Abstract
Wheat leaf rust, caused by the biotrophic fungus Puccinia triticina (Pt), is one of the most destructive diseases threatening global wheat production. Lysin motif (LysM)-containing receptors play central roles in plant recognition of fungal chitin and activation of pattern-triggered immunity (PTI), but the function of the LysM receptor-like kinase TaLYK5 in wheat resistance to leaf rust remains largely unknown. Here, we show that TaLYK5 lacks conserved kinase motifs essential for catalytic activity and is predicted to be a pseudokinase, suggesting that it may function through a co-receptor to transmit chitin signals. The transcript levels of TaLYK5 were rapidly and persistently upregulated upon Pt infection and chitin treatment in wheat. Transient expression of TaLYK5-6A in Nicotiana benthamiana significantly enhanced chitin-induced callose deposition. Transient silencing of TaLYK5 in wheat compromised resistance to Pt, with reduced H₂O₂ accumulation and increased fungal colonization. Importantly, stable overexpression of TaLYK5-6A in transgenic wheat lines conferred enhanced resistance to Pt, as shown by significantly fewer uredia and lower fungal biomass. Furthermore, overexpression of TaLYK5-6A enhanced chitin-induced callose deposition and expression of PTI marker genes. Collectively, these results demonstrate that TaLYK5 positively regulates wheat resistance to leaf rust, and this regulation is associated with chitin-triggered PTI, highlighting its potential as a candidate gene for improving leaf rust resistance in wheat.