Comparative Analysis of WRKY Genes Potentially Involved in Salt Stress Responses in Triticum turgidum L. ssp. durum

Abstract

WRKY transcription factors are involved in multiple aspects of plant growth, development and responses to biotic stresses. Although they have been found to play roles in regulating plant responses to environmental stresses, these roles still need to be explored, especially those pertaining to crops. Durum wheat is the second most widely produced cereal in the world. Complex, large and unsequenced genomes, in addition to a lack of genomic resources, hinder the molecular characterization of tolerance mechanisms. This paper describes the isolation and characterization of five TdWRKY genes from durum wheat (Triticum turgidum L. ssp. durum). A PCR-based screening of a T. turgidum BAC genomic library using primers within the conserved region of WRKY genes resulted in the isolation of five BAC clones. Following sequencing fully the five BACs, fine annotation through Triannot pipeline revealed 74.6% of the entire sequences as transposable elements and a 3.2% gene content with genes organized as islands within oceans of TEs. Each BAC clone harbored a TdWRKY gene. The study showed a very extensive conservation of genomic structure between TdWRKYs and their orthologs from Brachypodium, barley, and T. aestivum. The structural features of TdWRKY proteins suggested that they are novel members of the WRKY family in durum wheat. TdWRKY1/2/4, TdWRKY3, and TdWRKY5 belong to the group Ia, IIa, and IIc, respectively. Enrichment of cis-regulatory elements related to stress responses in the promoters of some TdWRKY genes indicated their potential roles in mediating plant responses to a wide variety of environmental stresses. TdWRKY genes displayed different expression patterns in response to salt stress that distinguishes two durum wheat genotypes with contrasting salt stress tolerance phenotypes. TdWRKY genes tended to react earlier with a down-regulation in sensitive genotype leaves and with an up-regulation in tolerant genotype leaves. The TdWRKY transcripts levels in roots increased in tolerant genotype compared to sensitive genotype. The present results indicate that these genes might play some functional role in the salt tolerance in durum wheat.

Transcriptome analysis reveals gene responses to herbicide, tribenuron methyl, in Brassica napus L. during seed germination

“…For example, WRKY is from a group of transcription factors that play a vital role in stress tolerance. Their expression was higher in Rt than in St, and similar results were obtained by other researchers who found contrasting expression pattern of genes like WRKY in resistant and susceptible genotypes [ 49 , 50 ]. These genes do not work independently, as shown in the metabolic pathway (Fig.…”

Structural and functional dissection of differentially expressed tomato WRKY transcripts in host defense response against the vascular wilt pathogen (Fusarium oxysporum f. sp. lycopersici)

“…The inconsistencies observed in the experimental results well suggested the need for a rather stringent conformational structure for high affinity binding and further in depth studies for the structural determination of the protein complexed with DNA and sequence specific DNA recognition by WRKY domains. However, it has been reported that WRKY TFs can bind to other functional cis -acting elements [ 143 ]. The PLACE server revealed the core elements that could be involved in binding with WRKY TFs including the TGACT(WBOXHVISO1; SURE (sugar responsive) is a cis element in plant sugar signaling, TTGAC (WBOXATNPR1; salicylic acid induced WRKY DNA binding proteins [ 144 ] TGAC (WRKY71OS; that constitutes the defense signaling of WRKY proteins and found their role in pathogenesis.…”

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