Electron Transfer Pathways and Dynamics of Chloroplast NADPH-dependent Thioredoxin Reductase C (NTRC)

Bernal‐Bayard, Pilar; Hervás, Manuel; Cejudo, Francisco Javier; Navarro, José A.

doi:10.1074/jbc.m112.388991

Cited by 32 publications

(34 citation statements)

References 40 publications

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“…Thioredoxin reductases are homodimeric enzymes that catalyze the NADPH-dependent reduction of cellular thioredoxins (Hirt et al, 2002; Bernal-Bayard et al, 2012). We report here that the full-length NTRC polypeptides extracted from Arabidopsis leaves in the presence or absence of DTT ( Figure 9 ) exist as homodimers that are resistant to detergent treatment without heating, suggesting that the dimeric structure of chloroplast NTRC is stable without any disulphide bridges between the monomers ( Figure 8B ).…”

Section: Discussionmentioning

confidence: 99%

“…The 3-D model of the NTRC dimer ( Figure 8A ) showed that the TRXd is connected to the NTRd by a long linker region that allows some flexibility for the position of the TRXd. Recently, Bernal-Bayard et al (2012) suggested that a conformational change takes place in the NTRC dimer after reduction of TRXd active site that allows the reaction between TRXd and its target protein. This structural change also exposes the NTR active site (Bernal-Bayard et al, 2012, see also the location of 2-Cys motifs of NTRC in Figure 8A ), which may promote the interaction between NTRd of NTRC and free thioredoxins.…”

Section: Discussionmentioning

confidence: 99%

“…Recently, Bernal-Bayard et al (2012) suggested that a conformational change takes place in the NTRC dimer after reduction of TRXd active site that allows the reaction between TRXd and its target protein. This structural change also exposes the NTR active site (Bernal-Bayard et al, 2012, see also the location of 2-Cys motifs of NTRC in Figure 8A ), which may promote the interaction between NTRd of NTRC and free thioredoxins. The Y2H test failed to show any interactions of NTRC or NTRd with TRXd ( Figure 10 ).…”

Section: Discussionmentioning

confidence: 99%

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Overexpression of chloroplast NADPH-dependent thioredoxin reductase in Arabidopsis enhances leaf growth and elucidates in vivo function of reductase and thioredoxin domains

et al. 2013

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Plant chloroplasts have versatile thioredoxin systems including two thioredoxin reductases and multiple types of thioredoxins. Plastid-localized NADPH-dependent thioredoxin reductase (NTRC) contains both reductase (NTRd) and thioredoxin (TRXd) domains in a single polypeptide and forms homodimers. To study the action of NTRC and NTRC domains in vivo, we have complemented the ntrc knockout line of Arabidopsis with the wild type and full-length NTRC genes, in which 2-Cys motifs either in NTRd, or in TRXd were inactivated. The ntrc line was also transformed either with the truncated NTRd or TRXd alone. Overexpression of wild-type NTRC promoted plant growth by increasing leaf size and biomass yield of the rosettes. Complementation of the ntrc line with the full-length NTRC gene containing an active reductase but an inactive TRXd, or vice versa, recovered wild-type chloroplast phenotype and, partly, rosette biomass production, indicating that the NTRC domains are capable of interacting with other chloroplast thioredoxin systems. Overexpression of truncated NTRd or TRXd in ntrc background did not restore wild-type phenotype. Modeling of the three-dimensional structure of the NTRC dimer indicates extensive interactions between the NTR domains and the TRX domains further stabilize the dimeric structure. The long linker region between the NTRd and TRXd, however, allows flexibility for the position of the TRXd in the dimer. Supplementation of the TRXd in the NTRC homodimer model by free chloroplast thioredoxins indicated that TRXf is the most likely partner to interact with NTRC. We propose that overexpression of NTRC promotes plant biomass yield both directly by stimulation of chloroplast biosynthetic and protective pathways controlled by NTRC and indirectly via free chloroplast thioredoxins. Our data indicate that overexpression of chloroplast thiol redox-regulator has a potential to increase biofuel yield in plant and algal species suitable for sustainable bioenergy production.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Overexpression of chloroplast NADPH-dependent thioredoxin reductase in Arabidopsis enhances leaf growth and elucidates in vivo function of reductase and thioredoxin domains

et al. 2013

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“…NTRC-deficient plants display obvious phenotypes with palegreen leaves (12,13), indicating that NTRC-dependent redox regulation in chloroplasts has an important role in plants. Although target proteins (13)(14)(15)(16) and catalytic mechanisms (17,18) for NTRC have been partly reported to date, its physiological importance, especially in the context of functional differences from the FTR/Trx system, is largely uncharacterized.…”

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confidence: 99%

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

Yoshida

Hisabori

2016

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

123

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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“…Though not experimentally established, it is expected that Trx x and CDSP32 use the reducing power of reduced ferredoxin (Fd) in a reaction catalyzed by Fd-dependent Trx reductase (FTR). Results from our group show that NTRC is unable to reduce plastidial Trxs, such as Trx x or CDSP32 (Pérez-Ruiz et al, 2006; Bernal-Bayard et al, 2012). Therefore, it seems that the two different pathways, NTRC and FTR/Trx, for 2-Cys Prx reduction are not connected.…”

Section: The Pathways Of 2-cys Prxs Reduction In Chloroplastsmentioning

confidence: 87%

Overoxidation of chloroplast 2-Cys peroxiredoxins: balancing toxic and signaling activities of hydrogen peroxide

Puerto-Galán¹,

Pérez-Ruiz²,

Ferrández³

et al. 2013

Front. Plant Sci.

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Photosynthesis, the primary source of biomass and oxygen into the biosphere, involves the transport of electrons in the presence of oxygen and, therefore, chloroplasts constitute an important source of reactive oxygen species, including hydrogen peroxide. If accumulated at high level, hydrogen peroxide may exert a toxic effect; however, it is as well an important second messenger. In order to balance the toxic and signaling activities of hydrogen peroxide its level has to be tightly controlled. To this end, chloroplasts are equipped with different antioxidant systems such as 2-Cys peroxiredoxins (2-Cys Prxs), thiol-based peroxidases able to reduce hydrogen and organic peroxides. At high peroxide concentrations the peroxidase function of 2-Cys Prxs may become inactivated through a process of overoxidation. This inactivation has been proposed to explain the signaling function of hydrogen peroxide in eukaryotes, whereas in prokaryotes, the 2-Cys Prxs of which were considered to be insensitive to overoxidation, the signaling activity of hydrogen peroxide is less relevant. Here we discuss the current knowledge about the mechanisms controlling 2-Cys Prx overoxidation in chloroplasts, organelles with an important signaling function in plants. Given the prokaryotic origin of chloroplasts, we discuss the occurrence of 2-Cys Prx overoxidation in cyanobacteria with the aim of identifying similarities between chloroplasts and their ancestors regarding their response to hydrogen peroxide.

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Electron Transfer Pathways and Dynamics of Chloroplast NADPH-dependent Thioredoxin Reductase C (NTRC)

Cited by 32 publications

References 40 publications

Overexpression of chloroplast NADPH-dependent thioredoxin reductase in Arabidopsis enhances leaf growth and elucidates in vivo function of reductase and thioredoxin domains

Overexpression of chloroplast NADPH-dependent thioredoxin reductase in Arabidopsis enhances leaf growth and elucidates in vivo function of reductase and thioredoxin domains

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

Overoxidation of chloroplast 2-Cys peroxiredoxins: balancing toxic and signaling activities of hydrogen peroxide

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