Peroxiredoxins and NADPH-Dependent Thioredoxin Systems in the Model Legume Lotus japonicus      

Abstract

Peroxiredoxins (Prxs), thioredoxins (Trxs), and NADPH-thioredoxin reductases (NTRs) constitute central elements of the thioldisulfide redox regulatory network of plant cells. This study provides a comprehensive survey of this network in the model legume Lotus japonicus. The aims were to identify and characterize these gene families and to assess whether the NTR-Trx systems are operative in nodules. Quantitative reverse transcription-polymerase chain reaction and immunological and proteomic approaches were used for expression profiling. We identified seven Prx, 14 Trx, and three NTR functional genes. The PrxQ1 gene was found to be transcribed in two alternative spliced variants and to be expressed at high levels in leaves, stems, petals, pods, and seeds and at low levels in roots and nodules. The 1CPrx gene showed very high expression in the seed embryos and low expression in vegetative tissues and was induced by nitric oxide and cytokinins. In sharp contrast, cytokinins down-regulated all other Prx genes, except PrxQ1, in roots and nodules, but only 2CPrxA and PrxQ1 in leaves. Gene-specific changes in Prx expression were also observed in response to ethylene, abscisic acid, and auxins. Nodules contain significant mRNA and protein amounts of cytosolic PrxIIB, Trxh1, and NTRA and of plastidic NTRC. Likewise, they express cytosolic Trxh3, Trxh4, Trxh8, and Trxh9, mitochondrial PrxIIF and Trxo, and plastidic Trxm2, Trxm4, and ferredoxin-Trx reductase. These findings reveal a complex regulation of Prxs that is dependent on the isoform, tissue, and signaling molecule and support that redox NTR-Trx systems are functional in the cytosol, mitochondria, and plastids of nodules.

Evidence for a Role of Chloroplastic m-Type Thioredoxins in the Biogenesis of Photosystem II in Arabidopsis

“…Among the target proteins of TRX m, 2-Cys peroxiredoxin is an important antioxidant for hydrogen peroxide (H 2 O 2 ) detoxification in chloroplast (König et al, 2002;Dietz and Pfannschmidt, 2011;Tovar-Méndez et al, 2011). Previous studies suggest that TRX m proteins are able to reduce the oxidative state of 2-Cys peroxiredoxin to maintain the metabolic balance of reactive oxygen species (ROS; Collin et al, 2003;Chi et al, 2008).…”

Thioredoxin Redox Regulates ATPase Activity of Magnesium Chelatase CHLI Subunit and Modulates Redox-Mediated Signaling in Tetrapyrrole Biosynthesis and Homeostasis of Reactive Oxygen Species in Pea Plants

“…In general, the main redox-regulatory network in chloroplasts consists of NADPH-dependent TRX reductase C (NTRC), all plastidal TRXs, plastidal peroxiredoxins, and the glutathione/glutaredoxin system (Kirchsteiger et al, 2009;Pulido et al, 2010;Dietz and Pfannschmidt, 2011;Tovar-Méndez et al, 2011). Recently, the comprehensive analysis of an Arabidopsis knockout mutant for NTRC revealed that NTRC may redox regulate several enzymes and thus modulate the expression of genes involved in chlorophyll synthesis (Stenbaek et al, 2008;Lepistö et al, 2009).…”

“…Among the target proteins for these TRX isoforms is 2-Cys Prx, which is involved in peroxide detoxification in the chloroplast during the dark phase (König et al, 2002;Pulido et al, 2010;Dietz, 2011;Tovar-Méndez et al, 2011). TRX-F and TRX-M are able to reduce oxidized 2-Cys Prx (Chi et al, 2008).…”

Redox signals as a language of interorganellar communication in plant cells

“…The thiol/disulfide turnover participates in turning on/off the function of proteins and in modifying the activity of transcription factors and enzymes [21]. As the Trxs system is linked to photosynthetic light reactions, its role will be addressed in the next section.…”