| Members of the sucrose non-ferment-1-related protein kinase 2(SnRK2)family play an important role in plant response and resistance to abiotic stresses by mediating signaling transduction.In this study,the molecular characteristics,expression patterns of TaSnRK2.4 in response to salinity and drought stress,and its regulation on plant response to salt and drought stresses were investigated using wheat transgenic lines.The main results are as follows:The cDNA length of TaSnRK2.4 is 1648 bp,containing a 1092 bp of open reading frame(ORF)and encoding a 363 amino acid polypeptide.Themolecular weight of TaSnRK2.4 protein is 42.09 kD with an isoelectric point(pI)of 5.77.Protein domain prediction analysis showed that TaSnRK2.4 protein contains the conservative Ser/Thr kinase domain.At the nucleotide level,TaSnRK2.4 was highly similar to the homologous genes in species of H.vulgare,T.elongatum,S.viridis.Z.mays,other plant species,indicating that these genes may have similar evolutionary pathways.The results of subcellular localization showed that the reporter signal of TaSnRK2.4-GFP fusion protein was confined in the nucleus of tobacco leaf epidermis.Yeast two-hybrid analysis confirmed that there was an interaction between the TaSnRK2.4 protein and a phosphatase referred to as TaPP2C01.Gene expression analysis showed that TaSnRK2.4 had a typical salt and drought stress-induced expression pattern,compared with the expression level under normal growth conditions,the expression level of this gene was increased with the treatment procession within 9 h under salt treatment.It wasthen gradually decreased following the osmotic stresses.The genetic transformation analysis showed that the growth of sense and antisense TaSnRK2.4 transgenic tobacco and wheat lines was significantly changed under salt and drought treatment compared with the wild type control(wild typw,WT).Among these,the growth of the sense line(Sen 1)was enhanced,the fresh weight,dry weight and leaf area were increased,and the root development was improved;in contrast,the plant growth of Anti 1 was worse,the fresh weight,dry weight and leaf were lower,and the root development was more alleviated than those of the control.The stomatal closure of Sen 1 and Anti 1 under drought was faster and slower than that of the control,respectively.Under salt and drought treatment,compared with the control,the photosynthetic capacity,soluble protein and soluble sugar content in the sense transgenic line were improved,the activities of cell protective enzymes SOD,CAT and POD were enhanced,the content of membrane lipid peroxidation product MDA was decreased,and the accumulation of H2O2 and O2-in leaves was significantly reduced.The expression analysis of cell protective enzyme genes in TaSnRK2.4 tobacco transgenic lines under salt and drought treatment showed modified expression on following family members,including NtFeSOD,NtMnSOD1,NtCAT1,NtCAT1;2,NtPOD1;1,NtPOD1;2,and NtPOD1;6 under salt stress;and NtSOD 2,NtFeSOD,NtMnSOD1,NtCAT 1,NtCAT1;1,NtCAT 3,NtPOD 1;1,NtPOD 1;3,and NtPOD 2;1 under drought stress.These genes were upregulated in expression in lines overexpressing TaSnRK2.4 and downregulated in expression in lines with knockdown of the target kinase gene.The results showed that TaSnRK2.4 enhanced the ability of active oxygen scavenging under osmotic stress by regulating the transcription of genes encoding cytoprotective enzymes.In summary,this study confirmed that TaSnRK2.4 is a member of the wheat SnRK2 family that responds significantly to salt and drought stress.TaSnRK2.4 plays a positive regulatory role in mediating plant tolerance tosalt and drought stresses. |
