Identification And Analysis Of Wheat WRKY Transcription Factors And Preliminary Study On Heat-Resistant Genes

Wheat is one of the three major food crops in China,but it is vulnerable to various stresses during its production.In particular,wheat production will severely reduce if grain filling stage suffered heat stress.As one of the largest family of transcription factors in plants,WRKY protein is involved in many signal transduction network pathways and regulates plant growth and development and various adversity defense processes.Based on the newly published wheat genome database,this study combined the commonly used bioinformatics analysis methods to identify and analyse the WRKY transcription factor family members,including their physical and physicochemical properties,phylogenetics,gene structure and conserved motifs,chromosome distribution and gene duplication,cis-acting elements,gene expression patterns,etc.At the same time,we also selected five TaWRKY genes that responded to heat stress and studied their expression profiles under different tissues and different stresses.Studying the WRKY family members in wheat and exploring key functional genes,heat-tolerant genes especially,will lay the foundation for improving the resistance of wheat and breeding resistant varieties.The main results of this study are as follows:1.In combination with BLAST,HMMER and searching online,290 wheat WRKY transcription factors members were identified in wheat genome.Meanwhile,they were named according to their subgroups.The physicochemical properties predictive analysis showed that the TaWRKY protein lengths ranged largely,the molecular weight and the isoelectric point were also significantly different.TaWRKY proteins are mostly hydrophilic unstable protein.TargetP subcellular localization prediction showed that TaWRKY protein was mainly localized in the nucleus,and there were also a small distribution of chloroplast,mitochondria and extracellular.KinasePhos predicted that the TaWRKY protein contains more MAPK phosphorylation sites.2.According to the results of phylogenetic analysis,WRKY TFs are divided into three subfamilies:I?39?,II?151?and III?100?.The subfamily II is further divided into five subgroups,IIa/IIb/IIc/IId and IIe.DNAMAN sequence analysis revealed that the conserved WRKYGQK has three variants,WRKYGRK,WTKYGQK and WRKYGKK,except common WRKYGKK and WRKYGEK types.The variant ZF type CX₅?Y?X₂₃HXH of was also found in TaWRKYIId-21.3.Gene structure analysis showed that the number of exons of TaWRKY gene ranged from 1 to 7.Different subfamilies varied greatly.The structure was similar in the same subfamily,while varied greatly in different groups.The results of protein conserved motifs analysis are consistent with the classification and phylogenetics.Almost all members contain motif 1 and motif 2,and motif 7 is the N-terminal conserved WRKY domain of I subfamily.In addition,there are some subfamilies.feature motif.4.The results of chromosomal localization indicated that the TaWRKY genes were distributed on 21 chromosomes of wheat.The number of genes on the 1D and 3D chromosomes was the highest,with 22 TaWRKY genes,accounting for 7.6%of the total,and 20 genes on 3A and 5D?6.9%?,there are 19 genes?6.6%?on 2A,3B and 5A;the least is4B chromosome,only 4 genes?1.4%?,followed by 6A/6B/6D chromosomes,each with 5genes?1.7%?.McscanX analysis found that 69 TaWRKY genes were tandeml duplication and 232 genes were segmental duplication.5.Using PlantCARE predicts the cis-acting element in the promoter region,and 115cis-acting elements are recognized witin 290 TaWRKY genes.In addition to transcription related elements,there are many growth-related,hormone-responsive,and stress-related cis acting elements.6.Gene expression pattern analysis showed that the temporal and spatial expression profiles of TaWRKYs were specific.Transcriptome data analysis indicated that several TaWRKY genes responded to heat stress and drought stress treatment.Five TaWRKY genes with significant response to heat stress were verified by qRT-PCR.The results showed that the expression of TaWRKY genes was tissue-specific and involved in heat stress at different growth stages.Furthermore,TaWRKY genes are also involved in various stress mechanisms such as ABA,PEG,NaCl,low temperature and so on.