Excess copper induced proteomic changes in the marine brown algae Sargassum fusiforme

Simultaneous exposure to nanoplastics and cadmium mitigates microalgae cellular toxicity: Insights from molecular simulation and metabolomics

In the severe pollution area of nanoplastics (NPs) and cadmium ions (Cd2+), the joint effects of their high environmental concentrations on primary producers may differ from those of low environmental doses. Thus, we investigated the physiological changes, cell morphology, molecular dynamic simulation, phenotypic interactions, and metabolomics responses of C. pyrenoidosa to high environmental concentrations of NPs and Cd2+ after 12-d acclimation. After 12-d cultivation, mono-NPs and mono-Cd2+ reduced cell density and triggered antioxidant enzymes, extracellular polymeric substances (EPS) production, and cell aggregation to defend their unfavorable effects. Based on the molecular dynamic simulation, the chlorine atoms of the NPs and Cd2+ had charge attraction with the nitrogen and phosphorus atoms in the choline and phosphate groups in the cell membrane, thereby NPs and Cd2+ could adsorb on the cells to destroy them. In the joint exposure, NPs dominated the variations of ultrastructure and metabolomics and alleviated the toxicity of NPs and Cd2+. Due to its high environmental concentration, more NPs could compete with the microalgae for Cd2+ and thicken cell walls, diminishing the Cd2+ content and antioxidant enzymes of microalgae. NPs addition also decreased the EPS content, while the bound EPS with -CN bond was kept to detoxicate Cd2+. Metabolomics results showed that the NPs downregulated nucleotide, arachidonic acid, and tryptophan metabolisms, while the Cd2+ showed an opposite trend. Compared with their respective exposures, metabolomics results found the changes in metabolic molecules, suggesting the NPs_Cd2+ toxicity was mitigated by balancing nucleotide, arachidonic acid, tryptophan, and arginine and proline metabolisms. Consequently, this study provided new insights that simultaneous exposure to high environmental concentrations of NPs and Cd2+ mitigated microalgae cellular toxicity, which may change their fates and biogeochemical cycles in aquatic systems.

Quantitative proteomic analysis of the mechanism of Cd toxicity in Enterobacter sp. FM-1: Comparison of different growth stages

Enterobacter sp. are widely used in bioremediation, but the mechanism of Cadmium (Cd) toxicity in Enterobacter sp. has been poorly studied. In the present study, we determined the tolerance of Enterobacter sp. FM-1 to Cd by analyzing the physiological and biochemical responses of FM-1 induced under Cd stress. Differentially expressed proteins (DEPs) under exposure to different Cd environments were analyzed by 4D-label-free proteomics to provide a comprehensive understanding of Cd toxicity in FM-1. The greatest total number of DEPs, 1148, was found in the High concentration vs. Control comparison group at 10 h. When protein expression was compared after different incubation times, FM-1 showed the highest Cd tolerance at 48 h. Additionally, with an increasing incubation time, different comparison groups gradually began to show similar growth patterns, which was reflected in the GO enrichment analysis. Notably, only 815 proteins were identified in the High concentration vs. Control group, and KEGG enrichment analysis revealed that these proteins were significantly enriched in the pyruvate metabolism, oxidative phosphorylation, peroxisome, glyoxylate and dicarboxylate metabolism, and citrate cycle pathways. These results suggested that an increased incubation time allows FM-1 adapt and survive in an environment with Cd toxicity, and protein expression significantly increased in response to oxidative stress in a Cd-contaminated environment during the pre-growth period. This study provides new perspectives on bacterial participation in bioremediation and expands our understanding of the mechanism of bacterial resistance under Cd exposure.

Bivalent copper ions presence triggers removal and homeostatic mechanisms in the metal-resistant microorganism Apiotrichum loubieri M12

Microorganisms, especially those habiting mining environments, are of great importance for the retention of toxic metals in the environment. This work aimed to isolate a copper removing-microorganism from sediments of an Acid Mine Drainage-affected environment and to study the cellular responses trigger by metal presence. Apiotrichum loubieri M12 was able to tolerate and remove Cu(II) from liquid culture media, reaching a 30-35% removal capacity when it was exposed to 40 μg mL^-1 Cu(II) after 48 h. Analysis of the biomass exposed to the metal through SEM-EDS showed copper presence on the cell surface and variations in the proportion of other biomass constituent elements. Proteomics revealed that the presence of Cu(II) induces differential expression of intracellular proteins involved in a wide variety of metabolic processes. Interestingly, a specific response to the metal was detected in cell-free supernatants, in which copper binding proteins were identified. A large number of proteins with metal ion binding sites were detected both at intra and extracellular levels. The microorganism responds not only by adjusting intracellular protein expression, but also by adjusting expression of proteins in the extracellular space.

Solubility of aerosol minor and trace elements in Xiamen Island, Southeast China: Size distribution, health risk and dry deposition

Aerosol element solubility is essential to evaluate the damage to the environment and human health. In this work, the size distribution of total and soluble elements in eight particle size ranges with diameter <0.25, 0.25-0.44, 0.44-1.0, 1.0-1.4, 1.4-2.5, 2.5-10, 10-16 and >16 μm was investigated in Xiamen Island, southeast China from March 2018 to June 2020. The results showed that both total and soluble elements exhibited significant size dependence without obvious seasonal variations, and their relative contributions to PM₁ mass were much lower than in particles larger than 1 μm. The correlations between some elements in soluble fraction were quite different from those in total fraction and the correlations also varied with particle size due to their different solubility. The solubility of Al, Fe, Ag and Cr was relatively low compared with other elements. Moreover, the solubility of Na, Mg, Ca, Mn and Ag was less dependent on particle size while Al, Fe and other trace elements exhibited the highest solubility in PM₁ and the lowest in PM_>10. Overall, the solubility of elements is primarily a function of aerosol origin and size. The carcinogenic risks of metal exposure via inhalation for children (3.31 × 10^-6) and adults (4.42 × 10^-6) were slightly higher than the guideline of cancer risk with >60 % from V. As for non-carcinogenic risk, the hazard index values for children and adults were 1.59 and 0.53, respectively, with Mn, V and Ni together accounting for >85 % of the risk. >85 % of the size-dependent dry deposition fluxes of the selected soluble elements over the Xiamen Bay were contributed by particles larger than 10 μm due to their high deposition velocities. The atmospheric inputs of bioavailable Fe and Cu to the sea exceeded the required amounts relative to inorganic nitrogen to meet the growth of phytoplankton.

Physiological and proteomic responses of Chlamydomonas reinhardtii to arsenate and lead mixtures

Arsenic (As) and lead (Pb) are frequently emitted from various sources into environment, but microbial responses to their combined toxicity have not been systematically investigated. In this study, Chlamydomonas reinhardtii was exposed to two levels of arsenate (As (V), 50, 500 μg/L), Pb (II) (500, 5000 μg/L) and their mixture (50 μg/L As (V) + 500 μg/L Pb (II); 500 μg/L As (V) + 5000 μg/L Pb (II)). The growth of C. reinhardtii was inhibited more remarkably by As (V) than by Pb (II). The As stress was alleviated by Pb in the 50 μg/L As (V) + 500 μg/L Pb (II) treatment, but was enhanced upon the 500 μg/L As (V) + 5000 μg/L Pb (II) exposure, with more pronounced changes in a number of physiological parameters of the algal cells. Proteomic results showed that 71 differently expressed proteins (DEPs) in the treatment of 50 μg/L As (V) + 500 μg/L Pb (II), and 167 DEPs were identified in that of 500 μg/L As (V) + 5000 μg/L Pb (II). These proteins were involved in energy metabolism, photosynthetic carbon fixation, reactive oxygen scavenging and defense, and amino acid synthesis. Taken together, these physiological and proteomic data demonstrated that C. reinhardtii could resist the As (V) and Pb (II) combined treatments through extracellular complexation and intracellular pathways.

Metal stresses modify soluble proteomes and toxin profiles in two Mediterranean strains of the distributed dinoflagellate Alexandrium pacificum

HABs involving Alexandrium pacificum have been reported in metal-contaminated ecosystems, suggesting that this distributed species adapts to and/or can tolerate the effects of metals. Modifications in soluble proteomes and PST contents were characterized in two Mediterranean A. pacificum strains exposed to mono- or polymetallic stresses (zinc, lead, copper, cadmium). These strains were isolated from two anthropized locations: Santa Giusta Lagoon (Italy, SG C10-3) and the Tarragona seaport (Spain, TAR C5-4F). In both strains, metals primarily downregulated key photosynthesis proteins. Metals also upregulated other proteins involved in photosynthesis (PCP in both strains), the oxidative stress response (HSP 60, proteasome and SOD in SG C10-3; HSP 70 in TAR C5-4F), energy metabolism (AdK in TAR C5-4F), neoglucogenesis/glycolysis (GAPDH and PEP synthase in SG C10-3) and protein modification (PP in TAR C5-4F). These proteins, possibly involved in adaptive proteomic responses, may explain the development of these A. pacificum strains in metal-contaminated ecosystems. The two strains showed different proteomic responses to metals, with SG C10-3 upregulating more proteins, particularly PCP. Among the PSTs, regardless of the metal and the strain studied, C2 and GTX4 predominated, followed by GTX5. Under the polymetallic cocktail, (i) total PSTs, C2 and GTX4 reached the highest levels in SG C10-3 only, and (ii) total PSTs, C2, GTX5 and neoSTX were higher in SG C10-3 than in TAR C5-4F, whereas in SG C10-3 under copper stress, total PSTs, GTX5, GTX1 and C1 were higher than in the controls, revealing variability in PST biosynthesis between the two strains. Total PSTs, C2, GTX4 and GTX1 showed significant positive correlations with PCP, indicating that PST production may be positively related to photosynthesis. Our results showed that the A. pacificum strains adapt their proteomic and physiological responses to metals, which may contribute to their ecological success in highly anthropized areas.

First assessment of Atlantic open ocean Sargassum spp. metal and metalloid concentrations

Over the last decade, increasing proliferations of Atlantic Sargassum populations have led to massive beaching with disastrous environmental consequences. This study is a preliminary assessment of open ocean Sargassum spp. element concentration to assess their potential contribution on coastal ecosystems. Sargassum spp. samples from seven sites, collected along a transect from the center of the Atlantic Ocean to near the coast of Martinique (French West Indies), were analyzed to determine their potential metal and metalloid enrichment. Mean element concentrations from the Sargassum spp. samples were ranked in the following descending order: As > Fe > Mn > Al > Zn > V > Ni > Cu > Cr > Cd > Hg. Element concentrations are relatively low compared to previous results of beached Sargassum spp. except for As that need to be carefully considered before reusing Sargassum spp.

Bioremediation of micropollutants using living and non-living algae - Current perspectives and challenges

The emergence and continual accumulation of industrial micropollutants such as dyes, heavy metals, organic matters, and pharmaceutical active compounds (PhACs) in the ecosystem pose an alarming hazard to human health and the general wellbeing of global flora and fauna. To offer eco-friendly solutions, living and non-living algae have lately been identified and broadly practiced as promising agents in the bioremediation of micropollutants. The approach is promoted by recent findings seeing better removal performance, higher efficiency, surface area, and binding affinity of algae in various remediation events compared to bacteria and fungi. To give a proper and significant insight into this technology, this paper comprehensively reviews its current applications, removal mechanisms, comparative efficacies, as well as future outlooks and recommendations. In conducting the review, the secondary data of micropollutants removal have been gathered from numerous sources, from which their removal performances are analyzed and presented in terms of strengths, weaknesses, opportunities, and threats (SWOT), to specifically examine their suitability for selected micropollutants remediation. Based on kinetic, isotherm, thermodynamic, and SWOT analysis, non-living algae are generally more suitable for dyes and heavy metals removal, meanwhile living algae are appropriate for removal of organic matters and PhACs. Moreover, parametric effects on micropollutants removal are evaluated, highlighting that pH is critical for biodegradation activity. For selective pollutants, living and non-living algae show recommendable prospects as agents for the efficient cleaning of industrial wastewaters while awaiting further supporting discoveries in encouraging technology assurance and extensive applications.

Transcriptomic sequencing reveals the response of Dunaliella salina to copper stress via the increased photosynthesis and carbon mechanism

Copper (Cu) is one of the essential microelements for plants and algae. It can stimulate growth and photosynthesis at low concentration but inhibit them at higher concentration. The knowledge of molecular response mechanisms to copper stress in green algae is still limited. The responses of the green algae Dunaliella salina to Cu stress were studied using the physiochemical indexes and RNA-seq analysis. The physiochemical indexes such as growth rate, the content of chlorophyll and soluble sugar, photosynthesis and peroxidase activity were all changed in D. salina under Cu stress. In addition, a total of 3799 differentially expressed genes (DEGs) were identified between the control and Cu-treated group. Among these, 2350 unigenes were up-regulated whereas 1449 were down-regulated. Here, the DEGs encoding proteins relevant to photosynthesis, carbon assimilation and carbohydrate mechanism were significantly up-regulated in the Cu-treated group. In addition, the unigenes encoding proteins involved in the antioxidant system and heat shock proteins were also up-regulated, and these were consistent with the expression patterns based on TPM (transcripts per million) values. This study shows that the enhanced growth and photosynthesis and carbon mechanism in D. salina can be triggered by copper, which will lay a firm foundation for future breeding and carotenoid production, further highlighting the underlying application of D. salina as a functional food.

Characterization of copper stress response in Fusarium tricinctum M6: A metal-resistant microorganism isolated from an acid mine drainage-affected environment

Acid mine drainage-affected environments are interesting microbial niches for the isolation of metal-resistant microorganisms. In this sense, the aim of the present work is to isolate and characterize metal-resistant microorganisms from sediments of an abandoned gold mine located in San Luis (Argentina). For these purposes, the metal removal capacity and the microelemental composition of the biomass exposed to metals were evaluated. Likewise, proteomic techniques were applied to understand the removal and resistance mechanisms. Fusarium tricinctum M6 was isolated and identified as tolerant to Cu(II), Fe(II) and Cr(VI). When faced with 40 µg mL-1 Cu(II), the growth was affected by 60% and the removal capacity was 30-35%. Copper was found uniformly distributed in the biomass (5.23% w/w) and variations in the proportion of other biomass constituent elements were detected. When exposed to Cu(II), F. tricinctum M6 showed differential expression of intra and extracellular proteins involved in different metabolic processes. A large number of proteins with metal ion binding sites were detected both at intra and extracellular levels. The results obtained in the present work indicated bioadsorption of the metal on the cell surface and an important readjustment of the protein expression to counteract the stress produced by Cu(II).

Metallothionein production is a common tolerance mechanism in four species growing in polluted Cu mining areas in Peru

Cu pollution is a problem in mining areas in Peru. Here we evaluate the phytoextraction capacity, physiological and proteomic responses of four species growing in copper-contaminated areas in Arequipa, Peru. The plants used in the experiments were obtained by collecting seedlings (Tessaria integrifolia, Bacharis salicifolia), rhizomes (Eleocharis montevidensis) and seeds (Chenopodium murale) along a polluted river. They were exposed to solutions containing 2, 4, 8, 16 and 32 mg Cu L^-1 during 20 days. Growth was affected in a concentration-dependent way. According to the tolerance index, B. salicifolia and C. murale were the most sensitive species, but with greater Cu phytoextraction capacity and accumulation in the biomass. The content and ratio of photosynthetic pigments changed differently for each specie and carotenoids level were less affected than chlorophyll. Cu also induced changes in the protein and sugar contents. Antioxidant enzyme activities (catalase and superoxide dismutase) increased with a decrease in the malondialdehyde. There were marked changes in the protein 2D-PAGE profiles with an increase in the abundance of metallothioneins (MT) of class II type I and II. Our results suggest that these species can grow in Cu polluted areas because they developed multiple tolerance mechanisms, such as and MTs production seems a important one.

Omics approaches for microalgal applications: Prospects and challenges

In recent impetus of phycological research, microalgae have emerged as a potential candidate for various arena of application-driven research. Omics-based tactics are used for disentangling the regulation and network integration for biosynthesis/degradation of metabolic precursors, intermediates, end products, and identifying the networks that regulate the metabolic flux. Multi-omics coupled with data analytics have facilitated understanding of biological processes and allow ample access to diverse metabolic pathways utilized for genetic manipulations making microalgal factories more efficient. The present review discusses state-of-art "Algomics" and the prospect of microalgae and their role in symbiotic association by using omics approaches including genomics, transcriptomics, proteomics and metabolomics. Microalgal based uni- and multi-omics approaches are critically analyzed in wastewater treatment, metal toxicity and remediation, biofuel production, and therapeutics to provide an imminent outlook for an array of environmentally sustainable and economically viable microalgal applications.

Impacts of Aerosol Copper on Marine Phytoplankton: A Review

Atmospheric deposition brings both nutrients and toxic components to the surface ocean, resulting in important impacts on phytoplankton. Field and lab studies have been done on the iron (Fe) fertilization on marine phytoplankton. However, studies on other trace metals are limited. Both bioassay experiments and field observations have suggested that aerosols with high copper (Cu) concentrations can negatively affect the primary productivity and change phytoplankton community structure. Note that with increasing human activities and global environmental changes (e.g., ocean acidification, warming, deoxygenation, etc.), the input of aerosol Cu could exceed toxicity thresholds at certain times or in some sensitive oceanic regions. Here, we provide a comprehensive review on aerosol Cu and marine phytoplankton studies by summarizing (1) physiological effects and toxicity thresholds of Cu to various phytoplankton taxa, (2) interactions between Cu and other metals and major nutrients, and (3) global distribution of surface seawater Cu and atmospheric Cu. We suggest that studies on aerosols, seawater chemistry, and phytoplankton should be integrated for understanding the impacts of aerosol Cu on marine phytoplankton, and thereafter the air–sea interaction via biogeochemical processes.

Insights into the Regulation of Algal Proteins and Bioactive Peptides Using Proteomic and Transcriptomic Approaches

Oceans abound in resources of various kinds for R&D and for commercial applications. Monitoring and bioprospecting allow the identification of an increasing number of key natural resources. Macroalgae are essential elements of marine ecosystems as well as a natural resource influenced by dynamic environmental factors. They are not only nutritionally attractive but have also demonstrated potential health benefits such as antioxidant, antihypertensive, and anti-inflammatory activities. Several bioactive peptides have been observed following enzymatic hydrolysis of macroalgal proteins. In addition, significant differences in protein bioactivities and peptide extracts of wild and cultivated macroalgae have been highlighted, but the metabolic pathways giving rise to these bioactive molecules remain largely elusive. Surprisingly, the biochemistry that underlies the environmental stress tolerance of macroalgae has not been well investigated and remains poorly understood. Proteomic and functional genomic approaches based on identifying precursor proteins and bioactive peptides of macroalgae through integrated multi-omics analysis can give insights into their regulation as influenced by abiotic factors. These strategies allow evaluating the proteomics profile of regulation of macroalgae in response to different growth conditions as well as establishing a comparative transcriptome profiling targeting structural protein-coding genes. Elucidation of biochemical pathways in macroalgae could provide an innovative means of enhancing the protein quality of edible macroalgae. This could be ultimately viewed as a powerful way to drive the development of a tailored production and extraction of high value molecules. This review provides an overview of algal proteins and bioactive peptide characterization using proteomics and transcriptomic analyses.

Effects of Copper and pH on the Growth and Physiology of Desmodesmus sp. AARLG074

Copper (Cu) is a heavy metal that is widely used in industry and as such wastewater from mining or industrial operations can contain high levels of Cu. Some aquatic algal species can tolerate and bioaccumulate Cu and so could play a key role in bioremediating and recovering Cu from polluted waterways. One such species is the green alga Desmodesmus sp. AARLG074. The aim of this study was to determine how Desmodesmus is able to tolerate large alterations in its external Cu and pH environment. Specifically, we set out to measure the variations in the Cu removal efficiency, growth, ultrastructure, and cellular metabolite content in the algal cells that are associated with Cu exposure and acidity. The results showed that Desmodesmus could remove up to 80% of the copper presented in Jaworski’s medium after 30 min exposure. There was a decrease in the ability of Cu removal at pH 4 compared to pH 6 indicating both pH and Cu concentration affected the efficiency of Cu removal. Furthermore, Cu had an adverse effect on algal growth and caused ultrastructural changes. Metabolite fingerprinting (FT-IR and GC-MS) revealed that the polysaccharide and amino acid content were the main metabolites affected under acid and Cu exposure. Fructose, lactose and sorbose contents significantly decreased under both acidic and Cu conditions, whilst glycerol and melezitose contents significantly increased at pH 4. The pathway analysis showed that pH had the highest impact score on alanine, aspartate and glutamate metabolism whereas Cu had the highest impact on arginine and proline metabolism. Notably both Cu and pH had impact on glutathione and galactose metabolism.

Copper stress response in yeast Rhodotorula mucilaginosa AN5 isolated from sea ice, Antarctic

Heavy metal pollution in Antarctic is serious by anthropogenic emissions and atmospheric transport. To dissect the heavy metal adaptation mechanisms of sea-ice organisms, a basidiomycetous yeast strain AN5 was isolated and its cellular changes were analyzed. Morphological, physiological, and biochemical characterization indicated that this yeast strain belonged to Rhodotorula mucilaginosa AN5. Heavy metal resistance pattern of Cd > Pb = Mn > Cu > Cr > Hg was observed. Scanning electron microscopic (SEM) results exhibited altered cell surface morphology under the influence of copper metal compared to that with control. The determination of physiological and biochemical changes manifested that progressive copper treatment significantly increased antioxidative reagents content and enzymes activity in the red yeast, which quench the active oxygen species to maintain the intercellular balance of redox state and ensure the cellular fission and growth. Comparative proteomic analysis revealed that, under 2 mM copper stress, 95 protein spots were tested reproducible changes of at least 10-fold in cells. Among 95 protein spots, 43 were elevated and 52 were decreased synthesis. After MALDI TOF MS/MS analysis, 51 differentially expressed proteins were identified successfully and classified into six functional groups, including carbohydrate and energy metabolism, nucleotide and protein metabolism, protein folding, antioxidant system, signaling, and unknown function proteins. Function analysis indicated that carbohydrate and energy metabolism-, nucleotide and protein metabolism-, and protein folding-related proteins played central role to the heavy metal resistance of Antarctic yeast. Generally, the results revealed that the yeast has a great capability to cope with heavy metal stress and activate the physiological and protein mechanisms, which allow more efficient recovery after copper stress. Our studies increase understanding of the molecular resistance mechanism of polar yeast to heavy metal, which will be benefitted for the sea-ice isolates to be a potential candidate for bioremediation of metal-contaminated environments.

Characterization of additional zinc ions on the growth, biochemical composition and photosynthetic performance from Spirulina platensis

In this study, the effect of various initial Zn²⁺ concentration additionally on microalgae growth and biochemical composition were investigated. The Spirulina platensis biomass of each concentration reached the maximum at the end of the cultivation. However, high levels could severely inhibit the growth of microalgae. Fluorescence activity occurred changes in response to heavy metal stress. Moreover, biochemical composition in Spirulina platensis altered under zinc stress, and the highest contents of phycocyanin (PC), Chlorophyll-a (Chl-a), Carotenoid and zinc accumulation were obtained. The proportion of saturated and polyunsaturated fatty acids increased constantly in response to Zn²⁺ exposure. Overall, this study indicated that the use of Spirulina platensis is a viable method for treating zinc containing wastewater and harvested microalgae can be processed into high-zinc products.

Potential of Trichoderma koningii to eliminate alachlor in the presence of copper ions

The filamentous fungus Trichoderma koningii is capable of fast and effective eliminate alachlor (90% after 72 h when added separately and 80-60% in the presence of 1-5 mM of copper). After 168 h over 99% elimination of alachlor resulted in detoxification and was connected with the mitigation of reactive oxygen species (ROS) production. Using MS/MS techniques, seven dechlorinated and hydroxylated metabolites were identified. Cytochrome P450 and laccase participate in biotransformation of the herbicide by this non-ligninolytic fungus. Laccase activity is stimulated both by copper and the mixture of copper and alachlor, which seems to be important for combined pollutants. T. koningii is characterized by high tolerance to copper (up to 7.5 mM). The metal content in mycelia reached 0.9-7.76 mg in 1 g of dry biomass. Our results suggest that T. koningii strain seems to be a promising tool for bioremediation of agricultural areas co-contaminated with copper-based fungicides and chloroacetanilide herbicides.

Proteome characterization of copper stress responses in the roots of sorghum

Copper (Cu) is a important micronutrient for plants, but it is extremely toxic to plants at high concentration and can inactivate and disturb protein structures. To explore the Cu stress-induced tolerance mechanism, the present study was conducted on the roots of sorghum seedlings exposed to 50 and 100 µM CuSO₄ for 5 days. Accumulation of Cu increased in roots when the seedlings were treated with the highest concentration of Cu²⁺ ions (100 μM). Elevated Cu concentration provoked notable reduction of Fe, Zn, Ca, and Mn uptake in the roots of sorghum seedlings. In the proteome analysis, high-throughput two-dimensional polyacrylamide gel electrophoresis combined with MALDI-TOF-TOF MS was performed to explore the molecular responses of Cu-induced sorghum seedling roots. In two-dimensional silver-stained gels, 422 protein spots were identified in the 2-D gel whereas twenty-one protein spots (≥1.5-fold) were used to analyze mass spectrometry from Cu-induced sorghum roots. Among the 21 differentially expressed proteins, 10 proteins were increased, while 11 proteins were decreased due to the intake of Cu ions by roots of sorghum. Abundance of most of the identified proteins from the roots that function in stress response and metabolism was remarkably enhanced, while proteins involved in transcription and regulation were severely reduced. Taken together, these results imply insights into a potential molecular mechanism towards Cu stress in C₄ plant, sorghum.

Early transcriptional response pathways in Daphnia magna are coordinated in networks of crustacean-specific genes

Natural habitats are exposed to an increasing number of environmental stressors that cause important ecological consequences. However, the multifarious nature of environmental change, the strength and the relative timing of each stressor largely limit our understanding of biological responses to environmental change. In particular, early response to unpredictable environmental change, critical to survival and fitness in later life stages, is largely uncharacterized. Here, we characterize the early transcriptional response of the keystone species Daphnia magna to twelve environmental perturbations, including biotic and abiotic stressors. We first perform a differential expression analysis aimed at identifying differential regulation of individual genes in response to stress. This preliminary analysis revealed that a few individual genes were responsive to environmental perturbations and they were modulated in a stressor and genotype-specific manner. Given the limited number of differentially regulated genes, we were unable to identify pathways involved in stress response. Hence, to gain a better understanding of the genetic and functional foundation of tolerance to multiple environmental stressors, we leveraged the correlative nature of networks and performed a weighted gene co-expression network analysis. We discovered that approximately one-third of the Daphnia genes, enriched for metabolism, cell signalling and general stress response, drives transcriptional early response to environmental stress and it is shared among genetic backgrounds. This initial response is followed by a genotype- and/or condition-specific transcriptional response with a strong genotype-by-environment interaction. Intriguingly, genotype- and condition-specific transcriptional response is found in genes not conserved beyond crustaceans, suggesting niche-specific adaptation.

Modifications of the soluble proteome of a mediterranean strain of the invasive neurotoxic dinoflagellate Alexandrium catenella under metal stress conditions

The soluble proteome of the mediterranean strain ACT03 of the invasive neurotoxic dinoflagellate Alexandrium catenella exposed to lead or zinc at 6, 12 or 18μM (total concentrations), or under control conditions, was characterized by two-dimensional gel electrophoresis (2-DE). Zinc reduced (P<0.05) the total number of protein spots (-41%, -52% and -60%, at 6, 12 or 18μM, respectively). Besides, most of the proteins constituting the soluble proteome were down-regulated in response to lead or zinc stresses. These proteins were involved mainly in photosynthesis (20-37% for lead; 36-50% for zinc) (ribulose-1,5-bisphosphate carboxylase/oxygenase: RUBISCO; ferredoxin-NADP⁺ reductase: FNR; peridinin-chlorophyll a-protein: PCP), and in the oxidative stress response (29-34% for lead; 17-36% for zinc) (superoxide dismutase: SOD; proteasome α/β subunits). These negative effects could be partly compensated by the up-regulation of specific proteins such as ATP-synthase β subunit (+16.3 fold after exposure to lead at 12μM). Indeed, an increase in the abundance of ATP-synthase could enrich the ATP pool and provide more energy available for the cells to survive under metal stress, and make the ATP-synthase transport of metal cations out of the cells more efficient. Finally, this study shows that exposure to lead or zinc have a harmful effect on the soluble proteome of A. catenella ACT03, but also suggests the existence of an adaptative proteomic response to metal stresses, which could contribute to maintaining the development of this dinoflagellate in trace metal-contaminated ecosystems.

Enhancing anti-microbial properties of wood-plastic composites produced from timber and plastic wastes

Considering the resource waste and environmental burden for timber and plastic materials ending up at landfills, this study proposed upcycling wood and plastic waste into value-added wood-plastic composites (WPCs), complying with the standard requirements of flexural strength, thickness swelling, water absorption and thermal insulation. Biological deterioration is a major concern of WPCs. Bacterial survival, fungal attack and algal growth of bactericide-treated WPCs were holistically analysed. Melamine resin was adopted for impregnating anti-microbial agents on the surface. All the agents showed excellent bactericidal rate (Escherichia coli), yet poly-diallyl-dimethyl-ammonium chloride (PolyDADMAC) and silver had the lowest minimum inhibitory concentrations. In terms of weight loss and strength reduction due to fungal decay (Coriolus versicolor), PolyDADMAC, silver and cetyltrimethylammonium bromide (CTAB) imparted the highest resistance on the WPCs. Moreover, PolyDADMAC and copper provided the most protection against algal growth (Chlorella vulgaris), and the former presented durable inhibitory effect. This study presents a value-added solution to wood/plastic waste recycling.

Photosynthetic activity and proteomic analysis highlights the utilization of atmospheric CO2 by Ulva prolifera (Chlorophyta) for rapid growth

Free-floating Ulva prolifera is one of the causative species of green tides. When green tides occur, massive mats of floating U. prolifera thalli accumulate rapidly in surface waters with daily growth rates as high as 56%. The upper thalli of the mats experience environmental changes such as the change in carbon source, high salinity, and desiccation. In this study, the photosynthetic performances of PSI and PSII in U. prolifera thalli exposed to different atmospheric carbon dioxide (CO₂ ) levels were measured. Changes in photosynthesis within salinity treatments and dehydration under different CO₂ concentrations were also analyzed. The results showed that PSII activity was enhanced as CO₂ increased, suggesting that CO₂ assimilation was enhanced and U. prolifera thalli can utilize CO₂ in the atmosphere directly, even when under moderate stress. In addition, changes in the proteome of U. prolifera in response to salt stress were investigated. Stress-tolerance proteins appeared to have an important role in the response to salinity stress, whereas the abundance of proteins related to metabolism showed no significant change under low salinity treatments. These findings may be one of the main reasons for the extremely high growth rate of free-floating U. prolifera when green tides occur.

Genome-wide analysis of transcription and photosynthesis inhibition in the harmful dinoflagellate Prorocentrum minimum in response to the biocide copper sulfate

Copper is an essential trace metal for organisms; however, excess copper may damage cellular processes. Their efficiency and physiological effects of biocides have been well documented; however, molecular transcriptome responses to biocides are insufficiently studied. In the present study, a 6.0K oligonucleotide chip was developed to investigate the molecular responses of the harmful dinoflagellate Prorocentrum minimum to copper sulfate (CuSO₄) treatment. The results revealed that 515 genes (approximately 8.6%) responded to CuSO₄, defined as being within a 2-fold change. Further, KEGG pathway analysis showed that differentially expressed genes (DEGs) were involved in ribosomal function, RNA transport, carbon metabolism, biosynthesis of amino acids, photosystem maintenance, and other cellular processes. Among the DEGs, 49 genes were related to chloroplasts and mitochondria. Furthermore, the genes involved in the RAS signaling pathway, MAPK signaling pathway, and transport pathways were identified. An additional experiment showed that the photosynthesis efficiency decreased considerably, and reactive oxygen species (ROS) production increased in P. minimum after CuSO₄ exposure. These results suggest that CuSO₄ caused cellular oxidative stress in P. minimum, affecting the ribosome and mitochondria, and severely damaged the photosystem. These effects may potentially lead to cell death, although the dinoflagellate has developed a complex signal transduction process to combat copper toxicity.

Copper excess promotes propagation and induces proteomic change in root cultures of Hyoscyamus albus L

Hyoscyamus albus L. seedlings respond positively to copper (Cu) excess. In the present study, to understand how roots cope with Cu excess, propagation and proteome composition in the presence of Cu were examined using a root culture system. When H. albus roots were cultured in a medium without Cu, root growth deteriorated. However, in the presence of Cu, root growth increased in a concentration-dependent manner, and vigorous lateral root development was observed at 200 μM Cu. Cu accumulation in the roots increased with the Cu supply. Subcellular fractionation revealed that the highest amount of Cu was present in the cell wall-containing fraction, followed by the soluble fraction. However, the highest specific incorporation of Cu, in terms of fresh weight, was in the mitochondria-rich fraction. High Cu levels enhanced respiration activity. Comparative proteomic analysis revealed that proteins involved in carbohydrate metabolism, de novo protein synthesis, cell division, and ATP synthesis increased in abundance, whereas the proteasome decreased. These results indicate that Cu promotes propagation of H. albus roots through the activation of the energy supply and anabolism. Newly propagated root tissues and newly generated proteins that bind to Cu may provide space and reservoirs for deposition of additional Cu.

Leaf proteome characterization in the context of physiological and morphological changes in response to copper stress in sorghum

Copper (Cu) is an essential micronutrient required for normal growth and development of plants; however, at elevated concentrations in soil, copper is also generally considered to be one of the most toxic metals to plant cells due to its inhibitory effects against many physiological and biochemical processes. In spite of its potential physiological and economical significance, molecular mechanisms under Cu stress has so far been grossly overlooked in sorghum. To explore the molecular alterations that occur in response to copper stress, the present study was performed in ten-day-old Cu-exposed leaves of sorghum seedlings. The growth characteristics were markedly inhibited, and ionic alterations were prominently observed in the leaves when the seedlings were exposed to different concentrations (0, 100, and 150 µM) of CuSO4. Using two-dimensional gels with silver staining, 643 differentially expressed protein spots (≥1.5-fold) were identified as either significantly increased or reduced in abundance. Of these spots, a total of 24 protein spots (≥1.5-fold) from Cu-exposed sorghum leaves were successfully analyzed by MALDI-TOF-TOF mass spectrometry. Of the 24 differentially expressed proteins from Cu-exposed sorghum leaves, 13 proteins were up-regulated, and 11 proteins were down-regulated. The abundance of most identified protein species, which function in carbohydrate metabolism, stress defense and protein translation, was significantly enhanced, while that of another protein species involved in energy metabolism, photosynthesis and growth and development were severely reduced. The resulting differences in protein expression patterns together with related morpho-physiological processes suggested that these results could help to elucidate plant adaptation to Cu stress and provide insights into the molecular mechanisms of Cu responses in C4 plants.

Morpho-Physiological and Proteome Level Responses to Cadmium Stress in Sorghum

Cadmium (Cd) stress may cause serious morphological and physiological abnormalities in addition to altering the proteome in plants. The present study was performed to explore Cd-induced morpho-physiological alterations and their potential associated mechanisms in Sorghum bicolor leaves at the protein level. Ten-day-old sorghum seedlings were exposed to different concentrations (0, 100, and 150 μM) of CdCl2, and different morpho-physiological responses were recorded. The effects of Cd exposure on protein expression patterns in S. bicolor were investigated using two-dimensional gel electrophoresis (2-DE) in samples derived from the leaves of both control and Cd-treated seedlings. The observed morphological changes revealed that the plants treated with Cd displayed dramatically altered shoot lengths, fresh weights and relative water content. In addition, the concentration of Cd was markedly increased by treatment with Cd, and the amount of Cd taken up by the shoots was significantly and directly correlated with the applied concentration of Cd. Using the 2-DE method, a total of 33 differentially expressed protein spots were analyzed using MALDI-TOF/TOF MS. Of these, treatment with Cd resulted in significant increases in 15 proteins and decreases in 18 proteins. Major changes were absorbed in the levels of proteins known to be involved in carbohydrate metabolism, transcriptional regulation, translation and stress responses. Proteomic results revealed that Cd stress had an inhibitory effect on carbon fixation, ATP production and the regulation of protein synthesis. Our study provides insights into the integrated molecular mechanisms involved in responses to Cd and the effects of Cd on the growth and physiological characteristics of sorghum seedlings. We have aimed to provide a reference describing the mechanisms involved in heavy metal damage to plants.