TCP Transcription Factors Interact With NPR1 and Contribute Redundantly to Systemic Acquired Resistance.

In , TEOSINTE BRANCHED 1, CYCLOIDEA, PCF1 (TCP) transcription factors (TF) play critical functions in developmental processes. Recent studies suggest they also function in plant immunity, but whether they play an important role in systemic acquired resistance (SAR) is still unknown. NON-EXPRESSER OF PR GENES 1 (NPR1), as an essential transcriptional regulatory node in SAR, exerts its regulatory role in downstream genes expression through interaction with TFs. In this work, we provide biochemical and genetic evidence that TCP8, TCP14, and TCP15 are involved in the SAR signaling pathway. TCP8, TCP14, and TCP15 physically interacted with NPR1 in yeast two-hybrid assays, and these interactions were further confirmed . SAR against the infection of virulent strain pv. () ES4326 in the triple T-DNA insertion mutant was partially compromised compared with Columbia 0 (Col-0) wild type plants. The induction of SAR marker genes , and in local and systemic leaves was dramatically decreased in the mutant compared with that in Col-0 after local treatment with ES4326 carrying . Results from yeast one-hybrid and chromatin immunoprecipitation (ChIP) assays demonstrated that TCP15 can bind to a conserved TCP binding motif, GCGGGAC, within the promoter of , and this binding was enhanced by NPR1. Results from RT-qPCR assays showed that TCP15 promotes the expression of in response to salicylic acid induction. Taken together, these data reveal that TCP8, TCP14, and TCP15 physically interact with NPR1 and function redundantly to establish SAR, that TCP15 promotes the expression of through directly binding a TCP binding site within the promoter of , and that this binding is enhanced by NPR1.