Os07g0186000
As a subgroup I h-type Trx in rice, OsTRXh1 regulates the redox state of the apoplast and influences plant development and stress responses[1][2].
Contents
Annotated Information
Function
OsTRXh1 could be secreted into the rice apoplast by transient expression and immunohistochemistry experiments. Furthermore, in the apoplast of rice, OsTRXh1 was induced by salt stress at the protein level. It has a conserved redox-active site (WCGPC), which involves in the redox status regulation of target proteins. OsTRXh1 not only had the ability to reduce insulin in the presence of DTT but also it can complement the hydrogen peroxide sensitivity of the thioredoxin-deficient yeast mutant. OsTRXh1 possesses disulfide reductase activity and could be secreted into the extracellular regions. The knockdown and overexpression transgenic plants in rice showed that it involved in salt and ABA response regulation. More hydrogen peroxide was produced in the extracellular space of OsTRXh1 knockdown plants than in wild-type plants under salt stress, whereas the OsTRXh1 overexpression plants produced less hydrogen peroxide under the same conditions,which suggesting that OsTRXh1 regulated apoplastic ROS accumulation and influenced plant stress responses in rice[1][2]. Recently, a report showed that OsTRXh1 was induced by cold stress and negatively regulated the kinase activities of Oryza sativa Mitogen-activated Protein Kinase3 (OsMPK3) and OsMPK6 in vitro through a redox-dependent mechanism[3].
GO assignment(s): GO:0005489, GO:0006118
Mutation
To test whether OsTRXh1 has the ability to complement the yeast mutant, the full-length cDNA of OsTRXh1 and the OsTRXh1C43S mutant were introduced into the yeast mutant[2].The yeast mutant cells expressing the wild type OsTRXh1 grew as well as the positive control, whereas the transformants expressing the OsTRXh1C43S mutant did not grow in the culture medium containing H2O2 (Figure 1). All transformed yeast mutant cells grew well in medium that did not contain H2O2. These results indicate that OsTRXh1 had the ability to complement the H2O2 hypersensitivity of the trx1△ trx2△ yeast mutant but the OsTRXh1C43S mutant did not[2].
Expression
- OsTRXh1 is a salt and abscisic acid response gene and is extensively expressed:
The OsTRXh1 mRNA expression levels were slightly increased after treatment with 100 mM NaCl for 3 h, and a nearly 2.2-fold increase was observed after treatment for 6 h (Fig. 2A). We also found that OsTRXh1 expression was slightly induced by abscisic acid (ABA; Fig. 2B). The expression level of its homologous gene, OsTRXh2, was lower as compared with OsTRXh1 in whole plants under the same conditions(Fig. 2, A and B). The expression analysis of OsTRXh1 under normal conditions using RT-PCR showed that OsTRXh1 was expressed in all of the tissues examined, and the level of transcription was abundant in leaves and nodes(Fig. 5C).During seed germination, GUS staining was detected at the radicle, germ (Fig. 2, D and E), bud, and root of 5-d-old seedlings (Fig. 2F). In seedlings, OsTRXh1 was expressed in the leaf, root, and shoot apical meristem (Fig. 2, G–I). In mature rice plants, staining was detected in the stem and node (Fig.2, J and K). We could also detect OsTRXh1 expression in the palea, lodicule, stamen, pistil, and panicle during the reproductive phase (Fig. 2, L and M). OsTRXh1 expression was also observed in the callus (Fig. 2N), indicating that OsTRXh1 is a stress-responsive gene that is widely expressed in rice.
- Knockdown of OsTRXh1 in Rice Causes dwarf and low-tillering Phenotypes: after the formation of the fourth complete leaf, the OsTRXh1 RNAi lines showed a dwarf phenotype as compared with wild-type plants. In 60-d-old OsTRXh1 RNAi plants, the knockdown of OsTRXh1 led to the dwarf and low-tillering phenotypes in the late developmental stages, and the knockdown of OsTRXh1 increases H2O2 levels.
- Knockdown or Overexpression of OsTRXh1 Leads to an ABA-Insensitive Phenotype: the ABA pathway was impaired in the OsTRXh1 overexpression and RNAi lines.
- OsTRXh1 is expressed extensively and is involved in salt and ABA Responses by regulating the apoplastic ROS Accumulation plant growth and development
Subcellular localization
To determine the subcellular localization of OsTRXh1, fluorescently tagged OsTRXh1-YFP (for yellow fluorescent protein) and YFP-OsTRXh1 fusion proteins were transiently expressed in onion (Allium cepa) epidermal cells by particle bombardment. The fluorescence of OsTRXh1-GFP could be detected in the cell wall region, whereas the GFP control was distributed in the intracellular region and could not be detected in the extracellular region. OsTRXh1 is secreted into extracellular regions[2].
Evolution
- A phylogenetic tree was constructed with rice and Arabidopsis h-type Trxs and an N. alata-secreted Trx. OsTRXh1, together with OsTRXh2, OsTRXh3, OsTRXh6, AtTRXh1, AtTRXh3, AtTRXh4, and AtTRXh5, belongs to the h-type Trx subgroup I (Figure 3). The amino acid sequence alignment of OsTRXh1, OsTRXh2, AtTRXh1, AtTRXh3, AtTRXh4, AtTRXh5, and NaTrxh shows that OsTRXh1 has the common structure of Trxs and a conserved redox-active site[2].
- Although h-type Trxs are considered to be mainly cytosolic, some Trx-h are apparently translocated to other compartments(Fig. 4)[4].
knowledge extension
There are ten members of the h-type putative Trxs in rice, and none of them have been clearly characterized yet[1]. In the past ten years, many Trx target proteins have been identified in plants and animals from various organelles, which enhanced our understanding of Trxs[5][6]. OsTRXh1 is a subgroup I h-type Trx in rice and possesses reduction activity in vitro and complements the hydrogen peroxide sensitivity of Trx-deficient yeast mutants. Thioredoxins (Trxs) are small conserved proteins ubiquitously distributed in prokaryotes and eukaryotes. These proteins contain a highly conserved redox-active site (WCGPC) which can reduce the disulfide bonds of target proteins.
Labs working on this gene
- Institute of Molecular and Cell Biology, Hebei Normal University, Shijiazhuang 050016, China
References
- ↑ 1.0 1.1 1.2 are Conserved T. OsTRXh1 regulates the redox state of the apoplast and influences stress responses in rice[J]. signal transduction, 2012, 15: 19.
- ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 Zhang C J, Zhao B C, Ge W N, et al. An apoplastic h-type thioredoxin is involved in the stress response through regulation of the apoplastic reactive oxygen species in rice[J]. Plant physiology, 2011, 157(4): 1884-1899.
- ↑ Xie G, Kato H, Sasaki K, et al. A cold-induced thioredoxin h of rice, OsTrx23, negatively regulates kinase activities of OsMPK3 and OsMPK6 in vitro[J]. FEBS letters, 2009, 583(17): 2734-2738.
- ↑ 4.0 4.1 Hägglund P, Kirkensgaard K G, Maeda K, et al. Molecular Recognition in NADPH-Dependent Plant Thioredoxin Systems—Catalytic Mechanisms, Structural Snapshots and Target Identifications[J]. Advances in Botanical Research, 2009, 52: 461-495.
- ↑ Hisabori T, Hara S, Fujii T, et al. Thioredoxin affinity chromatography: a useful method for further understanding the thioredoxin network[J]. Journal of experimental botany, 2005, 56(416): 1463-1468.
- ↑ Fridlich R, Delalande F, Jaillard C, et al. The thioredoxin-like protein rod-derived cone viability factor (RdCVFL) interacts with TAU and inhibits its phosphorylation in the retina[J]. Molecular & Cellular Proteomics, 2009, 8(6): 1206-1218.
