RESUMEN
Thioredoxins (TRXs) are important proteins involved in redox regulation of metabolism. In plants, it has been shown that the mitochondrial metabolism is regulated by the mitochondrial TRX system. However, the functional significance of TRX h2, which is found at both cytosol and mitochondria, remains unclear. Arabidopsis plants lacking TRX h2 showed delayed seed germination and reduced respiration alongside impaired stomatal and mesophyll conductance, without impacting photosynthesis under ambient O2 conditions. However, an increase in the stoichiometry of photorespiratory CO2 release was found during O2 -dependent gas exchange measurements in trxh2 mutants. Metabolite profiling of trxh2 leaves revealed alterations in key metabolites of photorespiration and in several metabolites involved in respiration and amino acid metabolism. Decreased abundance of serine hydroxymethyltransferase and glycine decarboxylase (GDC) H and L subunits as well as reduced NADH/NAD+ ratios were also observed in trxh2 mutants. We further demonstrated that the redox status of GDC-L is altered in trxh2 mutants in vivo and that recombinant TRX h2 can deactivate GDC-L in vitro, indicating that this protein is redox regulated by the TRX system. Collectively, our results demonstrate that TRX h2 plays an important role in the redox regulation of mitochondrial photorespiratory metabolism.
Asunto(s)
Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Mitocondrias/metabolismo , Tiorredoxina h/metabolismo , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Dióxido de Carbono/metabolismo , Respiración de la Célula/fisiología , Clorofila A , Regulación de la Expresión Génica de las Plantas , Glicina-Deshidrogenasa (Descarboxilante)/metabolismo , Glicina Hidroximetiltransferasa , Oxidación-Reducción , Fotosíntesis/fisiología , Hojas de la Planta/metabolismo , Tiorredoxina h/genética , TranscriptomaRESUMEN
Thioredoxin h (Trxh) is a ubiquitous protein that reduces disulfides in target proteins, and is itself reduced by NADPH-thioredoxin reductase. In the current study, the complementary DNA sequence and the genomic sequence of the three-pistil (TP) line of common wheat (Triticum aestivum L.) were obtained from spikes through reverse transcription-polymerase chain reaction (RT-PCR) and touchdown-PCR. Sequence alignment of amino acids of TPTrxh then allowed for predictions of its physicochemical properties, secondary structures, tertiary structures, and functional domains. Furthermore, the TPTrxh gene was overexpressed in Escherichia coli and its activity was demonstrated using a dithiothreitol-dependent insulin assay. The expression patterns of TPTrxh were analyzed through real-time RT-PCR in different tissues and across different developmental stages of young spikes. The complementary DNA of TPTrxh was found to be 411 bp in length, encoding 118 amino acids. Its genomic sequence was determined to be 2632 bp, possessing 3 exons and 2 introns. Functional domain analysis indicated that TPTrxh contained a WCGPC motif located at the end of the second ß-fold and on the initial side of the second α-helix. The TPTrxh protein reduces intramolecular and intermolecular disulfide bridges in target proteins. Young spikes contain higher levels of TPTrxh transcripts than do stems and leaves. The transcript levels in the young spikes (2-5 mm in length) of the Chinese Spring TP line increased 2.84-fold relative to those of young spikes (2-5 mm in length) of the Chinese Spring line. These data provide a basis for future research into the function of Trxh, and offer further insight into the molecular mechanism of the TP mutation in wheat.
Asunto(s)
Proteínas de Plantas/química , Tiorredoxina h/química , Triticum/química , Secuencias de Aminoácidos , Secuencia de Aminoácidos , Secuencia de Bases , Clonación Molecular , Exones , Datos de Secuencia Molecular , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Estructura Terciaria de Proteína , Tiorredoxina h/genética , Tiorredoxina h/metabolismo , Transcripción Genética , Triticum/enzimologíaRESUMEN
The cDNA code of thioredoxin h, designated as HbTRX1, was isolated from Hevea brasiliensis by rapid amplification of cDNA ends. HbTRX1 contained a 542-bp open reading frame encoding 123 amino acids. The deduced HbTRX1 protein showing high identity to thioredoxin h of other plant species was predicted to possess the conserved catalytic site WCXPC. Semiquantitative reverse transcription-polymerase chain reaction analysis revealed that HbTRX1 was constitutively expressed in all tested tissues. HbTRX1 transcripts accumulated at relatively low levels in the flower, somatic embryo, and leaves, while HbTRX1 transcripts accumulated at relatively high levels in the callus and latex. The HbTRX1 transcript was expressed at different levels, with higher levels in self-rooting juvenile clones than in their donor clones. HbTRX1 was expressed in Escherichia coli, and its activity was demonstrated using the dithiothreitol-dependent insulin assay. This work provides a basis for studying the biological function of thioredoxin h in rubber tree.