Glutaredoxins and thioredoxins in plants

Abstract

During the 70s and 80s two plant thioredoxin systems were identified. The chloroplastic system is composed of a ferredoxin-dependent thioredoxin, with two thioredoxin types (m and f) regulating the activity of enzymes implicated in photosynthetic carbon assimilation. In the cytosol of heterotrophic tissues, an NADP dependent thioredoxin reductase and a thioredoxin (h) were identified. The first plant glutaredoxin was only identified later, in 1994. Our view of plant thioredoxins and glutaredoxins was profoundly modified by the sequencing programs which revealed an unexpected number of genes encoding not only the previously identified disulfide reductases, but also numerous new types. At the same time it became clear that plant genomes encode chloroplastic, cytosolic and mitochondrial peroxiredoxins, suggesting a major role for redoxins in anti-oxidant defense. Efficient proteomics approaches were developed allowing the characterization of numerous thioredoxin target proteins. They are implicated in different aspects of plant life including development and adaptation to environmental changes and stresses. The most important challenge for the next years will probably be to identify in planta which redoxin reduces which target, a question which remains unsolved due to the low specificities of redoxins in vitro and the numerous redundancies which in most cases mask the phenotype of redoxin mutants.

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

“…However, plant genome sequences indicated that as many as five Trx subtypes (f, m, x, y, and z) are targeted to chloroplasts (3,4). Other putative redox-mediator proteins, including several Trx-like proteins and glutaredoxins, were also reported to be localized in chloroplasts (5,6). Furthermore, recently developed proteomic techniques and methodologies for screening Trx target proteins have identified potential redox-regulated proteins associated with a broad spectrum of chloroplast functions (7)(8)(9)(10)(11).…”

Plant Thioredoxin CDSP32 Regenerates 1-Cys Methionine Sulfoxide Reductase B Activity through the Direct Reduction of Sulfenic Acid

“…ubiquitous protein-disulfide reductases that supply the reducing power needed to break disulfide bonds in physiological partners (1,2). Grxs, generally reduced by glutathione, are able to reduce protein disulfides and also to carry out the reduction of glutathione-mixed disulfides, a reaction termed deglutathionylation, for which Trxs are not efficient catalysts (3)(4)(5).…”

A cold‐induced thioredoxin h of rice, OsTrx23, negatively regulates kinase activities of OsMPK3 and OsMPK6 in vitro

“…In rice, thirty potential thioredoxin-encoding genes (OsTrxs) have been identified; nine genes of which were predicted to encode Trx h [10]. Meanwhile, eleven thioredoxin h genes have been recently identified in Arabidopsis [2].…”

“…Two cysteine residues in the active site provide sulfhydryl groups that are involved in a reducing activity. The reduced form of thioredoxin, Trx-(SH) 2 , reduces disulfide bonds of target proteins, while the oxidized form, Trx-S 2 , contains a disulfide bond within the active site, which is reduced to Trx-(SH) 2 dithiol by NADPH and Trx reductases [2].…”

“…NTRs belong to a superfamily of flavoprotein disulfide oxidoreductases [5] and transfer electrons from NADPH to the active site disulfide bonds of oxidized Trx h via FAD [6]. Plant Trx h proteins are implicated in many cellular processes, including protein folding, protein repair after damage by oxidation, sulfur metabolism, and regulation of transcription factors [2]. Trx h proteins are also involved in plant development and stress responses, such as seed germination and early seedling development [7], self-incompatibility reactions [8] and oxidative stress [9].…”