TaWRKY24 Positively Regulates Wheat Resistance to Puccinia striiformis f. sp. Tritici via Modulation of Defense Signaling and Reactive Oxygen Species Accumulation.

Abstract

Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), remains a major threat to global wheat production, which necessitates a better understanding of the molecular mechanisms underlying resistance. WRKY transcription factors are pivotal regulators of plant immunity; however, their specific functions in the wheat-Pst pathosystem remain poorly characterized. In this study, we identified and functionally characterized a WRKY transcription factor gene, TaWRKY24, in wheat. Expression profiling revealed that TaWRKY24 was continuously induced upon Pst inoculation. Subcellular localization assays demonstrated that the TaWRKY24 protein is predominantly localized to the nucleus. Functional analyses indicated that transient overexpression of TaWRKY24 significantly enhanced wheat resistance to Pst, whereas virus-induced gene silencing (VIGS) compromised wheat resistance to Pst. Histological observations revealed that TaWRKY24 promotes reactive oxygen species (ROS) accumulation at early infection sites and restricts fungal hyphal expansion. To further explore the underlying mechanism, combined transcriptomic and qRT-PCR analyses showed that silencing TaWRKY24 resulted in significant downregulation of key genes involved in MAPK signaling (MKK4/5, WRKY33), glutathione metabolism (GSS), and phenylpropanoid biosynthesis (PAL). In addition, yeast one-hybrid and dual-luciferase reporter assays demonstrated that TaWRKY24 directly binds to and activates the promoters of PAL- and MAPK-related genes. Collectively, our findings suggest that TaWRKY24 positively regulates wheat resistance to Pst, likely through the modulation of MAPK-mediated immune signaling, ROS homeostasis, and defense-related metabolic pathways. This study provides novel insights into the regulatory functions of WRKY transcription factors in wheat innate immunity.