Ectopically expressed glutaredoxin ROXY19 negatively regulates the detoxification pathway in Arabidopsis thaliana.
Glutaredoxins (GRXs) are small proteins which bind glutathione to either reduce disulfide bonds or to coordinate iron sulfur clusters. Whereas these well-established functions are associated with ubiquitously occurring GRXs that encode variants of a CPYC or a CGFS motif in the active center, land plants also possess CCxC/S-type GRXs (named ROXYs) for which the biochemical functions are yet unknown. ROXYs physically and genetically interact with bZIP transcription factors of the TGA family. In Arabidopsis, ectopically expressed ROXY19 (originally named GRX480 or GRXC9) negatively regulates expression of jasmonic acid/ethylene-induced defense genes through an unknown mechanism that requires at least one of the redundant transcription factors TGA2, TGA5 or TGA6.



Ectopically expressed ROXY19 interferes with the activation of TGA-dependent detoxification genes. Similar to the tga2 tga5 tga6 mutant, 35S:ROXY19 plants are more susceptible to the harmful chemical TIBA (2,3,5-triiodobenzoic acid). The repressive function of ROXY19 depends on the integrity of the active site, which can be either CCMC or CPYC but not SSMS. Ectopic expression of the related GRX ROXY18/GRXS13 also led to increased susceptibility to TIBA, indicating potential functional redundancy of members of the ROXY gene family. This redundancy might explain why roxy19 knock-out plants did not show a phenotype with respect to the regulation of the TIBA-induced detoxification program. Complementation of the tga2 tga5 tga6 mutant with either TGA5 or TGA5C186S, in which the single potential target-site of ROXY19 had been eliminated, did not reveal any evidence for a critical redox modification that might be important for controlling the detoxification program.



ROXY19 and related proteins of the ROXY gene family can function as negative regulators of TGA-dependent promoters controlling detoxification genes.
Albrecht-von-Haller-Institute for Plant Sciences, Molecular Biology and Physiology, Georg-August-University Göttingen, Julia-Lermontowa-Weg 3, 37077, Göttingen, Germany.
Li-Jun
LJ
Huang
Albrecht-von-Haller-Institute for Plant Sciences, Molecular Biology and Physiology, Georg-August-University Göttingen, Julia-Lermontowa-Weg 3, 37077, Göttingen, Germany.
Ning
N
Li
Albrecht-von-Haller-Institute for Plant Sciences, Molecular Biology and Physiology, Georg-August-University Göttingen, Julia-Lermontowa-Weg 3, 37077, Göttingen, Germany.
Corinna
C
Thurow
Centre for Organismal Studies, Heidelberg University, 69120, Heidelberg, Germany.
Markus
M
Wirtz
Centre for Organismal Studies, Heidelberg University, 69120, Heidelberg, Germany.
Rüdiger
R
Hell
Albrecht-von-Haller-Institute for Plant Sciences, Molecular Biology and Physiology, Georg-August-University Göttingen, Julia-Lermontowa-Weg 3, 37077, Göttingen, Germany. cgatz@gwdg.de.
Christiane
0000-0003-2741-8514
C
Gatz
D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D003517:Cyclopentanes / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D054477:Glutaredoxins / Q000235:genetics* / Q000378:metabolism; D054883:Oxylipins / Q000378:metabolism; D011401:Promoter Regions, Genetic; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014283:Triiodobenzoic Acids / Q000633:toxicity*
D029681:Arabidopsis Proteins; D003517:Cyclopentanes; D054477:Glutaredoxins; D054883:Oxylipins; C000621882:ROXY19 protein, Arabidopsis; D014157:Transcription Factors; D014283:Triiodobenzoic Acids; C011006:jasmonic acid; C052968:2,3,5-triiodobenzoic acid
Detoxification program; ROXY-type glutaredoxins; Repression; TGA transcription factors