Inactivation of Thioredoxin Reductases Reveals a Complex Interplay between Thioredoxin and Glutathione Pathways in <i>Arabidopsis</i> Development

Reichheld, Jean‐Philippe; Khafif, Mehdi; Riondet, Christophe; Droux, Michel; Bonnard, Géraldine; Meyer, Yves

doi:10.1105/tpc.107.050849

Cited by 231 publications

(275 citation statements)

References 63 publications

(65 reference statements)

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“…The CC-type class expanded exclusively and strongly during the evolution of land plants, suggesting that this class of GRXs might have been recruited to participate in the evolution of more complex land plants (Xing et al, 2006;Ziemann et al, 2009). Contrasting with wide-ranging roles of plant thioredoxins in chloroplast and mitochondrial processes, seed development and germination, and auxin signaling (Buchanan and Balmer, 2005;Reichheld et al, 2007;Arsova et al, 2010;Bashandy et al, 2010), the biological and physiological functions of plant GRXs have remained largely elusive. Recently, two CC-type GRX genes, ROXY1 and ROXY2, were functionally characterized, revealing their functions during Arabidopsis flower development Xing and Zachgo, 2008;).…”

mentioning

confidence: 99%

The ROXY1 C-Terminal L**LL Motif Is Essential for the Interaction with TGA Transcription Factors

Gutsche

Zachgo

2011

Plant Physiology

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Glutaredoxins (GRXs) are small, ubiquitous, glutathione-dependent oxidoreductases that participate in redox-regulated processes associated with stress responses. Recently, GRXs have been shown to exert crucial functions during flower developmental processes. GRXs modulate their target protein activities by the reduction of protein disulfide bonds or deglutathionylation reactions. The Arabidopsis (Arabidopsis thaliana) GRX ROXY1 participates in petal primordia initiation and further petal morphogenesis. ROXY1 belongs to a land plant-specific class of GRXs with a CC-type active site motif, deviating from the ubiquitously occurring CPYC and CGFS GRX classes. ROXY1 was previously shown to interact with floral TGA transcription factors in the nucleus, and this interaction is a prerequisite for ROXY1 to exert its activity required for Arabidopsis petal development. Deletion analysis further identified the importance of the ROXY1 C terminus for the ROXY1/ TGA protein interactions and for the ROXY1 function in petal development. Here, by dissecting the ROXY1 C terminus, an a-helical L**LL motif immediately adjacent to the ROXY1 C-terminal eight amino acids was identified that is essential for the interaction with TGA transcription factors and crucial for the ROXY1 function in planta. Similar to the a-helical L**LL motifs binding to transcriptional coactivators with liganded nuclear receptors in animals, a hydrophobic face formed by the conserved leucines in the L**LL motif of ROXY1 possibly mediates the interaction with TGA transcription factors. Thus, the a-helical L**LL sequence is a conserved protein-protein interaction motif in both animals and plants. Furthermore, two separate TGA domains were identified by deletion experiments as being essential for mediating TGA protein interactions with ROXYs.

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confidence: 99%

The ROXY1 C-Terminal L**LL Motif Is Essential for the Interaction with TGA Transcription Factors

Gutsche

Zachgo

2011

Plant Physiology

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“…Recently indirect evidence for such a protein in Arabidopsis was reported [26]. The results of the TrxR activity assay argue against the existence of another major source of Trx1 reducing activity in HeLa cells, but it is possible that other enzymes that could reduce Trx1 may not be fully active under the assay conditions used here.…”

Section: Discussionmentioning

confidence: 77%

Thioredoxin reductase-1 knock down does not result in thioredoxin-1 oxidation

Watson

Heilman

Hughes

et al. 2008

Biochemical and Biophysical Research Communications

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The active site of thioredoxin-1 (Trx1) is oxidized in cells with increased reactive oxygen species (ROS) and is reduced by thioredoxin reductase-1 (TrxR1). The purpose of the present study was to determine the extent to which the redox state of Trx1 is sensitive to changes in these opposing reactions. Trx1 redox state and ROS generation were measured in cells exposed to the TrxR1 inhibitors aurothioglucose (ATG) and monomethylarsonous acid (MMA(III)) and in cells depleted of TrxR1 activity by siRNA knock down. The results showed that all 3 treatments inhibited TrxR1 activity to similar extents (90% inhibition), but that only MMA(III) exposure resulted in oxidation of Trx1. Similarly, ROS levels were elevated in response to MMA(III), but not in response to ATG or TrxR1 siRNA. Therefore, TrxR1 inhibition alone was not sufficient to oxidize Trx1, suggesting that Trx1-independent pathways should be considered when evaluating pharmacological and toxicological mechanisms involving TrxR1 inhibition.

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“…3C). Furthermore, the glutathione system is likely to participate in the chloroplast redox network in vivo, as reported in the cytosol (57)(58)(59). For example, the stable redox state of PrxQ even in ftrb ntrc (Fig.…”

Section: Discussionmentioning

confidence: 99%

Two distinct redox cascades cooperatively regulate chloroplast functions and sustain plant viability

Yoshida

Hisabori

2016

Proc. Natl. Acad. Sci. U.S.A.

120

182

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The thiol-based redox regulation system is believed to adjust chloroplast functions in response to changes in light environments. A redox cascade via the ferredoxin-thioredoxin reductase (FTR)/thioredoxin (Trx) pathway has been traditionally considered to serve as a transmitter of light signals to target enzymes. However, emerging data indicate that chloroplasts have a complex redox network composed of diverse redox-mediator proteins and target enzymes. Despite extensive research addressing this system, two fundamental questions are still unresolved: How are redox pathways orchestrated within chloroplasts, and why are chloroplasts endowed with a complicated redox network? In this report, we show that NADPH-Trx reductase C (NTRC) is a key redox-mediator protein responsible for regulatory functions distinct from those of the classically known FTR/Trx system. Target screening and subsequent biochemical assays indicated that NTRC and the Trx family differentially recognize their target proteins. In addition, we found that NTRC is an electron donor to Trx-z, which is a key regulator of gene expression in chloroplasts. We further demonstrate that cooperative control of chloroplast functions via the FTR/Trx and NTRC pathways is essential for plant viability. Arabidopsis double mutants impaired in FTR and NTRC expression displayed lethal phenotypes under autotrophic growth conditions. This severe growth phenotype was related to a drastic loss of photosynthetic performance. These combined results provide an expanded map of the chloroplast redox network and its biological functions.T o preserve the integrity and efficiency of photosynthesis and other metabolic reactions, chloroplast enzymes need to be flexibly and appropriately controlled in response to changes in light environments. The photosynthetic electron transport chain in the chloroplast thylakoid membrane converts light energy into chemical energy, which is captured and stored in ATP and NADPH. These molecules are primarily consumed by the Calvin-Benson cycle in the stroma, but part of the reducing power is used for other metabolic reactions in chloroplasts (e.g., nitrogen and sulfur metabolism). One pathway for the reducing power is the redox cascade, mediated by ferredoxin-thioredoxin reductase (FTR) and thioredoxin (Trx). In this system, FTR receives reducing power from the light-driven photosynthetic electron transport chain via ferredoxin and then donates the reducing power to Trx. A reduced form of Trx subsequently transfers reducing power to target proteins through a dithiol-disulfide exchange reaction, allowing the targets to modulate the enzymatic activities. The redox cascade via the FTR/Trx pathway provides the basis for thiol-based redox regulation in chloroplasts and ensures light-responsive control of chloroplast functions (1, 2).The FTR/Trx pathway has been considered the only pathway regulating redox reactions in chloroplasts. Information about its target proteins has also been limited to a specific set of lightactivated enzymes, such as some enzy...

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Inactivation of Thioredoxin Reductases Reveals a Complex Interplay between Thioredoxin and Glutathione Pathways in Arabidopsis Development

Cited by 231 publications

References 63 publications

The ROXY1 C-Terminal L**LL Motif Is Essential for the Interaction with TGA Transcription Factors

The ROXY1 C-Terminal L**LL Motif Is Essential for the Interaction with TGA Transcription Factors

Thioredoxin reductase-1 knock down does not result in thioredoxin-1 oxidation

Two distinct redox cascades cooperatively regulate chloroplast functions and sustain plant viability

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