WRKY domain-encoding genes of a crop legume chickpea (Cicer arietinum): comparative analysis withMedicago truncatulaWRKY family and characterization of group-III gene(s)

Abstract

The WRKY genes have been identified as important transcriptional modulators predominantly during the environmental stresses, but they also play critical role at various stages of plant life cycle. We report the identification of WRKY domain (WD)-encoding genes from galegoid clade legumes chickpea (Cicer arietinum L.) and barrel medic (Medicago truncatula). In total, 78 and 98 WD-encoding genes were found in chickpea and barrel medic, respectively. Comparative analysis suggests the presence of both conserved and unique WRKYs, and expansion of WRKY family in M. truncatula primarily by tandem duplication. Exclusively found in galegoid legumes, CaWRKY16 and its orthologues encode for a novel protein having a transmembrane and partial Exo70 domains flanking a group-III WD. Genomic region of galegoids, having CaWRKY16, is more dynamic when compared with millettioids. In onion cells, fused CaWRKY16-EYFP showed punctate fluorescent signals in cytoplasm. The chickpea WRKY group-III genes were further characterized for their transcript level modulation during pathogenic stress and treatments of abscisic acid, jasmonic acid, and salicylic acid (SA) by real-time PCR. Differential regulation of genes was observed during Ascochyta rabiei infection and SA treatment. Characterization of A. rabiei and SA inducible gene CaWRKY50 showed that it localizes to plant nucleus, binds to W-box, and have a C-terminal transactivation domain. Overexpression of CaWRKY50 in tobacco plants resulted in early flowering and senescence. The in-depth comparative account presented here for two legume WRKY genes will be of great utility in hastening functional characterization of crop legume WRKYs and will also help in characterization of Exo70Js.

WRKY transcription factors in legumes

“…Additionally, this method has also been previously used to detect the WRKY gene family in A. duranensis , A. ipaënsis , and G. max [ 18 , 29 ]. However, the WRKY gene family was identified in C. arietinum , L. japonicus , and M. truncatula using the similarity-based method [ 47 – 49 ]. In this study, we re-identified this gene family in the previously investigated genomes using the HMMs method.…”

Developing Climate-Resilient Chickpea Involving Physiological and Molecular Approaches With a Focus on Temperature and Drought Stresses

“…In chickpea, TFs for heat tolerance have been reported [CaMIPS1 and CaMIPS2 (Kaur et al, 2008b) and Ca_02170, Ca_16631, Ca_23016, Ca_09743, Ca_25602] (Agarwal et al, 2016). Recently, a genome-wide analysis of a WRKY TF gene model revealed the presence of 78 WRKY TFs evenly distributed across eight chromosomes in chickpea (Kumar et al, 2016). Car-WRKY TF is reportedly multi-stress responsive, playing a central role in stress signal transduction pathways (Konda et al, 2018).…”

Arabidopsis WRKY53, a Node of Multi-Layer Regulation in the Network of Senescence

“…Chinese cabbage Brassica rapa [38] CaWRKY50 chickpea Cicer arietinum [39] 11 members of the WRKY TF family (two WRKY42 genes, WRKY65, WRKY70, WRKY11, three WRKY33 genes, WRKY41, WRKY30, and an unknown WRKY domain-containing protein) At the beginning of this century, the first connections between WRKY factors and senescence have been established in Arabidopsis [27,28,51,52]. After the finalization of the Arabidopsis genome project, it became clear that 75 WRKY transcription factor genes exist, which can be categorized into three different groups based on the presence and number of their protein motifs and domains [51,53].…”