TaWAKL8-2B, a wall-associated receptor-like kinase, mediates wheat rust resistance by linalool and ROS accumulation

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Wall-associated receptor kinases (WAKs) and WAK-likes (WAKLs) play pivotal roles in regulating plant immunity, through multiple downstream signaling components. However, knowledge of WAKs/WAKLs in wheat immune responses to rust diseases remain limited. In this study, we identified and characterized a wheat WAKL, TaWAKL8-2B, which is upregulated during wheat resistance to both Puccinia striiformis f. sp. tritici (Pst) and Puccinia triticina (Ptt), indicating its role in wheat resistance to these two rust fungi. Transgenic wheat plants overexpressing TaWAKL8-2B exhibited enhanced resistance to stripe rust and leaf rust, accompanied by increased reactive oxygen species (ROS) production and up-regulated defense-related gene expression. Whereas, knockout TaWAKL8-2B reduced resistance to Pst and Ptt with less ROS accumulation, highlighting its positive role in wheat resistance. RNA-seq analysis revealed that 33 genes encoding ROS-scavenging enzymes were upregulated in TaWAKL8-2B-KO plants, explaining the reduced ROS. KEGG analysis enriched the monoterpenoid pathway, particularly the linalool biosynthesis pathway, with linalool synthases significantly downregulated in TaWAKL8-2B-KO plants. Correspondingly, linalool synthase content and linalool content decreased in knockout plants. Collectively, our findings uncover a novel mechanism by which TaWAKL8-2B positively modulates wheat rust resistance through modulating linalool biosynthesis and peroxidase activity. These results enhance our understanding of TaWAKL8-2B mediated immune signaling and offer a promising gene for improving wheat broad-spectrum resistance to rust diseases.

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