The WRKY TF family is one of the largest transcription factor (TF) families in higher plants with over 100 members in the Arabidopsis genome (Ulker et al., 2004). A number of studies have demonstrated that the WRKY transcription factors play critical roles in response to biotic and abiotic stress. In spite of the strong conservation of their DNA-binding domain, the overall structures of WRKY proteins are highly divergent and can be categorized into distinct groups, which might reflect their different functions.

The WRKY proteins can induce or repress the expression of their downstream genes by specifically binding to W-box [TGACC (A/T)] at their promoter sites and eventually activate their stress responses. One of the distinguishing features of the WRKY TFs is the presence of highly conserved WRKY domain. The conserved WRKY domain is composed of approximately 60 amino acid residues with a highly conserved heptapeptides, WRKYGQK, at the N-terminus, and a novel zinc finger motif C2H2 (CX4–5CX22–23HXH) or C2HC (CX7CX23HXC) at their C-terminus]. On the basis of the characteristics of WRKY domain and zinc-finger-like motif, the WRKY TFs can be grouped into three major Groups (I, II, and III). The Group II WRKY members are further divided into five subgroups (IIa-IIe) according to their evolutionary divergence. The Group I members contain two WRKY domains with C2H2 zinc-finger-like motifs. The Group II members contain a single WRKY domain including a C2H2 zinc-finger-like motif. The WRKY TFs containing a single WRKY domain with a C2HC zinc-finger-like motif belong to the Group III (Hu et al., 2021).

About 125 WRKY genes have been identified in maize (Hu et al., 2021). On the basis of features described above, the ZmWRKY proteins in maizehave been divided into three main groups (Groups I, II and III) and the Group II was further classified into five subgroups. Most of Zthe mWRKY genes displayed differential expression patterns at different developmental stages and by quantitative real-time PCR analysis, twenty-one ZmWRKY genes were confirmed to respond to two different abiotic stress treatments, suggesting their potential roles in various abiotic stress responses (Hu et al., 2021. Overexpression of the ZmWRKY65 transcription factor from maize confers stress resistances in transgenic Arabidopsis (Huo et al., 2021). ZmWRKY40 and ZmWRKY106 were also identified to enhance the tolerances to drought and high-temperature (Wang et al., 2018, Wang et al., 2018).

Last updated June 2023 by John Gray

References:

Ulker B, Somssich IE. WRKY transcription factors: from DNA binding towards biological function. Curr Opin Plant Biol. 2004 Oct;7(5):491-8. doi: 10.1016/j.pbi.2004.07.012. PMID: 15337090.

Hu W, Ren Q, Chen Y, Xu G, Qian Y. Genome-wide identification and analysis of WRKY gene family in maize provide insights into regulatory network in response to abiotic stresses. BMC Plant Biol. 2021 Sep 20;21(1):427. doi: 10.1186/s12870-021-03206-z. PMID: 34544366; PMCID: PMC8451115.

Huo T, Wang CT, Yu TF, Wang DM, Li M, Zhao D, Li XT, Fu JD, Xu ZS, Song XY. Overexpression of ZmWRKY65 transcription factor from maize confers stress resistances in transgenic Arabidopsis. Sci Rep. 2021 Feb 17;11(1):4024. doi: 10.1038/s41598-021-83440-5. PMID: 33597656; PMCID: PMC7889854.

Wang CT, Ru JN, Liu YW, Li M, Zhao D, Yang JF, Fu JD, Xu ZS. Maize WRKY Transcription Factor ZmWRKY106 Confers Drought and Heat Tolerance in Transgenic Plants. Int J Mol Sci. 2018 Oct 6;19(10):3046. doi: 10.3390/ijms19103046. PMID: 30301220; PMCID: PMC6213049.

Wang CT, Ru JN, Liu YW, Yang JF, Li M, Xu ZS, Fu JD. The Maize WRKY Transcription Factor ZmWRKY40 Confers Drought Resistance in Transgenic Arabidopsis. Int J Mol Sci. 2018 Aug 30;19(9):2580. doi: 10.3390/ijms19092580. PMID: 30200246; PMCID: PMC6164628.