Pyrene Stress Research Articles

Cohesive phycoremediation of pyrene by freshwater microalgae Selenastrum sp. and biodiesel production and its assessment.

In this study, the freshwater microalgae Selenastrum sp. was assessed for the effective degradation of pyrene and simultaneous production of biodiesel from pyrene-tolerant biomass. The growth of algae was determined based on the cell dry weight, cell density, chlorophyll content, and biomass productivity under different pyrene concentrations. Further, lipids from pyrene tolerant culture were converted into biodiesel by acid-catalyzed transesterification, which was characterized for the total fatty acid profile by gas chromatography. Increased pyrene concentration revealed less biomass yield and productivity after 20days of treatment, indicating potent pyrene biodegradation by Selenastrum sp. Biomass yield was unaffected till the 20mg/L pyrene. A 95% of pyrene bioremediation was observed at 20days of culturing. Lipid accumulation of 22.14%, as evident from the estimation of the total lipid content, indicated a marginal increase in corroborating pyrene stress in the culture. Fatty acid methyl esters yield of 63.06% (% per 100g lipids) was noticed from the pyrene tolerant culture. Moreover, fatty acid profile analysis of biodiesel produced under 10mg/L and 20mg/L pyrene conditionshowed escalated levels of desirable fatty acids in Selenastrum sp., compared to the control. Further, Selenastrum sp. and other freshwater microalgae are catalogued for sustainable development goals attainment by 2030, as per the UNSDG (United Nations Sustainable Development Goals) agenda. Critical applications for the Selenastrum sp. in bioremediation of pyrene, along with biodiesel production, are enumerated for sustainableand renewable energy production and resource management.

Transcriptomic and biochemical analysis of metabolic remodeling in Bacillus subtilis MSC4 under Benzo[a]pyrene stress

Polyaromatic benzo[a]pyrene (B[a]P) is a toxic carcinogenic environmental pollutant, and the use of microorganisms to remediate B[a]P contamination is considered to be one of the most effective strategies. However, there is still a gap in studying the metabolic remodeling of microorganisms under B[a]P stress. In this study, our systematically investigated the effects of B[a]P on the metabolism of Bacillus subtilis MSC4 based on transcriptomic, molecular and biochemical analyses. The results showed that in response to B[a]P stress, MSC4 formed more biofilm matrix and endospores, the structure of the endospores also was changed, which led to a reduction in their resistance and made them more difficult to germinate. In addition to an increase in glycolysis activity, the activities of tricarboxylic acid cycle, pentose phosphate pathway and the electron transport chain were decreased. B[a]P stress forced MSC4 to strengthen arginine synthesis, urea cycle, and urea decomposition, meanwhile, synthesize more ribonucleotides. The activity of DNA replication, transcription activities and the expression of multiple ribosomal protein genes were reduced. Moreover, all of the reported enzymes involved in B[a]P degradation showed decreased transcript abundance, and the degradation of B[a]P caused significant up-regulation of the gene expression of the acid inducible enzyme OxdC and the synthesis of acetoin. In addition, the cytotoxicity of B[a]P to bacteria was directly displayed in four aspects: increased intracellular level of reactive oxygen species (ROS), elevated cell membrane permeability, up-regulation of the cell envelope stress-sensing two-component system LiaRS, and downregulation of siderophores biosynthesis. Finally, B[a]P also caused morphological changes in the cells, with some cells exhibiting significant deformation and concavity. These findings provide effective research directions for targeted improvement the cellular activity of B[a]P-degrading strains, and is beneficial for further application of microorganisms to remediate B[a]P -contaminated soils.

Synergistic effect of pyrene and heavy metals (Zn, Pb, and Cd) on phytoremediation potential of Medicago sativa L.(alfalfa) in multi-contaminated soil.

The environment in India is contaminated with polycyclic aromatic hydrocarbons (PAHs) due to the occurrence of large anthropogenic activities, i.e., fuel combustion, mineral roasting, and biomass burning. Hence, 13 toxic PAHs were detected: phenanthrene, anthracene, fluoranthene, pyrene, and benz(a) anthracene, ben-zo; (b) fluoranthene, benzo(k) fluoranthene, benzo(a) pyrene, benzo(ghi)perylene, dibenz (ah) anthracene, indeno1,2,3-(cd) pyrene, coronene and coronene in the environment (i.e., ambient particulate matter, road dust, sludge, and sewage) of the most industrialized area. Pollutants such as heavy metals and polycyclic aromatic hydrocarbons co-contaminate the soil and pose a significant hazard to the ecosystem because these pollutants are harmful to both humans and the environment. Phytoremediation is an economical plant-based natural approach for soil clean-up that has no negative impact on ecosystems. The aim of this study was to investigate the effects of pyrene (500 mg kg-1), Zn (150 mg kg-1), Pb (150 mg kg-1), and Cd (150 mg kg-1) alone and in combination on the phytoextraction efficiency of Medicago sativa growing in contaminated soil. Plant biomass, biochemical activities, translocation factors, accumulation of heavy metals, and pyrene removal were determined. After 60 days of planting, compared with those of the control plants, the growth parameters, biomass, and chlorophyll content of the M. sativa plants were significantly lower, and the reactive oxygen species activity, such as proline and polyphenol content and metallothionein protein content, was markedly greater in the pyrene and heavy metal-polluted soils. Furthermore, the combined toxicity of pyrene and all three metals on M. sativa growth and biochemical parameters was significantly greater than that of pyrene, Zn, Pb, or Cd alone, indicating the synergistic effect of pyrene and heavy metals on cytotoxicity. Pyrene stress increased Cd accumulation in M. sativa. After pyrene exposure alone or in combination with Zn-pyrene, a greater pyrene removal rate (85.5-81.44%) was observed than that in Pb-pyrene, Cd-pyrene, and Zn-Pb-Cd-pyrene polluted soils (62.78-71.27%), indicating that zinc can enhance the removal of pyrene from contaminated soil. The resulting hypotheses demonstrated that Medicago sativa can be used as a promising phytoremediation agent for co-contaminated soil.

The Effects and Toxicity of Different Pyrene Concentrations on Escherichia coli Using Transcriptomic Analysis.

Pyrene is a pollutant in the environment and affects the health of living organisms. It is important to understand microbial-mediated pyrene resistance and the related molecular mechanisms due to its toxicity and biodegradability. Due to the unclear response mechanisms of bacteria to PAHs, this study detected the transcriptional changes in Escherichia coli under different pyrene concentrations using transcriptome sequencing technology. Global transcriptome analysis showed that the number of differentially expressed genes (DEGs) in multiple metabolic pathways increased with increasing concentrations of pyrene. In addition, the effects and toxicity of pyrene on Escherichia coli mainly included the up-regulation and inhibition of genes related to carbohydrate metabolism, membrane transport, sulfate reduction, various oxidoreductases, and multidrug efflux pumps. Moreover, we also constructed an association network between significantly differentially expressed sRNAs and key genes and determined the regulatory relationship and key genes of Escherichia coli under pyrene stress. Our study utilized pyrene as an exogenous stress substance to investigate the possible pathways of the bacterial stress response. In addition, this study provides a reference for other related research and serves as a foundation for future research.

Enhancing resistance and cell survival in Acipenser ruthenus liver, gill, and kidney cells: The potential of heat shock protein inducers against PAH-benzo[a]pyrene stress.

The Caspian Sea has faced many environmental challenges, such as oil pollution. Heat shock proteins (HSPs) play a critical role in stress conditions and physiological changes caused by disease or injury. By evaluating the effects of various HSP inducers (HSPi), including Pro-Tex® (NOP: 800 mM), amygdalin (AMG: 80 mM), and a novel synthetic compound derived from pirano piranazole (SZ: 80 µm) on isolated cells from Sterlet Sturgeon (Acipenser ruthenus) treated with 75% IC50 PAH-benzo[a]pyrene (BaP; B75). This study examines whether there is a correlation between exposure to the BaP pollutant and HSPs in fish. In vitro, after culturing cells from the liver, kidney, and gills, they were treated with HSPi compounds in the presence and absence of BaP. Western blotting was used to assess HSP27, HSP70, and HSP90 expression patterns. A variety of enzyme activities were measured before (without treatment) and after treatment with HSPis and HSPi + B75, including cytochrome P450 (CYP450) activity, specific enzyme activity for acetylcholinesterase (AChE), antioxidant capacity, liver indicator enzymes, cortisol levels, and immunity parameters. When compared to the control group, cells treated with B75 showed the lowest AChE enzyme activity (p < 0.0001). CYP450 activity was highest in group B75, while HSPi caused the opposite effect (p < 0.0001). HSPi + B75 increased HSP levels and antioxidant parameters while decreasing cortisol and liver indicator enzymes (p < 0.0001). HSPi may be a powerful and reliable method for enhancing the resistance of A. ruthenus to BaP stresses before exposure. Treating cells with HSP-inducing compounds, such as NOP, AMG, and SZ, can assist them in managing stress and increase HSP (27, 70, and 90) protein expression. Furthermore, the study findings suggest that HSPis can also mitigate the adverse effects of stress, ultimately increasing cell survival and resistance.

Study on reproductive endocrine disturbance and DNA damage mechanism of female Ruditapes philippinarum under Benzo[a]pyrene stress

The reproductive toxicity of polycyclic aromatic hydrocarbons (PAHs) in aquatic organisms has attracted increasing attention from scholars. Currently, research in this field primarily focuses on vertebrates such as zebrafish and other model species. However, there is still a significant knowledge gap in the toxicity of PAHs to invertebrates and its potential mechanisms. Benzo[a]pyrene (B[a]P) is one of the most representative PAHs. In this study, female Ruditapes philippinarum (R. philippinarum) was treated with B[a]P concentrations of 0, 0.8, 4, and 20 μg/L to investigate reproductive indicators in the proliferative, growth, mature, and spawn stages. Transcriptomics was used to investigate the expression of genes associated with the reproductive endocrine system, DNA repair, autophagy, apoptosis, and ovarian development at different reproductive stages. Our results suggested that B[a]P disrupted the endocrine system by interfering with the production of steroid hormones and the transmission of estrogen signals in female R. philippinarum. The structure of the ovarian DNA duplex is severely damaged under the stress of B[a]P, and a series of cellular responses caused by DNA damage are also interfered. Additionally, we observed a reduction in the gonadosomatic index (GSI) and mature oocytes numbers after B[a]P exposed. Tissue section indicated that severe damage to the ovarian structure at mature and spawn stages. In conclusion, this study combined transcriptomic and toxicological to explore the negative effects on ovarian development induced by B[a]P, focusing on reproductive endocrine disturbance and DNA damage.

Study of DNA methylation of hsd17β, er and reproductive endocrine disrupting effects in female Chlamys farreri under benzo[a]pyrene stress

Benzo[a]pyrene (B[a]P) is one kind of persistent organic pollutants (POPs) in the marine environment which has multiple toxic effects. However, epigenetic studies correlated with reproductive endocrine disruption in invertebrates have not been explored. In our study, Chlamys farreri in the mature stage were exposed to B[a]P (0, 0.4, 2 and 10 μg/L) for 5 and 10 d to explore the effects on reproductive endocrine and DNA methylation. The results proved that B[a]P stress significantly restrained the growth of mature oocytes, reduced the content of sex hormones, and affected the expression of genes related to ovarian development. Histological observation showed that the ovarian microstructure was damaged. The detection of SAM/SAH, dnmts, GNMT in the ovary showed that the level of global DNA methylation fluctuated. Significant hypermethylation of the hsd17β promoter region in the ovary was associated with a significant downregulation of its gene expression. In summary, our results suggested that exposure to B[a]P might affect DNA methylation to regulate key reproductive genes, interfere with the synthesis of sex hormones, and inhibit ovarian development. These findings provide a basis for a better understanding of how epigenetic mechanisms are involved in the response of marine invertebrates to POPs stress, opening up new avenues for incorporating environmental epigenetic approaches into marine invertebrate management and conservation plans.

Mangroves leaves phyllosphere bacteria community and its ability to survive under pyrene stress during the acclimation process

Plants in general and mangroves in particular can harbor hyper-diverse microorganisms in their different compartments including the phyllosphere area. This study used the leaves of three mangrove species; black mangrove (Avicenia germinans), red mangrove (Rhizophora mangle) and mangrove apple (Sonneratia alba) in order to evaluate the phyllosphere epiphytic bacterial community on their leaves surface and assess the ability of some epiphytic bacteria to tolerate and survive under pyrene stress. Through the 16S rRNA genes sequencing, 380203, 405203 and 344863 OTUs were identified respectively in the leaves of mangroves apple, black and red mangroves. The identified OTUs was positively correlated with leaves-wax (p < 0.05, r2 = 0.904), nitrogen (r2 = 0.72), phosphorus content (r2 = 0.62) and the water factor (r2 = 0.93). It was however highly and negatively correlated with the canopy cover (r2 = 0.93). The pyrene degradation rate in the mineral salt medium (MSM) containing pyrene as external stress was different in each mangrove species and varied depending on various factors. Therefore, through the succession culture in MSM, several bacteria strain belonging to Rhizobiales and Enterobacteres were found to be abundant in red mangroves. Bacteria belonging to Bacilliales and Sphingobacteriales were more abundant in mangroves apples and bacteria from Xanthomonadales and Sphingomonadales were more presents in back mangroves. The important finding was to reveal that the black mangrove at the non-submerged substrate, recorded the highest number of OTU, coinciding with its highest leaf's nitrogen and phosphorus content and most importantly, its highest rate of pyrene degradation. The general result of this study join previous research results and get place in the mangrove agenda, as part of a better understanding insight into the role of plant identity in driving the phyllosphere epiphytic microbial community structures in mangrove ecosystems.

Revealing the key species for pyrene degradation in Vallisneria natans rhizosphere sediment via triple chamber rhizome-box experiments

To identify key species associated with pyrene degradation in Vallisneria natans (V.natans) rhizosphere sediment, this work investigated the temporal and spatial changes in the rhizosphere microbial community and the relationship between the changes and the pyrene degradation process through a three-compartment rhizome-box experiment under pyrene stress. The degradation kinetics of pyrene showed that the order of degradation rate was rhizosphere > near-rhizosphere > non-rhizosphere. The difference in the pyrene degradation behavior in the sediments corresponded to the change in the proportions of dominant phyla (Firmicutes and Proteobacteria) and genera (g_Massilia f_Comamonadaceae, g_Sphingomonas). The symbiosis networks and hierarchical clustering analysis indicated that the more important phyla related to the pyrene degradation in the rhizosphere was Proteobacteria, while g_Sphigomonas, f_Comamonadaceae, and especially g_Massilia were the core genera. Among them, f_Comamonadaceae was the genus most affected by rhizosphere effects. These findings strengthened our understanding of the PAHs-degradation microorganisms in V.natans rhizosphere and are of great significance for enhancing phytoremediation on PAHs-contaminated sediment.

Nontargeted metabolomic analysis to unravel alleviation mechanisms of carbon nanotubes on inhibition of alfalfa growth under pyrene stress

Carbon nanotubes have displayed great potential in enhancing phytoremediation of PAHs polluted soils. However, the response of plants to the coexistence of carbon nanotubes and PAHs and the associated influencing mechanisms remain largely unknown. Here, the effect of carbon nanotubes on alfalfa growth and pyrene uptake under exposure to pyrene was evaluated through sand culture experiment and gas chromatography time-of-flight mass spectrometer (GC-TOF-MS) based metabolomics. Results showed that pyrene at 10 mg kg−1 obviously reduced the shoot fresh weight of alfalfa by 18.3 %. Multiwall carbon nanotubes (MWCNTs) at 25 and 50 mg kg−1 significantly enhanced the shoot fresh weight in a dose-dependent manner, nearly by 80 % at 50 mg kg−1. Pyrene was mainly accumulated in alfalfa roots, in which the concentration was 35 times as much as that in shoots. MWCNTs greatly enhanced the accumulation of pyrene in alfalfa roots, almost by two times at 50 mg kg−1, while decreased pyrene concentration in shoots, from 0.11 mg kg−1 to 0.044 mg kg−1 at MWCNTs concentration of 50 mg kg−1. Metabolomics data revealed that pyrene at 10 mg kg−1 trigged significant metabolic changes in alfalfa root exudates, downregulating 27 metabolites. MWCNTs generated an increase in the contents of some downregulated metabolites caused by pyrene stress, which were restored to the original level or even higher, mainly including organic acids and amino acids. MWNCTs significantly enriched some metabolic pathways positively correlated with shoot growth and pyrene accumulation in shoots under exposure to pyrene, including TCA cycle, glyoxylate and dicarboxylate metabolism, cysteine and methione metabolism as well as alanine, aspartate and glutamate metabolism. This work highlights the regulation effect of MWCNTs on the metabolism of root exudates, which are helpful for alfalfa to alleviate the stress from pyrene contamination.

Structural, metabolic, and functional characteristics of soil microbial communities in response to benzo[a]pyrene stress

Understanding the characteristics of soil microbes responding to benzo[a]pyrene (BaP) helps to deepen the knowledge of the risks of BaP to soil ecosystem. In this study, the structural, metabolic, and functional responses of soil microbial communities to BaP (8.11 mg kg−1) were investigated. Analysis of microbial community structure based on 16 S rRNA and ITS gene sequencing indicated that BaP addition enriched microbes associated with aromatic compound degradation (Sphingomonas, Bacilli, Fusarium) and oligotrophs (Blastocatellaceae, Rokubacteriales), but inhibited Cyanobacteria involved in nitrogen-fixing process. Network analysis showed that the bacterial community enhanced intraspecific cooperation, while fungal community mainly altered the keystone taxa under BaP stress. Biolog EcoPlate assay demonstrated that microbial metabolism of carbon sources, especially nitrogen-containing sources, was stimulated by BaP addition. Functional analysis based on enzyme activity tests, functional gene quantification, and function annotation showed that nitrogen-cycling processes, especially nitrogen fixation, were significantly inhibited. These results suggest that BaP-tolerant microbes may establish cooperative relationships and compete for resources and ecological niches with sensitive microbes, especially those associated with nitrogen cycling, ultimately leading to enhanced carbon source utilization and restricted nitrogen cycling. This study clearly elucidates the adaptation strategies and functional shifts of soil microbial communities to BaP contamination.

Bacterial Community in Mangrove Rhizosphere and Non-Rhizosphere and its Occurred Changes During the Acclimation Under Pyrene Stress

Although, bacterial abundance in rhizosphere and non-rhizosphere in terrestrial plants is thoroughly investigated, the trend in the mangrove ecosystem, which the environmental conditions are regularly changed is poorly documented. Furthermore, the bacterial acclimation under stress of heavy molecular weight organic pollutants process remains obscure about the taxonomic changes that may occur. In order to address these cited issues, this study was conducted in both rhizosphere and non-rhizosphere at different depths layer of the coastal mangrove of Yunxiao. Although the physicochemical properties in both rhizosphere and non-rhizosphere were unevenly distributed, no difference was observed about both rhizosphere and non-rhizosphere bacterial abundance. Moreover, the abundance at 5-10 cm of deep was significantly higher in both rhizosphere and non-rhizosphere. This could be attributed to the high available nutrients in the surface layer. The result of bacterial acclimation under pyrene stress revealed that pyrene significantly impacted the bacterial community composition and abundance. Nonetheless, a functional community of bacteria tolerant and surviving under pyrene stress was identified and the apparition of new phylopytes were favorable to the stability of the community as well as to the remediation of the polluted environment. The general results of this study elucidated that bacterial abundance in rhizosphere and non-rhizosphere of mangrove ecosystem could be different to that in terrestrial plants, and the domestication of functional bacteria could be an excellent asset for the adaptation of bacterial communities to environmental disturbances.

有机污染物芘胁迫下白菜生理特性变化规律

有机污染物芘胁迫下白菜生理特性变化规律

Benzo[a]pyrene might be transported by a TonB-dependent transporter in Novosphingobium pentaromativorans US6-1

Sphingomonads are well known for their ability to efficiently degrade polycyclic aromatic hydrocarbons (PAHs), but little is known about the mechanism of PAH uptake and transport across the cell membrane. RNA sequencing analysis of a sphingomonad, Novosphingobium pentaromativorans US6–1 showed that 38 TonB-dependent transporter (TBDT) genes were significantly upregulated under 5-ring PAH-benzo[a]pyrene (BaP) stress. In order to reveal whether TBDTs are involved in uptake and transport BaP in US6–1, the key TBDT genes were deleted to generate mutants. The results showed that the growth status of these mutants was not different from that of the wild-type strains, but the PAH degradation ability decreased, especially for the mutant strain Δtbdt-11, which did not encode the tbdt-11 gene. Meanwhile, the cell surface hydrophobicity (CSH) of Δtbdt-11 was found to be significantly lower than that of the wild-type strain under BaP stress. Furthermore, the transcriptional activity of genes encoding PAH degradative enzymes was found to be greatly reduced in Δtbdt-11. Confocal microscopy observations showed that US6–1 could transport BaP across the outer membrane, but this transport capacity was significantly reduced in Δtbdt-11 and wild-type US6–1 treated with PMF uncoupler, further confirming that the tbdt-11 gene was associated with PAH active transport.

Responsiveness change of biochemistry and micro-ecology in alkaline soil under PAHs contamination with or without heavy metal interaction

Co-presence of organic pollutants and heavy metals in soil is causing increasing concerns, but the lack of knowledge of relation between soil ecology and pollutant fate is limiting the developing of specific control strategy. This study investigated soil change under pyrene stress and its interaction with cadmium (Cd). Soil physicochemical properties were not seriously influenced. However, pollutants’ presence easily varied soil microbial activity, quantity, and diversity. Under high-level pyrene, Cd presence contributed to soil indigenous microorganisms’ adaption and soil microbial community structure stability. Soils with both pyrene and Cd presented 7.11–12.0% higher pyrene degradation compared with single pyrene treatment. High-throughput sequencing analysis indicated the proportion of Mycobacterium sp., a commonly known PAHs degrader, increased to 25.2–48.5% in treatments from 0.52% in control. This phenomenon was consistent with the increase of PAHs probable degraders (the ratio increased to 2.86–6.57% from 0.24% in control). Higher Cd bioavailability was also observed in soils with both pollutants than that with Cd alone. And Cd existence caused the elevation of Cd resistant bacterium Limnobacter sp. (increased to 12.2% in CdCK from 2.06% in control). Functional gene prediction also indicated that abundance of genes related to nutrient metabolism decreased dramatically with pollutants, while the abundances of energy metabolism, lipid metabolism, secondary metabolites biosynthesis-related genes increased (especially for aromatic compound degradation related genes). These results indicated the mutual effect and internal-interaction existed between pollutants and soils resulted in pollutants’ fate and soil microbial changes, providing further information regarding pollutants dissipation and transformation under soil microbial response.

Screening of pyrene degradation bacteria strain from the Kochia scoparia roots and its potential for promoting growth

The endophytic bacteria were isolated from the roots of polycyclic aromatic hydrocarbon (PAHs)-tolerant plant. We investigated their ability of PAHs degradation and plant growth promo-ting, with the aim to provide theoretical support for bacterial-plant cooperative soil remediation. Kochia scoparia living in coking plant area were selected for strains isolation. Eight endophytic bacteria strains, which used pyrene and 1-aminocyclopropane-1-carboxylic acid (ACC) as sole carbon and nitrogen source, were isolated from the roots of K. scoparia. Three endophytic bacteria, KSE4, KSE7 and KSE8, displayed high degradation efficiency in pyrene degradation experiment. They were identified as Bacillus sp., Pseudomonas sp., and Sphingobacterium sp., respectively. The abili-ties of those three strains to produce ACC deaminase and their effects on seed germination of K. scoparia were examined under pyrene stress through liquid culture tests. The results showed that the activity of ACC deaminase decreased with increasing pyrene concentration (0-15 mg·L-1). KSE7 had the strongest promotion effect. When pyrene concentration reached to 15 mg·L-1, the germination rate and bud length of K. scoparia increased by 44.8% and 61.1%, respectively. Our results indicated that KSE7 is a promising bacterial strain for soil remediation in coking plant area.

Comparative transcriptomic analysis provides insights into the response to the benzo(a)pyrene stress in aquatic firefly (Luciola leii)

Many studies have reported that behavior and bioluminescence of fireflies could be affected by changes in environment conditions. However, little is known about how the deterioration of the aquatic environment affects aquatic fireflies, particularly with respect to molecular responses following exposure to water pollutants, such as benzo(a)pyrene (BaP), which is a key indicator in environmental risk assessment because of the hazards it poses. Here, whole transcriptome sequencing and gene expression analysis were performed on freshwater fireflies (Luciola leii) exposed to BaP (concentration of 0.01 mg/L). Four transcriptomic libraries were constructed for the control and treatment groups, including two biological replicates. From the mixed pools (each pool contains 60 individuals from three time points), a total of 54,282 unigenes were assembled. Furthermore, 329,337 of Single-nucleotide Polymorphisms (SNPs) and 1324 of Simple Sequence Repeats (SSRs) were predicted using bioinformatics, which is useful for the future development of molecular markers. Subsequently, 2414 differently expressed genes (DEGs) were identified in response to BaP stress in comparison to the control, including 1350 up-regulated and 1064 down-regulated DEGs. Functional enrichment showed that these DEGs are primarily related to innate immunity; xenobiotic biodegradation and response, biomacromolecule metabolism, biosynthesis, and absorption. Eight key BaP-responsive DEGs were screened to survey the dynamic changes of expression in response to BaP stress at different time points, and to validate the RNA sequencing data using quantitative real-time PCR. The results indicate that the expression of genes encoding UGT, CYP3A, CYP9, CYP6AS5 and ADHP were induced, while those encoding UGT2B10L, PTGDS, and ALDH were reduced, to participate in response to the BaP exposure and potentially help counteract the adverse effects of BaP. This investigation provides insight into the toxicological response of fireflies to the occurrence of water deterioration.

Genome-wide transcriptional response of microRNAs to the benzo(a)pyrene stress in amphioxus Branchiostoma belcheri

Amphioxus, a cephalochordate found in sand habitats in shallow in-shore seawaters, has been widely used as a model in comparative immunology of chordates. However, the role of microRNAs (miRNAs) in amphioxus under abiotic stress, particularly xenobiotics with strong toxicity, remains largely unknown. Here, a widespread marine contaminant, benzo(a)pyrene (BaP) is used to evaluate its toxic effects on miRNA expression of amphioxus. Six small RNA libraries were sequenced from Branchiostoma belcheri. A total of 144 known and 157 novel miRNAs were identified using deep sequencing and bioinformatics approaches. A total of 58 differentially expressed miRNAs (DEMs) were screened, including 25 up- and 33 down-regulated DEMs under BaP stress. Target genes possibly regulated by DEMs were predicted, and their functional enrichment analyses were performed. Targets of DEMs are primarily involved in xenobiotic and cellular homeostasis, catabolic and transport process. They could be largely linked to nine immune- and toxin detoxification-related pathways, including metabolism of xenobiotics by cytochrome P450, drug metabolism-other enzymes, and drug metabolism-cytochrome P450, etc. Furthermore, quantitative real-time PCR (qRT-PCR) analysis for 12 key BaP-responsive DEMs validates the accuracy of deep sequencing. Experiments were then conducted to investigate their expression responses to BaP stress at different time intervals in detail to further determine their expression dynamic in responses of B. belcheri towards BaP exposure. This study, to the best of our knowledge, investigates the regulatory roles of miRNAs in the toxicological response of amphioxus for the first time, providing valuable information for the protection of lone existing cephalochordate amphioxus.

Characterization of transcriptional responses mediated by benzo[a]pyrene stress in a new marine fish model of goby, Mugilogobius chulae.

Benzo[a]pyrene (BaP) is one of the most studied targets among polycyclic aromatic hydrocarbons (PAHs). Because of the complexity of the toxicity mechanism in BaP, little is known about the molecular mechanism at the level of transcription of BaP in marine fishes. The primary objective of this study was to investigate the molecular basis of the effects of BaP on marine fish, using Mugilogobius chulae (Smith 1932) as the model. A closed colony of M. chulae was used for the BaP toxicity test. Two fish liver samples per replicate from each group were excised and blended into one sample by pooling an equal amount of liver tissue. Total RNA of all samples was extracted separately. Equal quantities of total RNA from the three replicates of the two groups were pooled for sequencing. The sequencing cDNA libraries were sequenced using Illumina HiSeq 2000 system. Differentially expressed genes were detected with the DEGSeq R package. In total, 52,364,032 and 53,771,748 clean nucleotide reads were obtained in the control and BaP-exposed libraries, respectively, with N50 lengths of 1277 and 1288bp, respectively. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analyses revealed a significant enrichment of genes related to detoxification, transportation, and lipid metabolism. We also identified, for the first time, an association between endoplasmic reticulum dysfunction and lipid metabolism resulting from BaP exposure. Using quantitative real-time PCR, some effective molecular biomarkers for monitoring of BaP-polluted seawater were identified. The results demonstrate that BaP enhanced the expression of genes involved in detoxification in M. chulae and inhibited that of genes related to lipid metabolism, possibly by suppressing the expression of numerous ER-related genes involved in fat digestion and absorption.

Transcriptional responses of Acropora hyacinthus embryo under the benzo(a)pyrene stress by deep sequencing

Coral embryos are a critical and sensitive period for the early growth and development of coral. Benzo(a)pyrene (BaP) is widely distributed in the ocean and has strong toxicity, but there is little information on the toxic effects to coral embryos exposed to this widespread environmental contaminant. Thus, in this study, we utilized the Illumina Hiseq™ 4000 platform to explore the gene response of Acropora hyacinthus embryos under the BaP stress. A total of 130,042 Unigenes were obtained and analyzed, and approximately 37.67% of those matched with sequences from four different species. In total, 2606 Unigenes were up-regulated, and 3872 Unigenes were down-regulated. After Gene Ontology (GO) annotation, the results show that the “cellular process” and “metabolic process” were leading in the category of biological processes, which the “binding” and “catalytic activity” were the most abundant subcategories in molecular function. Based on the Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, the most differentially expressed genes (DEGs) were enriched, as well as down-regulated in the pathways of oxidative phosphorylation, metabolism of xenobiotics, immune-related genes, apoptosis and human disease genes. At the same time, 388,197 of Single-nucleotide Polymorphisms (SNPs) and 6164 of Simple Sequence Repeats (SSRs) were obtained, which can be served as the richer and more valuable SSRs molecular markers in the future. The results of this study can help to better understand the toxicological mechanism of coral embryo exposed to BaP, and it is also essential for the protection and restoration of coral reef ecosystem in the future.