Mechanistic basis by which the Prf resistance protein manipulates the defense-related NAC1 transcription factor
J. KUD (1), X. Niu (2), W. Wang (1), Y. Liu (2), F. Xiao (1) (1) University of Idaho, U.S.A.; (2) Hefei University of Technology, China

The successful resistance to pathogen infection relies on effective recognition of the intruder, followed by rapid transcriptional reprogramming to activate defense responses. In tomato, resistance to bacterial speck disease caused by Pseudomonas syringae pv. tomato (Pst) is determined by Prf, a NB-LRR type resistance (R) protein. Although the recognition of Pst by Prf is well studied, the knowledge about the downstream signaling events leading to the expression of defense-related genes is limited. We earlier showed that a defense-related tomato NAC1 transcription factor is induced during Pst infection and silencing of the NAC1 gene attenuates resistance to Pst, suggesting an important role for NAC1 in the Prf-mediated disease resistance. We now have found the NAC1 protein is ubiquitinted by an ubiquitin E3 ligase NAI (NAC1 interacting protein). Also, the Pst-regulated expression of NAC1 and NAI1 genes are inversely correlated. Nevertheless, the auto-active PrfD1416V mutant, but not the wild-type Prf, can interact with and stabilize NAC1. A limited number of R proteins have been found to bind to transcription factors. Thus, we seek to identify the mechanism by which Prf controls transcriptional reprogramming via manipulation of NAC1 during defense responses. Our biochemical results support the hypothesis that, upon activation by Pst, the activated Prf binds to NAC1 to sequester it away from NAI1, thereby preventing the NAI1-mediated ubiquitination/degradation of NAC1.

Abstract Number: P17-550
Session Type: Poster