Studies On Characterization And Functions Of Small RNA Molecules TaMIR5062/1139 And Kinase Genes TaMAPKK1/MAPKK;A In Wheat

Abiotic stresses such as salinity,drought and nutrient deficiency have important effects on plant growth and development.Salt and drought are important factors in inducing hyperosmotic stress,acting as common adversities in affecting crop yield and quality.Plant growth and development are also affected by phosphorus deficiency.In this study,the small RNA molecules TaMIR5062,TaMIR1139 and mitogen-activated protein kinase genes TaMAPKK1 and TaMAPKKK were subjected to analyses for the molecular characteristics and functions in mediating plant stress tolerance.The main results are as follows:1.The precursor sequence length of TaMIR5062 is 158 nt with a mature sequence of 23 nt.This miRNA member was shown to be obviously response to high-salt and drought stresses.Using DNA recombination technology,the tobacco transgenic lines with positive and antisense expression of TaMIR5062 were established.Moreover,the plant morphology,protective enzyme activities,water loss rate and conductivity as well as the expression paterns of related genes in transgenic lines and wild type(WT)plants were analyzed under high-salt and drought treatments.Compared with WT,the transgenic lines with overexpression of TaMIR5062 displayed improved morphology and water retention rate and increased the activities of antioxidant enzymes.Some genes related to cytoprotective enzymes,such as CAT,SOD and POD,were up-regulated in expression in the transgenic plants relative to those in WT plants.These results showed that TaMIR5062 could improve the ability of plants to resist hyperosmotic stress by regulating the activities of specific protective enzymes.2.The precursor sequence length of TaMIR1139 is 216 nt with a mature sequence of 22 nt.TaMIR1139 was shown to be up-regulated upon low P treatment and whose induced expression levels were down-regulated following the P normal recovery treatment.On the contrary,the expression levels of the TaMIR1139 target genes displayed revese expression patterns upon P starvation stress as well as following the P recovery.These expression results suggested that the target genes are regulated by this miRNA member at posttranscriptional level.Compared with WT,the tobacco lines with TaMIR1139 overexpression were shown to be improved on plant growth and P accumulative amounts P deficiency conditions.A phosphate transporter(PT)gene referred to NtPT was significantly up-regulated in the TaMIR1139 overexpression lines,which contributed to the plant resistance to low P stress in the transgenic lines.3.The wheat mitogen-activated protein kinase genes TaMAPKK1 and TaMAPKKK;A contained full-length cDNA of 1279 bp and 1247 bp that encode polypeptides of 355 aa and 251 AA,respectively.Both of them displayed upregulated expression patterns under high-salt and drought treatments,especially under the high-salt stress condition.The binary expression cassettes fused the open reading frames(ORFs)of TaMAPKK1 and TaMAPKKK;A were constructed by using DNA recombination and genetic transformation approaches.Protein localized detection analysis showed that TaMAPKK1 was localized in cytoplasm whereas TaMAPKKK;A was localized in cell wall and apoplast.In conclusion,TaMIR5062 plays an important biological role in mediating plant resistance to hypertonic stress by improving plant growth,protective enzyme activity and leaf water-holding capacity under hypertonic stress;TaMIR1139 regulates phosphorus transporter genes after transcription to enhance plant resistance to low phosphorus stress;TaMAPKK1 and TaMAPKKK;A respond to high salt and drought stress.TaMAPKK1 was located in cytoplasm,TaMAPKKK;A was located in cell wall and intercellular space.