RNAi‐mediated stable silencing of TaCSN5 confers broad‐spectrum resistance to Puccinia striiformis f. sp. tritici

The constitutive photomorphogenesis 9 (COP9) signalosome (CSN) is a versatile regulator of plant growth, development, and response to diverse pathogens. However, little research has been done to understand the function of those CSN genes in broad‐spectrum resistance to pathogens. In this study, we found that the transcript levels of wheat TaCSN5 were induced in response to inoculation with Puccinia striiformis f. sp. tritici (Pst) and treatment with salicylic acid (SA). Overexpression of TaCSN5 in Arabidopsis resulted in increased susceptibility to Pseudomonas syringae pv. tomato DC3000 infection accompanied by down‐regulation of AtPR1 expression. Overexpression of TaCSN5 in wheat lines significantly increased susceptibility to Pst accompanied by decreased SA accumulation, whereas TaCSN5‐RNAi wheat lines exhibited opposite trends. Moreover, we found that TaCSN5 negatively regulated TaG3NPR1 genes involved in the SA signalling pathway. In addition, TaCSN5‐RNAi lines showed increased resistance to multiple races of Pst. Taken together, we demonstrate that TaCSN5 contributes to negative regulation of wheat resistance to Pst in an SA‐dependent manner.