Puccinia triticina effector Pt-1234 modulates wheat immunity by targeting transcription factor TaNAC069 via its C subdomain

The NAC (NAM, ATAF1/2, and CUC2) is a defense-associated transcription factor (TF) family that positively regulates defense responses to pathogen infection. TaNAC069 positively regulates resistance in wheat to Puccinia triticina (Pt). However, the molecular mechanism of its interaction with a Pt effector is not clear. We found that Pt effector Pt-1234 interacts with TaNAC069 to subvert host immunity during Pt infection. Quantitative real-time PCR analysis showed that expression of Pt-1234 was significantly up-regulated during the early stage of Pt infection. Protein-mediated cell death assays in wheat showed that the Pt-1234 protein was unable to induce cell death in wheat near-isogenic lines carrying different leaf rust resistance genes, whereas it suppressed BAX-induced cell death in leaves of Nicotiana benthamiana. Silencing of Pt-1234 by host-induced gene silencing (HIGS) significantly reduced the virulence of Pt in the susceptible wheat variety Thatcher. The C subdomain of TaNAC069 was responsible for its interaction with Pt-1234, and the E subdomain was required for TaNAC069-mediated defense responses to Pt in planta. These findings indicate that Pt utilizes Pt-1234 to interact with wheat transcription factor TaNAC069 through its C subdomain, thereby modulating wheat immunity.