Sharp eyespot, caused by the necrotrophic fungal pathogen Rhizoctonia cerealis, is a devastating disease of bread wheat (Triticum aestivum). However, the molecular mechanisms underlying wheat defense against Rhizoctonia cerealis are still largely unknown. In this study, we identified a novel cysteine-rich receptor-like kinase (CRK)-encoding gene, designated as TaCRK3, through comparative transcriptomic analysis, and investigated its defence role against Rhizoctonia cerealis. TaCRK3 transcriptional abundance was significantly elevated by R. cerealis and exogenous ethylene treatments. Silencing of TaCRK3 significantly compromised resistance to R. cerealis and repressed expression of an ethylene biosynthesis enzyme-encoding gene ACO2 and a subset of defence-associated genes in wheat, whose transcript levels are up-regulated by ethylene stimulus. TaCRK3 protein was localized at the plasma membrane in wheat. Noticeably, both the heterologously-expressing TaCRK3 protein and its partial peptide harboring two DUF26 domains could inhibit growth of R. cerealis mycelia. These results suggest that the TaCRK3 mediates wheat resistance to R. cerealis through direct-antifungal activity and heightening the expression of defence-associated genes in the ethylene signaling pathway, and that its DUF26 domains are required for the antifungal activity of TaCRK3. This study provides a promising gene for breeding wheat varieties with resistance to R. cerealis.

Fusarium head blight (FHB) and sharp eyespot are important diseases of the cereal plants, including bread wheat (Triticum aestivum) and barley. Both diseases are predominately caused by the pathogenic fungi, Fusarium graminearum and Rhizoctonia cerealis. The roles of the wheat-wall-associated kinases (WAKs) in defense against both F. graminearum and R. cerealis have remained largely unknown. This research reports the identification of TaWAK2A-800, a wheat WAK-coding gene located on chromosome 2A, and its functional roles in wheat resistance responses to FHB and sharp eyespot. TaWAK2A-800 transcript abundance was elevated by the early infection of R. cerealis and F. graminearum, or treatment with exogenous chitin. The gene transcript seemed to correspond to the resistance of wheat. Further functional analyses showed that silencing TaWAK2A-800 compromised the resistance of wheat to both FHB (F. graminearum) and sharp eyespot (R. cerealis). Moreover, the silencing reduced the expression levels of six defense-related genes, including the chitin-triggering immune pathway-marker genes, TaCERK1, TaRLCK1B, and TaMPK3. Summarily, TaWAK2A-800 participates positively in the resistance responses to both F. graminearum and R. cerealis, possibly through a chitin-induced pathway in wheat. TaWAK2A-800 will be useful for breeding wheat varieties with resistance to both FHB and sharp eyespot.