The Function Of TaWRKY46 And TaHD2-1 In Mediating Acclimation Of Plants To Salt Stress

Worldwide salt stress is a serious threat to food security.The results showed that WRKY transcription factors and HDAC family play important roles in responding to salt stress.In this study,the biological functions of a wheat WRKY family gene TaWRKY46 and a wheat HDAC family gene TaHD2-1 mediating plant responses to salt stress were studied.The main results are as follows:TaWRKY46 contains one WRKY domain and one C2HC zinc finger domain,which belongs to WRKY Ⅲ type transcription factor.The experiment indicated that TaWRKY46 targets onto nucleus at subcellular level.Using the culture methods of vermiculite-based and Murashige&Skoog(MS)hydroponicsolution,the phenotype of wild type(WT)and transgenic lines(OE)under salt stress treatment was investigated.OE1 and OE5,two OE lines overexpressin TaWRKY46,displayed increased growth vigor and leaf area of plants,together with enhanced plant fresh weight and contents of soluble sugar and proteins upon salt stress with respect to WT.Assays on the activities of SOD,POD,and CAT,the enzymes functional as cellular protection,revealed the higher activities of them in OE lines than those in WT plants.RT-PCR analysis indicated the expression levels of part protection enzymes mentioned above are higher in the OE1 and OE5 roots that WT under salt stress treatment.Further histochemical staining study via nitroblue tetrazolium(NBT)and diaminobenzidine(DAB)dyeing methods revealed that the accumulative amounts of H2O2 and O2-· are lower in the OE plants than WT plants.The expression analysis revealed that the ABA receptor gene PYL8 and a suite of SnRK2 family genes are upregulated in expression in the OE plants.Observation on stomata movement suggested that the OE plants possess enlarged stomata aperture and increased closure rate upon salt stress compared with the WT plants.Using yeast-two hybridization assay,TaWRKY46 was identified to be interacted with TaSAP1-1,a stress-related protein in T.aestivum.Therefore,besides osmotic regulation,TaWRKY46 mediates plant salt tolerance through the two levels,namely,improving protection enzyme activity and regulating protective enzyme gene expression that further adjust ABA signaling pathway,stomata aperture and closing rate as well as protein interaction.Our study enriches the knowledge as to wheat plants cope with salt stress and provides theoretical guidance for breeding salt tolerant cultivars of crops.A HDAC gene was identified in our previous microarray analysis of wheat root response to low phosphorus.It’s accession number is EF368365,and the ORF of this gene is 933 bp long,encoding a 310 amino acid-polypeptide.The MW of the encoded protein is 34.91 kD with pI of 4.57,and harbors a zinc finger domain(aa285 to aa307).The phylogenetic tree and multiple sequence alignment analysis showed that the gene belongs to the group 1 type of histone deacetylase HD2 family,and then was named TaHD2-1.By subcellular localization analysis,TaHD2-1 was found located in the nucleus.Analysis of expression pattern showed that TaHD2-1 was up regulated under salt and drought stress.Using RT-PCR and DNA recombination technology,we constructed the recombinant plasmid of overexpression vector of TaHD2-1,and established the OE plants by Agrobacterium mediated method.Phenotype identification showed that the OE plants had obvious growth advantage over the WT under salt stress.The molecular mechanism of TaHD2-1 in response to salt stress needs to be further study.