The acute neurotoxicity of inorganic mercury in Mactra chinensis philippi.

Inorganic mercury (IHg) is hazardous to marine organisms especially resulting in neurotoxicity, bivalves are sensitive to pollutants as "ocean sentinel", but data on the neurotoxicity of IHg in bivalves are sparse. So we chosed M. chinensis philippi with typical neural structures in bivalves to investigate the neurotoxicity of IHg, which could be helpful to understand the specificity of neural regulation and the response characteristics of bivalves. After acute exposed to IHg (HgCl2) for 24 h, the metabolites of ganglion tissues in M. chinensis philippi were evaluated using 1H-nuclear magnetic resonance based metabolomics; Ca2+, neurotransmitters (nitric oxide, glutamate, acetylcholine) and related enzymes (calcineurin, nitric oxide synthase and acetylcholinesterase) were measured using biochemical detection. Compared to the control group, the levels of the nitric oxide (81.04 ± 12.84 µmol/g prot) and acetylcholine (30.93 ± 12.57 µg/mg prot) in M. chinensis philippi of IHg-treated were decreased, while glutamate (2.11 ± 0.61 mmol/L) increased significantly; the activity of nitric oxide synthase (679.34 ± 135.33 U/mg prot) was increased, while acetylcholinesterase (1.39 ± 0.44 U/mg prot) decreased significantly, and the activity of calcineurin (0.52 ± 0.02 U/mg prot) had a statistically insignificant increasing tendency. The concentration of Ca2+ (0.92 ± 0.46 mmol/g prot) in the IHg-treated group was significantly higher than that in the control group. OPLS-DA was performed to reveal the difference in metabolites between the control and IHg-challenged groups, the metabolites of glucose, glutamine, inosine, succinate, glutamate, homarine, and alanine were sensitive to IHg, subsequently metabolic pathways that were affected including glucose metabolism, glutamine metabolism, nucleotide metabolism, Krebs cycle, amino acid metabolism and osmotic regulation. In our study, IHg interfered with metabolites in M. chinensis philippi, thus the corresponding metabolic pathways were changed, which influenced the neurotransmitters subsequently. Furthermore, Ca2+overload affected the synthesis or degradation of the neurotransmitters, and then the altered neurotransmitters involved in changes in metabolic pathways again. Overall, we hypothesized that the neurotoxic effects of IHg on bivalve were in close contact with metabolism, neurotransmitters, related enzymes and Ca2+, which could be effective neurotoxic biomarkers for marine environmental quality assessment, and also provide effective data for the study of the regulatory mechanism of the nervous system in response to IHg in bivalves.

Comparative proteomics study of exosomes in Vibrio harveyi and Vibrio anguillarum.

Exosomes are a class of extracellular vesicles released by bacteria and contain diverse biomolecules. In this study, we isolated exosomes from Vibrio harveyi and Vibrio anguillarum, which are both serious pathogens in mariculture, using a supercentrifugation method, and the proteins in the exosomes of these two vibrios were analyzed by LC-MS/MS proteomics. Exosome proteins released by V. harveyi and V. anguillarum were different; they not only contained virulence factors (such as lipase and phospholipase in V. harveyi, metalloprotease and hemolysin in V. anguillarum), but also participated in the important life activities of bacteria (such as fatty acid biosynthesis, biosynthesis of antibiotics, carbon metabolism). Subsequently, to verify whether the exosomes participated in bacterial toxicity, after Ruditapes philippinarum was challenged with V. harveyi and V. anguillarum, the corresponding genes of virulence factors from exosomes screened by proteomics were tested by quantitative real-time PCR. All the genes detected were upregulated which suggested that exosomes were involved in vibrio toxicity. The results could provide an effective proteome database for decoding the pathogenic mechanism of vibrios from the exosome perspective.

Understanding a Mechanistic Basis of ABA Involvement in Plant Adaptation to Soil Flooding: The Current Standing.

Soil flooding severely impairs agricultural crop production. Plants can cope with flooding conditions by embracing an orchestrated set of morphological adaptations and physiological adjustments that are regulated by the elaborated hormonal signaling network. The most prominent of these hormones is ethylene, which has been firmly established as a critical signal in flooding tolerance. ABA (abscisic acid) is also known as a "stress hormone" that modulates various responses to abiotic stresses; however, its role in flooding tolerance remains much less established. Here, we discuss the progress made in the elucidation of morphological adaptations regulated by ABA and its crosstalk with other phytohormones under flooding conditions in model plants and agriculturally important crops.

Molecular characterization, expression and immune functions of two C-type lectin from Venerupis philippinarum.

In the present study, two C-type lectins (designated as VpClec-3 and VpClec-4) were identified and characterized from the manila clam Venerupis philippinarum. Multiple alignment and phylogenetic relationship analysis strongly suggested that VpClec-3 and VpClec-4 belong to the C-type lectin family. In nonstimulated clams, the VpClec-3 transcript was dominantly expressed in the hepatopancreas, while the VpClec-4 transcript was mainly expressed in gill tissues. Both VpClec-3 and VpClec-4 mRNA expression was significantly upregulated following Vibrio anguillarum challenge. Recombinant VpClec-4 (rVpClec-4) was shown to bind lipopolysaccharide (LPS) and glucan in vitro, whereas recombinant VpClec-3 (rVpClec-3) only bound to glucan. In addition, rVpClec-3 and rVpClec-4 displayed broad agglutination activities towards Vibrio harveyi, Vibrio splendidus and V. anguillarum, while no agglutination activities towards Enterobacter cloacae or Aeromonas hydrophila were observed in rVpClec-3. Moreover, hemocyte phagocytosis was significantly enhanced by rVpClec-3 and rVpClec-4. All the results showed that VpClecs function as pattern recognition receptors (PRRs) with distinct recognition spectra and are potentially involved in the innate immune responses of V. philippinarum.

Antimicrobial Secondary Metabolites from the Seawater-Derived Fungus Aspergillus sydowii SW9.

Marine-derived fungi are considered to be valuable producers of bioactive secondary metabolites used as lead compounds with medicinal importance. In this study, chemical investigation of the seawater-derived fungus Aspergillus sydowii SW9 led to the isolation and identification of one new quinazolinone alkaloid, 2-(4-hydroxybenzyl)-4-(3-acetyl)quinazolin-one (1), one new aromatic bisabolene-type sesquiterpenoid, (2) and one new chorismic acid analogue (3), as well as two known alkaloids (compounds 4 and 5). Their structures were determined by extensive 1D/2D NMR and mass spectrometric data, and the absolute configurations of 2 and 3 were assigned by the analysis of ECD spectra aided by quantum chemical computations. Compounds 1, 2, and 4 exhibited selective inhibitory activities against the human pathogenic bacteria Escherichia coli, Staphylococcus aureus, S. epidermidis, and Streptococcus pneumoniae, with MIC values ranging from 2.0 to 16 µg/mL.

Genetic diversity and population structure of penis fish (Urechis unicinctus) based on mitochondrial and nuclear gene markers.

Urechis unicinctus is distributed only in Bohai Gulf of China and Korean and Japanese coast. The wild populations of this species have sharply declined in China and Japan. We collected 105 samples from six localities of Bohai Gulf and Korea coast, and investigated genetic diversity and population structure with mitochondrial COI, 16S-rRNA and nuclear 28S-rRNA gene fragments. Genetic diversity of U. unicinctus based on COI sequences was still high (Hd: 0.9595, π: 0.0101), however, 28S-rRNA gene sequences showed low level of genetic diversity (Hd: 0.4084, π: 0.0007). Based on COI sequences, FST values between populations ranged from -0.00204 to 0.05210, and 99.12% genetic diversity was contributed by different individuals within population. Both phylogenetic trees and median-joining network did not show clear geographic cluster, haplotypes from different populations were mixed. Our results indicated low level of genetic divergence among different localities of U. unicinctus, and this species should be treated as a whole population among China, Japan and Korea coast during species conservation.

Effects of potential probiotic Bacillus cereus EN25 on growth, immunity and disease resistance of juvenile sea cucumber Apostichopus japonicus.

This study was conducted to determine effects of potential probiotic Bacillus cereus EN25 (isolated from mud of sea cucumber culturing water bodies) on growth, immunity and disease resistance against Vibrio splendidus infection in juvenile sea cucumbers Apostichopus japonicus. Animals were respectively fed diets with B. cereus EN25 at 0 (control), 10(5), 10(7) and 10(9) CFU/g for 30 days. Results showed that dietary B. cereus EN25 had no significant effects on growth, total coelomocytes counts and acid phosphatase activity of A. japonicus (P > 0.05). Dietary EN25 at 10(7) CFU/g had significantly improved the phagocytosis, respiratory burst activity and total nitric oxide synthase activity of animals (P < 0.05). Compared to control, dietary EN25 at 10(5) or 10(7) CFU/g had no significant effects on superoxide dismutase activity of A. japonicus (P > 0.05), whereas dietary EN25 at 10(9) CFU/g had significantly decreased its activity (P < 0.05). The cumulative mortality after V. splendidus challenge decreased significantly in sea cucumbers fed with EN25 at 10(7) CFU/g (P < 0.05). The present study confirmed dietary B. cereus EN25 at 10(7) CFU/g could significantly improve immunity and disease resistance in juvenile A. japonicus.

Effects of potential probiotic Bacillus subtilis T13 on growth, immunity and disease resistance against Vibrio splendidus infection in juvenile sea cucumber Apostichopus japonicus.

A feeding experiment was conducted to determine influences of potential probiotic Bacillus subtilis T13 (isolated from intestine of healthy sea cucumbers) on growth, immunity and disease resistance against Vibrio splendidus infection in juvenile sea cucumbers Apostichopus japonicus. Animals were fed with diets containing B. subtilis T13 at 0, 10(5), 10(7) and 10(9) CFU/g for 30 days, respectively. At the end of the growth trial, fifteen sea cucumbers from each aquarium were sampled for immune indices measurement. Then twenty sea cucumbers from each replicate were challenged with V. splendidus. Results showed that administration of B. subtilis T13 had significant effect on the specific growth rates (SGR) of sea cucumbers (P < 0.05). Phagocytosis, respiratory burst activity and total nitric oxide synthase (T-NOS) activity were significantly improved in coelomocytes of sea cucumbers fed with T13 at 10(9) CFU/g diet (P < 0.05). The highest values of the total coelomocytes counts (TCC) and superoxide dismutase (SOD) activity were found in sea cucumbers fed diet containing T13 at 10(9) CFU/g. The cumulative mortality after V. splendidus challenge decreased significantly in sea cucumbers fed with T13 at dose of 10(9) CFU/g (P < 0.05). The present study confirmed the potential beneficial effects of B. subtilis T13 as dietary probiotic in juvenile A. japonicus.

Characterization of an ETS transcription factor in the sea scallop Chlamys farreri.

We have cloned and characterized a cDNA encoding a putative ETS transcription factor, designated Cf-ets. The Cf-ets encodes a 406 amino acid protein containing a conserved ETS domain and a Pointed domain. Phylogenetic analysis revealed that Cf-ets belongs to the ESE group of ETS transcription factor family. Real-time PCR analysis of Cf-ets expression in adult sea scallop tissues revealed that Cf-ets was expressed mainly in gill and hemocytes, in a constitutive manner. Cf-ets mRNA level in hemocytes increased drastically after microbial challenge indicated its indispensable role in the anti-infection process. Simultaneously, the circulating hemocyte number decreased. In mammals, most ETS transcription factors play indispensable roles in blood cell differentiation and linage commitment during hematopoisis. Cf-ets is therefore likely to be a potential biomarker for hematopoiesis studies in scallops.