverted repeat region of its own sequences.There are six genes targeted by TaMIR5086,but their functions have not been verified.4.Under drought stress,TaMIR5086 was up-regulated in roots,and its expression pattern in the roots of the target genes was down-regulated.The expression of superoxide dismutase genes SOD1 and FeSOD,catalase genes CAT and CAT1;2,peroxidase genes POD4 and POD9 were significantly up-regulated under drought stress in transgenic tobacco plants overexpressing TaMIR5086.Those differentially expressed antioxidant enzyme genes are regulated by TaMIR5086 at the transcriptional level,which enhanced the abilities of ROS scavenging and drought resistance.In addition,the transgenic tobacco plants overexpressing TaMIR5086 reduced the water loss of plants by regulating the opening of stomata under drought stress,which reduced the damage caused by water deficiency and maintaining the normal growth of plants.5.The full length of TaNF-YB6;1 cDNA is 1018 bp,it contains an open reading frame of 411 bp,encoding 136 amino acids.Its molecular weight is 14.93 kD and an isoelectric point(pI)of 5.65.TaNF-YB6;1 is highly homologous to NF-YB transcription factors derived from plants such as pineapple,oil palm,barley,common wheat,wheat,rice and millet.6.Under drought and salt stress,the expression of TaNF-YB6;1 was up-regulated,and the transgenic tobacco plants of TaNF-YB6;1 showed obvious improvement in the morphology.The sense transgenic lines grow robustly and the individual plants enlarged,while the antisense transgenic lines grow slowly and the plants are short compared to WT.It indicated that TaNF-YB6;1 can mediate the function of plants against drought and salt stress,but its mechanisms of regulating plant resistance to osmotic stress needs further study.In summary,TaMIR1119 and TaMIR5086 and transcription factor gene TaNF-YB6;1 were all significantly response to drought stress,and transcription factor gene TaNF-YB6;1 significantly response to salinity too.Under drought stress,TaMIR1119 transgenic tobacco plants regulated plants to defense oxidative stress and enhance leaf photosynthetic carbon assimilation ability by targeting target genes which played an important biological function in mediating plant resistance to drought stress.Transgenic tobacco plants overexpressing TaMIR5086,maintained cell osmotic pressure by rapidly closing the stomata and increasing the content of osmotic adjustment substances in cells under drought stress,and enhancing the active oxygen scavenging ability of the transgenic plants by regulating expression level of antioxidant enzyme-related genes,which regulates the relative homeostasis of active oxygen in the plant,thereby improving the drought resistance of the plant.