Proteomic analysis of copper stress responses in the roots of two rice (Oryza sativa L.) varieties differing in Cu tolerance

Background and aims

Copper (Cu) is an essential micronutrient required for growth and development of plants. However, excess Cu is toxic to plants. To understand the mechanisms involved in copper stress response, a proteomic approach was used to investigate the differences in Cu stress-induced protein expression between a Cu-tolerant variety (B1139) and a Cu-sensitive one (B1195) of rice.

Methods

Rice seedlings were exposed to 8 μM Cu for 3 days, with plants grown in the normal nutrient solution containing 0.32 μM Cu serving as the control. Proteins were extracted from the roots and separated by two-dimensional PAGE. Thirty four proteins were identified using MALDI-TOF mass spectrometry.

Results

Thirty-four protein spots were found to be differently expressed in the Cu-stressed roots in at least one variety of rice, including those involved in antioxidative defense, redox regulation, stress response, sulfur and glutathione (GSH) metabolism, carbohydrate metabolism, signal transduction, and some other proteins with various functions. Nine proteins, including putative cysteine synthase, probable serine acetyltransferase 3, L-ascorbate peroxidase 1, putative glutathione S-transferase 2, and thioredoxin-like 3-3, exhibited a greater increase in response to Cu stress in the Cu-tolerant variety B1139 compared with the Cu–sensitive variety B1195.

Conclusion

The majority of the proteins showing differential expression in response to Cu exposure are involved in the redox regulation, and sulfur and GSH metabolism, suggesting that these proteins, together with antioxidant enzymes, play an important role in the detoxification of excess Cu and maintaining cellular homeostasis.     

Converting paddy fields to Lei bamboo (Phyllostachys praecox) stands affected soil nutrient concentrations, labile organic carbon pools, and organic carbon chemical compositions

Background and aims

Land-use change often markedly alters soil carbon (C) and nitrogen (N) pool sizes with implications for climate change and soil sustainability. The objective of this research was to study the effect of converting paddy fields to Lei bamboo (Phyllostachys praecox) stands on soil C and N and other nutrient pools as well as the chemical structure of soil organic C (SOC) in the soil profile.

Methods

Soils (Anthrosols) from four adjacent paddy field–bamboo forest pairs with a known land-use history were sampled from Lin’an County, Zhejiang Province. Soil water soluble organic C (WSOC), hot water soluble organic C (HWSOC), microbial biomass C (MBC), readily oxidizable C (ROC), water soluble organic N (WSON), and other soil chemical and physical properties were determined. Soil organic C functional group compositions were determined by ¹³C-nuclear magnetic resonance (NMR).

Results

Concentrations of soil available P, available K, and different N forms increased (P?<?0.05) by the land-use conversion. Higher concentrations of SOC and total N (TN) were observed in the subsoil (20–40 and 40–60 cm soil layers) but not in the topsoil (0–20 cm layer) in the bamboo stands than in the paddy fields. The storage of SOC and TN in the entire soil profile (0–60 cm) increased by 56.7 and 70.7 %, respectively, after the land-use change. The increases in the SOC stock of the three soil layers were 11.0, 14.3, and 9.5 Mg C ha^?1, respectively. The conversion decreased WSOC concentrations in the subsoil but increased the ROC concentration in the topsoil. Solid-state NMR spectroscopy of soil samples showed that the conversion increased (P?<?0.05) the O-alkyl C content while decreased the aromatic C content, alkyl C to O-alkyl C ratio (A/O-A), and aromaticity of SOC.

Conclusions

Conversion of paddy fields to bamboo stands increased soil nutrient availability, and SOC and TN stocks. Effects of land-use change on C pools and C chemistry of SOC varied among different soil layers in the profile. The impact of the land-use conversion on soil organic C pools was not restricted to the topsoil, but changes in the subsoil were equally large and should be accounted for.     

Activity of the Arabidopsis RD29A and RD29B promoter elements in soybean under water stress

The constitutive and drought-induced activities of the Arabidopsis thaliana RD29A and RD29B promoters were monitored in soybean (Glycine max (L.) Merr.] via fusions with the visual marker gene β-glucuronidase (GUS). Physiological responses of soybean plants were monitored over 9 days of water deprivation under greenhouse conditions. Data were used to select appropriate time points to monitor the activities of the respective promoter elements. Qualitative and quantitative assays for GUS expression were conducted in root and leaf tissues, from plants under well-watered and dry-down conditions. Both RD29A and RD29B promoters were significantly activated in soybean plants subjected to dry-down conditions. However, a low level of constitutive promoter activity was also observed in both root and leaves of plants under well-watered conditions. GUS expression was notably higher in roots than in leaves. These observations suggest that the respective drought-responsive regulatory elements present in the RD29X promoters may be useful in controlling targeted transgenes to mitigate abiotic stress in soybean, provided the transgene under control of these promoters does not invoke agronomic penalties with leaky expression when no abiotic stress is imposed.     

Selection of Drug-Resistant Feline Immunodeficiency Virus (FIV) Encoding FIV/HIV Chimeric Protease in the Presence of HIV-Specific Protease Inhibitors

An infectious chimeric feline immunodeficiency virus (FIV)/HIV strain carrying six HIV-like protease (PR) mutations (I37V/N55M/V59I/I98S/Q99V/P100N) was subjected to selection in culture against the PR inhibitor lopinavir (LPV), darunavir (DRV), or TL-3. LPV selection resulted in the sequential emergence of V99A (strain S-1X), I59V (strain S-2X), and I108V (strain S-3X) mutations, followed by V37I (strain S-4X). Mutant PRs were analyzed in vitro, and an isogenic virus producing each mutant PR was analyzed in culture for LPV sensitivity, yielding results consistent with the original selection. The 50% inhibitory concentrations (IC₅₀s) for S-1X, S-2X, S-3X, and S-4X were 95, 643, 627, and 1,543 nM, respectively. The primary resistance mutations, V99⁸²A, I59⁵⁰V, and V37³²I, are consistent with the resistance pattern developed by HIV-1 under similar selection conditions. While resistance to LPV emerged readily, similar PR mutations causing resistance to either DRV or TL-3 failed to emerge after passage for more than a year. However, a G37D mutation in the nucleocapsid (NC) was observed in both selections and an isogenic G37D mutant replicated in the presence of 100 nM DRV or TL-3, whereas parental chimeric FIV could not. An additional mutation, L92V, near the PR active site in the folded structure recently emerged during TL-3 selection. The L92V mutant PR exhibited an IC₅₀ of 50 nM, compared to 35 nM for 6s-98S PR, and processed the NC-p2 junction more efficiently, consistent with increased viral fitness. These findings emphasize the role of mutations outside the active site of PR in increasing viral resistance to active-site inhibitors and suggest additional targets for inhibitor development.     

Luteolin attenuates TGF-β1-induced epithelial–mesenchymal transition of lung cancer cells by interfering in the PI3K/Akt–NF-κB–Snail pathway

Aims

Luteolin is a natural flavonoid that possesses a variety of pharmacological activities, such as anti-inflammatory and anti-cancer abilities. Whether luteolin regulates the transformation ability of lung cancer cells remains unclear. The current study aims to uncover the effects and underlying mechanisms of luteolin in regulation of and epithelial–mesenchymal transition of lung cancer cells.

Main methods

The lung adenocarcinoma A549 cells were used in this experiment; the cells were pretreated with luteolin followed by administration with TGF-β1. The expression levels of various cadherin and related upstream regulatory modules were examined.

Key findings

Pretreatment of luteolin prevented the morphological change and downregulation of E-cadherin of A549 cells induced by TGF-β1. In addition, the activation of PI3K–Akt–IκBa–NF-κB–Snail pathway which leads to the decline of E-cadherin induced by TGF-β1 was also attenuated under the pretreatment of luteolin.

Significance

We provide the mechanisms about how luteolin attenuated the epithelial–mesenchymal transition of A549 lung cancer cells induced by TGF-β1. This finding will strengthen the anti-cancer effects of flavonoid compounds via the regulation of migration/invasion and EMT ability of various cancer cells.     

Malleola tibetica sp. nov. (Aeridinae,Orchidaceae) from Tibet,China

Malleola tibetica, a new species from southeastern tropical Tibet, China, is described and illustrated. Morphologically, the new species is closely related to M. dentifera, but differs from it by having uniformly green leaves, flowers with entire lateral lobes of the lip and a basally thickened mid‐lobe, and a column that is densely cristaline‐papillose adaxially.     

Metabolic engineering strategies for improving xylitol production from hemicellulosic sugars

Xylitol is a five-carbon sugar alcohol with potential for use as a sweetener. Industrially, xylitol is currently produced by chemical hydrogenation of d-xylose using Raney nickel catalysts and this requires expensive separation and purification steps as well as high pressure and temperature that lead to environmental pollution. Highly efficient biotechnological production of xylitol using microorganisms is gaining more attention and has been proposed as an alternative process. Although the biotechnological method has not yet surpassed the advantages of chemical reduction in terms of yield and cost, various strategies offer promise for the biotechnological production of xylitol. In this review, the focus is on the most recent developments of the main metabolic engineering strategies for improving the production of xylitol.     

Cooperation between osteoblastic cells and endothelial cells enhances their phenotypic responses and improves osteoblast function

Osteogenesis requires close co-operation with angiogenesis to create vascularized bone tissue. In this study, an indirect co-culture model using osteoblasts (OBs), primary endothelial cells (ECs) and Matrigel interlayer was established to understand the impact of each cell type on the other. ECs synergistically enhanced osteoblastic gene expression by OBs, while OBs were capable of supporting tubule-like structures formed by ECs on Matrigel, enhancing mean tubule length from 146.5 ± 23.5 μm in ECs alone to 192 ± 28.6 μm in co-culture (p < 0.05). Similar improvements were noted in terms of tubule number. An applicability study of the co-culture model to bone tissue engineering, performed on a biopolymer fibrous membrane, showed substantially enhanced deposition of calcified nodules. These results demonstrate the efficacy of co-culture with ECs to improve osteogenesis for bone tissue engineering.     

A role for Ethylene-Insensitive3 in the regulation of hydrogen peroxide production during seed germination under high salinity in Arabidopsis

The Arabidopsis Ethylene-Insensitive3 (EIN3) has received attention recently and has been shown to be involved in the regulation of multitude of responses ranging from biotic stress defense and development to hormone interaction. To better understand the roles of EIN3 in plants response to salinity stress during germination and post-germination development, seeds of two EIN3 deficient mutant and a EIN3 overexpression mutant of Arabidopsis were analyzed under salinity and compared with Col-0 as control. The results showed that the ein3-1eil1-1 double mutant (lacking EIN3 and EIN3-Like1) and ein3-1 (lacking EIN3) were hypersensitive to high salinity (>150 mM NaCl), while EIN3 overexpression mutant (EIN3ox) displayed enhanced tolerance, indicating that EIN3 plays important roles during seed germination under salinity. In addition, we also found that the two EIN3 deficient mutant seedlings accumulate high levels of hydrogen peroxide (H₂O₂), which was thought to be an inhibitor of germination under salinity before, suggesting that EIN3 may function as a negative regulator of reactive oxygen species metabolism in germinating seeds under salinity. Taken together, our studies provide insights that EIN3 promotes seed germination under salinity, at least in part, through modulating concentration of H₂O₂ in germinating seeds.