ZmWRKY79 positively regulates maize phytoalexin biosynthetic gene expression and is involved in stress response

Abstract

Maize (Zea mays) accumulates maize terpenoid phytoalexins (MTPs), kauralexins and zealexins in response to various elicitations. Although the key biosynthetic genes for these have been characterized, the regulatory mechanism remains unclear. Through co-correlation analysis, a transcription factor (TF), ZmWRKY79, was identified as highly correlated with expression of MTP biosynthetic genes. Gene expression analysis indicated that ZmWRKY79 was induced by Fusarium graminearum infection, phytohormone treatment, and multiple stresses. Overexpression of ZmWRKY79 in maize protoplasts increased expression of genes involved in MTP biosynthesis, jasmonic acid and ethylene pathways, and scavenging of reactive oxygen species (ROS). Subsequent transient RNAi in maize protoplast compromised the induction of MTP biosynthetic genes by jasmonic acid and ethylene combined treatment. Such regulation was further demonstrated to be dependent on a W-box or WLE cis-element. Transient overexpression of ZmWRKY79 in tobacco conferred resistance against Rhizoctonia solani infection through reducing ROS production. Our results indicate that MTP biosynthesis is regulated by the common transcription factor ZmWRKY79, which plays a broad role as a potential master regulator in stress response through involvement in phytohormone metabolism or signaling and ROS scavenging.

Commonly and Specifically Activated Defense Responses in Maize Disease Lesion Mimic Mutants Revealed by Integrated Transcriptomics and Metabolomics Analysis

“…In our research, 18 WRKY and 5 MYB TFs were upregulated in all three Les mutants (Supplementary Table 10), implying their contributions to the enhanced resistance. Interestingly, WRKY79 (Zm00001d020137), which was previously shown to positively regulate zealexins and kauralexins biosynthesis (Fu et al, 2018), was upregulated in all Les mutants (Supplementary Table 10), consistent with the upregulation of the terpenoid biosynthetic genes (Figure 7 and Supplementary Table 17). Previous studies also indicated that a series of MYB TFs were involved in the transcriptional regulation of lignin and flavonoid biosynthesis (Zhao and Dixon, 2011;Geng et al, 2020;Wang et al, 2020); some of the MYB TFs identified in this study may be potentially involved in lignin and flavonoid biosynthesis in maize.…”

Transcriptional Factors Regulate Plant Stress Responses Through Mediating Secondary Metabolism

“…Moreover, the maize TF ZmWRKY79 regulates the biosynthesis of phytoalexins in response to various stress conditions. Expression of several genes related to zealexins and kauralexins biosynthesis was elevated in the ZmWRKY79 transient overexpression maize protoplasts [69]. TcWRKY1 has also been studied to play roles in taxol biosynthesis in Taxus chinenesis to upregulate dbat gene, resulting in higher accumulation of taxol [70].…”

Current understanding of maize and rice defense against insect herbivores

“…These compounds also show significant O. nubilalis antifeedant activity (Schmelz et al., 2011). Maize ZmWRKY79 physically binds to the W-boxes or WLE cis-elements in the promoters of terpenoid phytoalexin biosynthetic genes ( An2 and ZmTPS6 ) in maize, regulating the expression of these genes (Fu et al., 2018). An AP2/ERF type transcription factor EREB58 (GRMZM2G381441) has been shown to bind the promoter of TPS10 and mediate jasmonate-induced biosynthesis of sesquiterpenes (Li et al., 2015b).…”