The NADPH-dependent thioredoxin reductase (NTR)/thioredoxin (Trx) system catalyzes disulfide bond reduction in the cytoplasm and mitochondrion. Trx h is suggested to play an important role in seed development, germination, and seedling growth. Plants have multiple isoforms of Trx h and NTR; however, little is known about the roles of the individual isoforms. Trx h isoforms from barley (Hordeum vulgare) seeds (HvTrxh1 and HvTrxh2) were characterized previously. In this study, two NTR isoforms (HvNTR1 and HvNTR2) were identified, enabling comparison of gene expression, protein appearance, and interaction between individual NTR and Trx h isoforms in barley embryo and aleurone layers. Although mRNA encoding both Trx h isoforms is present in embryo and aleurone layers, the corresponding proteins differed in spatiotemporal appearance. HvNTR2, but not HvNTR1, gene expression seems to be regulated by gibberellic acid. Recombinant HvNTR1 and HvNTR2 exhibited virtually the same affinity toward HvTrxh1 and HvTrxh2, whereas HvNTR2 has slightly higher catalytic activity than HvNTR1 with both Trx h isoforms, and HvNTR1 has slightly higher catalytic activity toward HvTrxh1 than HvTrxh2. Notably, both NTRs reduced Trx h at the acidic conditions residing in the starchy endosperm during germination. Interspecies reactions between the barley proteins and Escherichia coli Trx or Arabidopsis thaliana NTR, respectively, occurred with 20- to 90-fold weaker affinity. This first investigation of regulation and interactions between members of the NTR/Trx system in barley seed tissues suggests that different isoforms are differentially regulated but may have overlapping roles, with HvNTR2 and HvTrxh1 being the predominant isoforms in the aleurone layer.

Although overexpression of tHMG1 and downregulation of ERG9 enhanced linalool titers threefold in the engineered yeast strain, alleviating linalool toxicity is necessary for further improvement of linalool biosynthesis in yeast.

The cereal aleurone layer is of major importance due to its nutritional properties as well as its central role in seed germination and industrial malting. Cereal seed germination involves mobilisation of storage reserves in the starchy endosperm to support seedling growth. In response to gibberellic acid produced by the embryo, the aleurone layer synthesises hydrolases that are secreted to the endosperm for the degradation of storage products. The barley aleurone layer can be separated from the other seed tissues and maintained in culture, allowing the study of the effect of added signalling molecules in an isolated system. These properties have led to its use as a model system for the study of plant signalling and germination. More recently, proteome analysis of the aleurone layer has provided new insight into this unique tissue including identification of plasma membrane proteins and targeted analysis of germination-related changes and the thioredoxin system. Here, analysis of intracellular and secreted proteomes reveals features of the aleurone layer system that makes it promising for investigations of plant protein secretion mechanisms.

[Pd(4-OHPh-tpy)Cl]Cl was prepared. The complex interacts with DNA via a combination of covalent, intercalation, and hydrogen bonding interactions.

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Metallothioneins (MTs) are ubiquitous, low molecular mass and cysteine-rich proteins that play important roles in maintaining intracellular metal homeostasis, eliminating metal toxification and protecting the cells against oxidative damages. MTs are able to bind metal ions through the thiol groups of their cysteine residues. Plants have several MT isoforms which are classified into four types based on the arrangement of cysteine residues. In the present study, a rice (Oryza sativa) gene encoding type 1 MT isoform, OsMTI-1b, was inserted in vector pET41a and overexpressed in Escherichia coli as carboxy-terminal extensions of glutathione-S-transferase (GST). The recombinant protein GST-OsMTI-1b was purified using affinity chromatography and its ability to bind with Ni(2+), Cd(2+), Zn(2+) and Cu(2+) ions was analyzed. The results demonstrated that this isoform has ability to bind Ni(2+), Cd(2+) and Zn(2+) ions in vitro, whereas it has no substantial ability to bind Cu(2+) ions. From competitive reaction with 5,5'-dithiobis(2-nitrobenzoic acid), DTNB, the affinity of metal ions for recombinant form of GST-OsMTI-1b was as follows: Ni(2+)/Cd(2+) > Zn(2+) > Cu(2+).

Metallothioneins (MTs) are a superfamily of low-molecular-weight, cysteine (Cys)-rich proteins that are believed to play important roles in protection against metal toxicity and oxidative stress. Plants have several MT isoforms, which are classified into four types based on the arrangement of Cys residues. In this study, two rice (Oryza sativa) MT isoforms, OsMTI-1b and OsMTII-1a from type 1 and type 4, respectively, were heterologously expressed in Escherichia coli as carboxy-terminal extensions of glutathione-S-transferase (GST). Transformed cells expressing GST-OsMTI-1b showed increased tolerance to Ni(2+) , Cd(2+) , and Zn(2+) and accumulated more metal ions compared with cells expressing GST alone. However, heterologous expression of GST-OsMTII-1a had no significant effects on metal tolerance or ion accumulation. The UV absorption spectra and competitive reactions of in vitro Cd-incubated proteins with 5-5'-dithiobis(2-nitrobenzoic) acid revealed that GST-OsMTI-1b, but not GST-OsMTII-1a, is able to form Cd-thiolate clusters. Furthermore, heterologous expression of both GST-OsMTI-1b and GST-OsMTII-1a conferred H2 O2 tolerance to E. coli cells. Taken together, the results presented here show that two different rice MT isoforms belonging to type 1 and type 4 differ in Ni(2+) , Cd(2+) , and Zn(2+) binding abilities, but they may have overlapping function in protection of cells against oxidative stress.