Immune gene activation by NPR and TGA transcriptional regulators in the model monocot Brachypodium distachyon. (2nd March 2022)

• Record Type: Journal Article
• Authors: Shimizu, Kohei; Suzuki, Hitomi; Uemura, Takuya; Nozawa, Akira; Desaki, Yoshitake; Hoshino, Ryosuke; Yoshida, Ayako; Abe, Hiroshi; Nishiyama, Makoto; Nishiyama, Chiharu; Sawasaki, Tatsuya; Arimura, Gen‐ichiro
• Is Part Of: Plant journal. Volume 110:Number 2(2022)
• Page Start: 470
• Page End: 481
• Publication Date: 2022-03-02
• Subjects: Brachypodium distachyon -- nonexpressor of pathogenesis‐related (NPR) -- pathogenesis‐related protein 1 (PR1) -- salicylic acid (SA) -- TGA transcription factors; Plant molecular biology -- Periodicals; Plant cells and tissues -- Periodicals; Botany -- Periodicals; 580
• DOI: 10.1111/tpj.15681
• Languages: English
• ISSNs: 0960-7412

Abstract

SUMMARY: The nonexpressor of pathogenesis‐related (NPR) gene family is well known to play a crucial role in transactivation of TGA transcription factors for salicylic acid (SA)‐responsive genes, including pathogenesis‐related protein 1 ( PR1 ), during plants' immune response after pathogen attack in the model dicot Arabidopsis thaliana . However, little is known about NPR gene functions in monocots. We therefore explored the functions of NPRs in SA signaling in the model monocot Brachypodium distachyon . BdNPR1 and BdNPR2/3 share structural similarities with A. thaliana AtNPR1/2 and AtNPR3/4 subfamilies, respectively. The transcript level of BdNPR2 but not BdNPR1 / 3 appeared to be positively regulated in leaves in response to methyl salicylate. Reporter assays in protoplasts showed that BdNPR2 positively regulated BdTGA1‐mediated activation of PR1 . This transactivation occurred in an SA‐dependent manner through SA binding at Arg468 of BdNPR2. In contrast, BdNPR1 functioned as a suppressor of BdNPR2/BdTGA1‐mediated transcription of PR1. Collectively, our findings reveal that the TGA‐promoted transcription of SA‐inducible PR1 is orchestrated by the activator BdNPR2 and the repressor BdNPR1, which function competitively in B. distachyon . Significance Statement: We present a novel function of Brachypodium distachyon NPR (BdNPR) in the transcriptional machinery for the defensin gene pathogenesis‐related 1 ( PR1 ). We address here the TGA‐activated transcriptional machinery for SA‐inducible PR1 expression, in which BdNPR2 and BdNPR1 work competitively in B. distachyon.