Wheat COP9 Subunit 5 Gene Is Negatively Involved in Host Resistance to Leaf Rust

The COP9 signalosome (CSN), a conserved multi protein complex consisting of eight subunits that were initially defined as a negative regulator of photomorphogenesis in plants, has recently been found to be a common host target protein of diverse pathogens in Arabidopsis. Here we identified and cloned the wheat COP9 signalosome subunit 5 gene (TaCSN5) and demonstrate its involvement in wheat pathogen response. Wheat (Triticum aestivum L.) has three homologs of TaCSN5 located on the long arm of group 2 chromosomes. TaCSN5 expression time course study revealed that in wheat cultivar Alpowa TaCSN5 expression was up-regulated after challenge with Puccinia triticina (leaf rust). Furthermore, TaCSN5 expression increase was detected at 5 days post inoculation, suggesting the role of TaCSN5 during wheat-leaf rust pathogen interaction was likely involved in host susceptibility. Down-regulation of all three TaCSN5 homologs via VIGS resulted in enhanced resistance to leaf rust. EMS derived mutations in TaCSN5-2A and TaCSN5-2D enhanced resistance to leaf rust. Disease assays conducted on Chinese Spring group 2 nulli-tetra lines suggested that TaCSN5-2A and TaCSN5-2D functionally compensate for each other related to leaf rust susceptibility. Collectively, the data indicate that wheat COP9 subunit 5 acts as a negative regulator of wheat disease resistance.