Repression of the Arabidopsis thaliana Jasmonic Acid/Ethylene-Induced Defense Pathway by TGA-Interacting Glutaredoxins Depends on Their C-Terminal ALWL Motif

Abstract

Glutaredoxins are small heat-stable oxidoreductases that transfer electrons from glutathione (GSH) to oxidized cysteine residues, thereby contributing to protein integrity and regulation. In Arabidopsis thaliana, floral glutaredoxins ROXY1 and ROXY2 and pathogen-induced ROXY19/GRX480 interact with bZIP transcription factors of the TGACG (TGA) motif-binding family. ROXY1, ROXY2, and TGA factors PERIANTHIA, TGA9, and TGA10 play essential roles in floral development. In contrast, ectopically expressed ROXY19/GRX480 negatively regulates expression of jasmonic acid (JA)/ethylene (ET)-induced defense genes through an unknown mechanism that requires clade II transcription factors TGA2, TGA5, and/or TGA6. Here, we report that at least 17 of the 21 land plant-specific glutaredoxins encoded in the Arabidopsis genome interact with TGA2 in a yeast-two-hybrid system. To investigate their capacity to interfere with the expression of JA/ET-induced genes, we developed a transient expression system. Activation of the ORA59 (OCTADECANOID-RESPONSIVE ARABIDOPSIS AP2/ERF-domain protein 59) promoter by transcription factor EIN3 (ETHYLENE INSENSITVE 3) was suppressed by co-expressed ROXY19/GRX480. Suppression depended on the L**LL motif in the C-terminus of ROXY19/GRX480. This putative protein interaction domain was recently described as being essential for the TGA/ROXY interaction. Ten of the 17 tested ROXY proteins suppressed ORA59 promoter activity, which correlated with the presence of the C-terminal ALWL motif, which is essential for ROXY1 function in flower development. ROXY19/GRX480-mediated repression depended on the GSH binding site, suggesting that redox modification of either TGA factors or as yet unknown target proteins is important for the suppression of ORA59 promoter activity.

A Maize Glutaredoxin Gene,Abphyl2,Regulates Shoot Meristem Size and Phyllotaxy

“…Our map-based cloning revealed that Abph2 encodes a GRX gene. Plant GRXs function in defense against various stresses, hormone signaling, and flower development (Ndamukong et al, 2007;Cheng, 2008;Xing and Zachgo, 2008;Guo et al, 2010;Cheng et al, 2011;Zander et al, 2012). Remarkably, we found that Abph2 arose by a transposition of MSCA1, and this rearrangement was presumably caused by the ionizing radiation that induced the Abph2 mutation.…”

“…Based on the conserved active site sequences, plant GRXs are divided into CPYC-, CGFC-, and CC-type classes. Plant GRX genes function in stress and pathogen responses (Ndamukong et al, 2007;Cheng, 2008;Guo et al, 2010) as well as jasmonic acid, gibberellic acid, and auxin signaling (Hou et al, 2008;Cheng et al, 2011;Zander et al, 2012). In Arabidopsis, two related CC-type GRX genes, ROXY1 and 2, were found to function in flower development (Xing et al, 2005(Xing et al, , 2006Xing and Zachgo, 2008).…”

Salicylic Acid Suppresses Jasmonic Acid Signaling Downstream of SCFCOI1-JAZ by Targeting GCC Promoter Motifs via Transcription Factor ORA59

“…We found that the GCC-box is sufficient for transcriptional activation by JA and suppression by SA and suggest that SA/JA crosstalk via the GCC-box is mediated through SA-mediated suppression of ORA59 protein accumulation. Like PDF1.2, the promoter of ORA59 contains a GCC-box and can be suppressed by SA (Zander et al, 2012). However, we showed that this is not required for SA-mediated suppression of JA-dependent PDF1.2 gene expression, as in the ERF1 overexpression line the level of ORA59 transcript is not affected by SA while the at same time the PDF1.2 expression level is reduced by SA ( Figure 6A).…”

A tandem affinity purification tag of TGA2 for isolation of interacting proteins in Arabidopsis thaliana

“…5 Unique Peptides displays the number of peptide sequences unique to a protein group. 6 Peptides displays the number of distinct peptide sequences in the protein group. 7 PSM displays the total number of identified peptide sequences (PSMs) for the protein, including those redundantly identified.…”

“…3,4 TGA factors belong to the basic region/leucine zipper motif (bZIP) superfamily of transcription factors; 5 they bind to tfhe TGACG motif to regulate defense and developmental processes. 6,7 Different methods have been used to study interactions between TGA factors and other proteins. Y2H screens were used to show that 7 TGA factors differentially interact with a key regulator of systemic acquired resistance (SAR), NPR1.…”