Cadmium reduces zinc uptake but enhances its translocation in the cadmium-accumulator, <Emphasis Type="Italic">Carpobrotus rossii</Emphasis>, without affecting speciation

Background and aims

Interactions between Cd and Zn occur in soils and plants but are inconsistent. This study examined how Cd/Zn interactions influence the growth of Carpobrotus rossii (Haw.) and the accumulation of Cd and Zn in plants.

Methods

Plants were grown in nutrient solutions containing 5–100 μM Zn and 0, 5 or 15 μM Cd. Plant growth and tissue concentrations were measured, and the speciation of Zn within the plant tissues determined using synchrotron-based X-ray absorption spectroscopy.

Results

There was an additive negative interaction between Cd and Zn on root growth. Only the highest level of Zn (100 μM) decreased Cd concentrations in root and shoot tissues (by 40–64%), whilst 100 μM Zn enhanced Cd translocation at 5 μM Cd but decreased it at 15 μM Cd. In contrast, both 5 and 15 μM Cd decreased Zn concentrations in root and shoot tissues but increased Zn translocation by 30–90%. This interaction was not associated with changes in Zn speciation within the plants, with most Zn associated with oxalate (48–87%).

Conclusions

The presence of Zn and Cd resulted in an additive negative effect on root growth, but an antagonistic pattern in their accumulation in shoots of C. rossii.

     

Catesbeianin-1, a novel antimicrobial peptide isolated from the skin of <Emphasis Type="Italic">Lithobates catesbeianus</Emphasis> (American bullfrog)

Objectives

To identify and characterize a novel antimicrobial peptide, catesbeianin-1.

Results

Catesbeianin-1 is 25 amino acids long and is α-helical, cationic and amphipathic. It had antimicrobial activity against Gram-positive and Gram-negative bacteria. It was resistant against trypsin and pepsin. Catesbeianin-1 exhibited moderate hemolytic activity (approx 8%) at 100 μg/ml, and its HC₅₀ (50% hemolytic concentration) was 300 μg/ml. Its cytotoxicity was approx 10–20% at 100 μg/ml, and its CC₅₀ (50% cytotoxic concentration) was >100 μg/ml. The LD₅₀ of catesbeianin-1 in mice was 80 mg/kg. At 3.1 µg/ml, catesbeianin-1 significantly inhibited the growth of methicillin-resistant Staphylococcus aureus.

Conclusions

A new antimicrobial peptide from the skin of Lithobates catesbeianus (American bullfrog) may represent a template for the development of novel antimicrobial agents.

     

Asymmetric effects of litter removal and litter addition on the structure and function of soil microbial communities in a managed pine forest

Aims

The effect of different MeJA doses applied prior to or simultaneously with toxic Al on biochemical and physiological properties of Vaccinium corymbosum cultivars with contrasting Al resistance was studied.

Methods

Legacy (Al-resistant) and Bluegold (Al-sensitive) plants were treated with and without toxic Al under controlled conditions: a) without Al and MeJA, b) 100 μM Al, c) 100 μM Al + 5 μM MeJA, d) 100 μM Al + 10 μM MeJA and e) 100 μM Al + 50 μM MeJA. MeJA was applied to leaves 24 h prior to or simultaneously with Al in nutrient solution. After 48 h, Al-concentration, lipid peroxidation (LP), H₂O₂, antioxidant activity, total phenols, total flavonoids, phenolic compounds and superoxide dismutase activity (SOD) of plant organs were analyzed.

Results

Al-concentrations increased with Al-treatment in both cultivars, being Al, LP and H₂O₂ concentrations reduced with low simultaneous MeJA application. Higher MeJA doses induced more oxidative damage than the lowest. Legacy increased mainly non-enzymatic compounds, whereas Bluegold increased SOD activity to counteract Al³⁺.

Conclusions

Low MeJA doses applied simultaneously with Al³⁺ increased Al-resistance in Legacy by increasing phenolic compounds, while Bluegold reduced oxidative damage through increment of SOD activity, suggesting a diminution of its Al-sensitivity. Higher MeJA doses could be potentially toxic. Studies are needed to determine the molecular mechanisms involved in the protective MeJA effect against Al-toxicity.

     

Mitofusin 1 is degraded at G<Subscript>2</Subscript>/M phase through ubiquitylation by MARCH5

Background

Mitochondria exhibit a dynamic morphology in cells and their biogenesis and function are integrated with the nuclear cell cycle. In mitotic cells, the filamentous network structure of mitochondria takes on a fragmented form. To date, however, whether mitochondrial fusion activity is regulated in mitosis has yet to be elucidated.

Findings

Here, we report that mitochondria were found to be fragmented in G₂ phase prior to mitotic entry. Mitofusin 1 (Mfn1), a mitochondrial fusion protein, interacted with cyclin B1, and their interactions became stronger in G₂/M phase. In addition, MARCH5, a mitochondrial E3 ubiquitin ligase, reduced Mfn1 levels and the MARCH5-mediated Mfn1 ubiquitylation were enhanced in G₂/M phase.

Conclusions

Mfn1 is degraded through the MARCH5-mediated ubiquitylation in G₂/M phase and the cell cycle-dependent degradation of Mfn1 could be facilitated by interaction with cyclin B1/Cdk1 complexes.

     

Elevated CO<Subscript>2</Subscript> and virus infection impacts wheat and aphid metabolism

Introduction

The aphid Rhopalosiphum padi L. is a vector of Barley yellow dwarf virus (BYDV) in wheat and other economically important cereal crops. Increased atmospheric CO₂ has been shown to alter plant growth and metabolism, enhancing BYDV disease in wheat. However, the biochemical influences on aphid metabolism are not known.

Objectives

This work aims to determine whether altered host-plant quality, influenced by virus infection and elevated CO₂, impacts aphid weight and metabolism.

Methods

Untargeted ¹H NMR metabolomics coupled with multivariate statistics were employed to profile the metabolism of R. padi reared on virus-infected and non-infected (sham-inoculated) wheat grown under ambient CO₂ (aCO₂, 400 µmol mol^?1) and future, predicted elevated CO₂ (eCO₂, 650 µmol mol^?1) concentrations. Un-colonised wheat was also profiled to observe changes to host-plant quality (i.e., amino acids and sugars).

Results

The direct impacts of virus or eCO₂ were compared. Virus presence increased aphid weight under aCO₂ but decreased weight under eCO₂; whilst eCO₂ increased non-viruliferous (sham) aphid weight but decreased viruliferous aphid weight. Discriminatory metabolites due to eCO₂ were succinate and sucrose (in sham wheat), glucose, choline and betaine (in infected wheat), and threonine, lactate, alanine, GABA, glutamine, glutamate and asparagine (in aphids), irrespective of virus presence. Discriminatory metabolites due to virus presence were alanine, GABA, succinate and betaine (in wheat) and threonine and lactate (in aphids), irrespective of CO₂ treatment.

Conclusion

This study confirms that virus and eCO₂ alter host-plant quality, and these differences are reflected by aphid weight and metabolism.

     

Engineering a glycerol utilization pathway in Corynebacterium glutamicum for succinate production under O<Subscript>2</Subscript> deprivation

Objective

To explore the glycerol utilization pathway in Corynebacterium glutamicum for succinate production under O₂ deprivation.

Result

Overexpression of a glycerol facilitator, glycerol dehydrogenase and dihydroxyacetone kinase from Escherichia coli K-12 in C. glutamicum led to recombinant strains NC-3G diverting glycerol utilization towards succinate production under O₂ deprivation. Under these conditions, strain NC-3G efficiently consumed glycerol and produced succinate without growth. The recombinant C. glutamicum utilizing glycerol as the sole carbon source showed higher intracellular NADH/NAD⁺ ratio compare with utilizing glucose. The mass conversion of succinate increased from 0.64 to 0.95. Using an anaerobic fed-batch fermentation process, the final strain produced 38.4 g succinate/l with an average yield of 1.02 g/g.

Conclusions

The metabolically-engineered strains showed an efficient succinate production using glycerol as sole carbon source under O₂ deprivation.

     

Endophytic infection modifies organic acid and mineral element accumulation by rice under Na<Subscript>2</Subscript>CO<Subscript>3</Subscript> stress

Background and aims

Saline and alkali soils severely impact plant growth. Endophyte and plant associations are known to significantly modify plant metabolism. This study reports the effects of a type of endophyte on organic acid (OA) accumulation and ionic balance in rice under Na₂CO₃ stress.

Methods

Rice seedlings with (E+) and without (E-) endophytic infection were subjected to different levels of Na₂CO₃ stress (0, 5, 10, 15, and 20 mM) for two weeks. Organic acids and mineral elements in the leaves and roots were determined.

Results

Seedlings with endophytic infection accumulated mainly citrate and fumarate, with some malate and succinate in the leaves. In the roots, accumulation of malate and fumarate was enhanced significantly by endophytic infection, while less citrate and succinate was accumulated under Na₂CO₃ stress, which suggested that leaves and roots use different mechanisms to control OA metabolism. Endophytes reduced the total Na and Na:K ratios, but increased ST values, the percent changes of other measured nutrients, Chl content, and dry weight per plant under Na₂CO₃ stress.

Conclusions

Endophytic infection plays a key role in maintaining plant growth by improving nutrient uptake and adjusting OA accumulation under Na₂CO₃ stress. The application of endophytes can enhance the resistance of rice to salinity.

     

Rapid and efficient degradation of bisphenol A by chloroperoxidase from <Emphasis Type="Italic">Caldariomyces fumago</Emphasis>: product analysis and ecotoxicity evaluation of the degraded solution

Objectives

To degrade enzymatically bisphenol A (BPA) that causes serious environmental concerns and is difficult to be degraded by chemical or physical methods.

Results

BPA (150 mg l^?1) was completely degraded by chloroperoxidase (CPO)/H₂O₂ within 7 min at room temperature, atmospheric pressure with the enzyme at 6 μg CPO ml^?1. The degradation products were identified by HPLC–MS, which suggested involvement of multiple steps. Enzymatic treatment followed by existing bioremediation technologies (activated sludge) enhanced removal of COD from 9 to 54 %. Using an ecotoxicity evaluation with Chlorella pyrenoidosa, the degradation products had a lower toxicity than BPA.

Conclusion

BPA can be degraded rapidly and efficiently under mild conditions with chloroperoxidase at 6 μg ml^?1. The degradation products had a lower toxicity than BPA.

     

Reengineering substrate specificity of <Emphasis Type="Italic">E. coli</Emphasis> glutamate dehydrogenase using a position-based prediction method

Objective

To re-engineer the active site of proteins for non-natural substrates using a position-based prediction method (PBPM).

Results

The approach has been applied to re-engineer the E. coli glutamate dehydrogenase to alter its substrate from glutamate to homoserine for a de novo 1,3-propanediol biosynthetic pathway. After identification of key residues that determine the substrate specificity, residue K92 was selected as a candidate site for mutation. Among the three mutations (K92V, K92C, and K92M) suggested by PBPM, the specific activity of the best mutant (K92 V) was increased from 171 ± 35 to 1328 ± 71 μU mg^?1.

Conclusion

The PBPM approach has a high efficiency for re-engineering the substrate specificity of natural enzymes for new substrates.

     

Characterization of H<Subscript>2</Subscript> photoproduction by marine green alga <Emphasis Type="Italic">Tetraselmis subcordiformis</Emphasis> integrated with an alkaline fuel cell

Objectives

To investigate the feasibility of coupling carbonyl cyanide m-chlorophenylhydrazone-regulated photohydrogen production by Tetraselmis subcordiformis in a photobioreactor to an alkaline fuel cell (AFC).

Results

H₂ evolution kinetics in the AFC integrated process was characterized. The duration of H₂ evolution was prolonged and its yield was improved about 1.5-fold (to 78 ± 5 ml l^?1) compared with that of the process without AFC. Improved H₂ yield was possibly caused by removal of H₂ feedback inhibition by H₂ consumption in situ. Decreases in the H₂ production rate correlated with the gradual deactivation of PSII and hydrogenase activities. The H₂ yield was closely associated with catabolism of starch and protein.

Conclusion

A marine green algal CO₂-supplemented culture integrated with in situ H₂-consumption by an AFC system was developed as a viable protocol for the H₂ production.

     

Pharmacological characterization of GABA<Subscript>A</Subscript> receptors in taurine-fed mice

Background

Taurine is one of the most abundant free amino acids especially in excitable tissues, with wide physiological actions. Chronic supplementation of taurine in drinking water to mice increases brain excitability mainly through alterations in the inhibitory GABAergic system. These changes include elevated expression level of glutamic acid decarboxylase (GAD) and increased levels of GABA. Additionally we reported that GABA_A receptors were down regulated with chronic administration of taurine. Here, we investigated pharmacologically the functional significance of decreased / or change in subunit composition of the GABA_A receptors by determining the threshold for picrotoxin-induced seizures. Picrotoxin, an antagonist of GABA_A receptors that blocks the channels while in the open state, binds within the pore of the channel between the β2 and β3 subunits. These are the same subunits to which GABA and presumably taurine binds.

Methods

Two-month-old male FVB/NJ mice were subcutaneously injected with picrotoxin (5 mg kg^-1) and observed for a) latency until seizures began, b) duration of seizures, and c) frequency of seizures. For taurine treatment, mice were either fed taurine in drinking water (0.05%) or injected (43 mg/kg) 15 min prior to picrotoxin injection.

Results

We found that taurine-fed mice are resistant to picrotoxin-induced seizures when compared to age-matched controls, as measured by increased latency to seizure, decreased occurrence of seizures and reduced mortality rate. In the picrotoxin-treated animals, latency and duration were significantly shorter than in taurine-treated animas. Injection of taurine 15 min before picrotoxin significantly delayed seizure onset, as did chronic administration of taurine in the diet. Further, taurine treatment significantly increased survival rates compared to the picrotoxin-treated mice.

Conclusions

We suggest that the elevated threshold for picrotoxin-induced seizures in taurine-fed mice is due to the reduced binding sites available for picrotoxin binding due to the reduced expression of the beta subunits of the GABA_A receptor. The delayed effects of picrotoxin after acute taurine injection may indicate that the two molecules are competing for the same binding site on the GABA_A receptor. Thus, taurine-fed mice have a functional alteration in the GABAergic system. These include: increased GAD expression, increased GABA levels, and changes in subunit composition of the GABA_A receptors. Such a finding is relevant in conditions where agonists of GABA_A receptors, such as anesthetics, are administered.

     

The effect of 1,25-dihydroxyvitamin D<Subscript>3</Subscript> on TSLP,IL-33 and IL-25 expression in respiratory epithelium

Background

Airway epithelium is an active and important component of the immunological response in the pathophysiology of obstructive lung diseases. Recent studies suggest an important role for vitamin D₃ in asthma severity and treatment response.

Objective

Our study evaluated the influence of an active form of vitamin D₃ on the expression of selected mediators of allergic inflammation in the respiratory epithelium.

Material and Methods

Primary nasal and bronchial epithelial cells were exposed to1,25D₃ for 1 hour and were then stimulated or not with IL-4, TNF-α, LPS, and poly I:C. After 24 hours TSLP, IL-33, and IL-25 protein levels were measured in culture supernatants usingELISAandmRNAlevels in cells by real time PCR.

Results

1,25D₃ increased TSLP concentration in unstimulated nasal epithelial cells, but did not influence IL-33 and IL-25 expression. In IL-4-stimulated epithelial cell cultures 1,25D₃ mostly inhibited TSLP and IL-33 expression. In LPS-treated cultures 1,25D₃ decreased IL-33 expression. Simultaneously 1,25D₃ augmented IL-25 production in the same model of stimulation.

Conclusion

Our study revealed the dual nature of vitamin D₃ manifested in both pro- and anti-inflammatory properties observed in airway epithelial cells.

     

Relationships between nitrogen,dry matter accumulation and glucosinolates in <Emphasis Type="Italic">Eruca sativa</Emphasis> Mills. The applicability of the critical NO<Subscript>3</Subscript>-N levels approach

Background and Aims

Rocket salad (Eruca sativa Mills) is one of the major leafy vegetables produced worldwide and has been characterized as a rich source of chemoprotective glucosinolates (GSL). The relationship between N fertilization and the resulting plant biomass and N status with GSL quantity and quality in rocket leaves was examined.

Methods

A pot experiment was conducted, applying ten different N-rates and destructive sampling was carried out 15, 30 and 45 days after transplanting (DAT). The Mitscherlich equation was used to establish NO₃-N critical levels at each growth stage and as an indicator of N demand for relative maximum dry matter accumulation and glucosinolate content and composition was determined.

Results

Glucosinolate content was significantly influenced by N rate, growth stage and their interaction. Different GSL types showed dissimilar responses to N fertilization: aliphatic GSLs were significantly reduced under increased N rates whereas indole GSL showed the reverse. Under excess N fertilization (>1.04 g/plant), dry matter accumulation remained constant, NO₃-N was significantly increased and total GSL content was significantly reduced, factors that could lead to an anticipated product quality decline.

Conclusions

The application of the critical NO₃-N level approach used to identify optimal N fertilization rates for plant growth could serve as means to obtain optimized GSL content in the edible plant parts.

     

Exogenous H<Subscript>2</Subscript>S restores ischemic post-conditioning-induced cardioprotection through inhibiting endoplasmic reticulum stress in the aged cardiomyocytes

Background

A gasotransmitter hydrogen sulfide (H₂S) plays an important physiological and pathological role in cardiovascular system. Ischemic post-conditioning (PC) provides cardioprotection in the young hearts but not in the aged hearts. Exogenous H₂S restores PC-induced cardioprotection by inhibition of mitochondrial permeability transition pore opening and oxidative stress and increase of autophagy in the aged hearts. However, whether H₂S contributes to the recovery of PC-induced cardioprotection via down-regulation of endoplasmic reticulum stress (ERS) in the aged hearts is unclear.

Methods

The aged H9C2 cells (the cardiomyocytes line) were induced using H₂O₂ and were exposed to H/R and PC protocols. Cell viability was observed by CCK-8 kit. Apoptosis was detected by Hoechst 33342 staining and flow cytometry. Related protein expressions were detected through Western blot.

Results

In the present study, we found that 30 μM H₂O₂ induced H9C2 cells senescence but not apoptosis. Supplementation of NaHS protected against H/R-induced apoptosis, the expression of cleaved caspase-3 and cleaved caspase-9 and the release of cytochrome c. The addition of NaHS also counteracted the reduction of cell viability caused by H/R and decreased the expression of GRP 78, CHOP, cleaved caspase-12, ATF 4, ATF 6 and XBP-1 and the phosphorylation of PERK, eIF 2α and IRE 1α. Additionally, NaHS increased Bcl-2 expression. PC alone did not provide cardioprotection in H/R-treated aged cardiomyocytes, which was significantly restored by the supplementation of NaHS. The beneficial role of NaHS was similar to the supply of 4-PBA (an inhibitor of ERS), GSK2656157 (an inhibitor of PERK), STF083010 (an inhibitor of IRE 1α), respectively, during PC.

Conclusion

Our results suggest that the recovery of myocardial protection from PC by exogenous H₂S is associated with the inhibition of ERS via down-regulating PERK-eIF 2α-ATF 4, IRE 1α-XBP-1 and ATF 6 pathways in the aged cardiomyocytes.

     

CaCO<Subscript>3</Subscript> supplementation alleviates the inhibition of formic acid on acetone/butanol/ethanol fermentation by <Emphasis Type="Italic">Clostridium acetobutylicum</Emphasis>

Objective

To investigate the inhibiting effect of formic acid on acetone/butanol/ethanol (ABE) fermentation and explain the mechanism of the alleviation in the inhibiting effect under CaCO₃ supplementation condition.

Results

From the medium containing 50 g sugars l^?1 and 0.5 g formic acid l^?1, only 0.75 g ABE l^?1 was produced when pH was adjusted by KOH and fermentation ended prematurely before the transformation from acidogenesis to solventogenesis. In contrast, 11.4 g ABE l^?1 was produced when pH was adjusted by 4 g CaCO₃ l^?1. The beneficial effect can be ascribed to the buffering capacity of CaCO₃. Comparative analysis results showed that the undissociated formic acid concentration and acid production coupled with ATP and NADH was affected by the pH buffering capacity of CaCO₃. Four millimole undissociated formic acid was the threshold at which the transformation to solventogenesis occurred.

Conclusion

The inhibiting effect of formic acid on ABE fermentation can be alleviated by CaCO₃ supplementation due to its buffering capacity.

     

A high effective NADH-ferricyanide dehydrogenase coupled with laccase for NAD<Superscript>+</Superscript> regeneration

Objectives

To find an efficient and cheap system for NAD⁺ regeneration

Results

A NADH-ferricyanide dehydrogenase was obtained from an isolate of Escherichia coli. Optimal activity of the NADH dehydrogenase was at 45 °C and pH 7.5, with a K _m value for NADH of 10 μM. By combining the NADH dehydrogenase, potassium ferricyanide and laccase, a bi-enzyme system for NAD⁺ regeneration was established. The system is attractive in that the O₂ consumed by laccase is from air and the sole byproduct of the reaction is water. During the reaction process, 10 mM NAD⁺ was transformed from NADH in less than 2 h under the condition of 0.5 U NADH dehydrogenase, 0.5 U laccase, 0.1 mM potassium ferricyanide at pH 5.6, 30 °C

Conclusion

The bi-enzyme system employed the NADH-ferricyanide dehydrogenase and laccase as catalysts, and potassium ferricyanide as redox mediator, is a promising alternative for NAD⁺ regeneration.

     

Low flow extracorporeal CO<Subscript>2</Subscript> removal in ARDS patients: a prospective short-term crossover pilot study

Background

Lung protective mechanical ventilation (MV) is the corner stone of therapy for ARDS. However, its use may be limited by respiratory acidosis.This study explored feasibility of, effectiveness and safety of low flow extracorporeal CO₂ removal (ECCO₂R).

Methods

This was a prospective pilot study, using the Abylcap® (Bellco) ECCO₂R, with crossover off-on-off design (2-h blocks) under stable MV settings, and follow up till end of ECCO₂R. Primary endpoint for effectiveness was a 20% reduction of PaCO₂ after the first 2-h. Adverse events (AE) were recorded prospectively.We included 10 ARDS patients on MV, with PaO₂/FiO₂?<?150 mmHg, tidal volume?≤?8 mL/kg with positive end-expiratory pressure ≥?5 cmH₂O, FiO₂ titrated to SaO₂ 88–95%, plateau pressure ≥?28 cmH₂O, and respiratory acidosis (pH <7.25).

Results

After 2-h of ECCO₂R, 6 patients had a ≥?20% decrease in PaCO₂ (60%); PaCO₂ decreased 28.4% (from 58.4 to 48.7 mmHg, p?=?0.005), and pH increased (1.59%, p?=?0.005). ECCO₂R was hemodynamically well tolerated. During the whole period of ECCO₂R, 6 patients had an AE (60%); bleeding occurred in 5 patients (50%) and circuit thrombosis in 3 patients (30%), these were judged not to be life threatening.

Conclusions

In ARDS patients, low flow ECCO₂R significantly reduced PaCO₂ after 2 h, Follow up during the entire ECCO₂R period revealed a high incidence of bleeding and circuit thrombosis.

Trial registration

https://clinicaltrials.gov identifier: NCT01911533, registered 23 July 2013.

     

Differential elemental uptake in three pseudo-metallophyte C<Subscript>4</Subscript> grasses in situ in the eastern USA

Background and aims

Elemental uptake in serpentine floras in eastern North America is largely unknown. The objective of this study was to determine major and trace element concentrations in soil and leaves of three native pseudo-metallophyte C₄ grasses in situ at five sites with three very different soil types, including three serpentine sites, in eastern USA.

Methods

Pseudo-total and extractible concentrations of 15 elements were measured and correlated from the soils and leaves of three species at the five sites.

Results

Element concentrations in soils of pseudo-metallophytes varied up to five orders of magnitude. Soils from metalliferous sites exhibited higher concentrations of their characteristic elements than non-metalliferous. In metallicolous populations, elemental concentrations depended on the element. Concentrations of major elements (Ca, Mg, K) in leaves were lower than typical toxicity thresholds, whereas concentrations of Zn were higher.

Conclusions

In grasses, species can maintain relatively low metal concentrations in their leaves even when soil concentrations are richer. However, in highly Zn-contaminated soil, we found evidence of a threshold concentration above which Zn uptake increases drastically. Finally, absence of main characteristics of serpentine soil at one site indicated the importance of soil survey and restoration to maintain serpentinophytes communities and avoid soil encroachment.