Abstract
WRKY transcription factors comprise one of the largest gene families and serve as key regulators of plant defenses against herbivore attack. However, studies related to the roles of WRKY genes in response to herbivory are limited in maize. In this study, a total of 128 putative maize WRKY genes (ZmWRKYs) were identified from the new maize genome (v4). These genes were divided into seven subgroups (groups I, IIa–e, and III) based on phylogenomic analysis, with distinct motif compositions in each subgroup. Syntenic analysis revealed that 72 (56.3%) of the genes were derived from either segmental or tandem duplication events (69 and 3, respectively), suggesting a pivotal role of segmental duplication in the expansion of the ZmWRKY family. Importantly, transcriptional regulation prediction showed that six key WRKY genes contribute to four major defense-related pathways: L-phenylalanine biosynthesis II and flavonoid, benzoxazinoid, and jasmonic acid (JA) biosynthesis. These key WRKY genes were strongly induced in commercial maize (Jingke968) infested with the Asian corn borer, Ostrinia furnacalis, for 0, 2, 4, 12 and 24 h in the field, and their expression levels were highly correlated with predicted target genes, suggesting that these genes have important functions in the response to O. furnacalis. Our results provide a comprehensive understanding of the WRKY gene family based on the new assembly of the maize genome and lay the foundation for further studies into functional characteristics of ZmWRKY genes in commercial maize defenses against O. furnacalis in the field.
Highlights
Plants have evolved sophisticated inducible defense mechanisms to cope with herbivore attack at different stages of growth, involving changes at the molecular, cellular, biochemical, and physiological levels [1,2,3]
We investigated the expression of these key WRKY transcription factors (TFs) and their target genes in response to O. furnacalis feeding in more detail
The results showed that all key WRKY genes except for ZmWRKY71 and ZmWRKY79 were significantly upregulated during O. furnacalis feeding, and that ZmWRKY42 was strongly induced at all four time points postinfestation (Figure S1)
Summary
Plants have evolved sophisticated inducible defense mechanisms to cope with herbivore attack at different stages of growth, involving changes at the molecular, cellular, biochemical, and physiological levels [1,2,3]. These responses are generally controlled by several key genes encoding transcription activators and repressors that regulate downstream defense-related signal transduction pathways [4]. Extensive research has shown that transcription factors (TFs) are central regulators of gene expression; they play vital regulatory roles in plant defenses against herbivores [5,6,7].
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