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Phaeocystis globosa is an important unicellular eukaryotic alga that can also form colonies. P. globosa can cause massive harmful algal blooms and plays an important role in the global carbon or sulfur cycling. Thus far, the ecophysiology of P. globosa has been investigated by numerous studies. However, the proteomic response of P. globosa to nitrogen depletion remains largely unknown. We compared four protein preparation methods of P. globosa for two-dimensional electrophoresis (2-DE) (Urea/Triton X-100 with trichloroacetic acid (TCA)/acetone precipitation; TCA/acetone precipitation; Radio Immuno Precipitation Assay (RIPA) with TCA/acetone precipitation; and Tris buffer). Results show that the combination of RIPA with TCA/acetone precipitation had a clear gel background and showed the best protein spot separation effect, based on which the proteomic response to nitrogen depletion was studied using 2-DE. In addition, we identified six differentially expressed proteins whose relative abundance increased or decreased more than 1.5-fold (P<0.05). Most proteins could not be identified, which might be attributed to the lack of genomic sequences of P. globosa. Under nitrogen limitation, replication protein-like, RNA ligase, and sn-glycerol-3-phosphate dehydrogenase were reduced, which may decrease the DNA replication level and ATP production in P. globosa cells. The increase of endonuclease III and transcriptional regulator enzyme may affect the metabolic and antioxidant function of P. globosa cells and induce cell apoptosis. These findings provide a basis for further proteomic study of P. globosa and the optimization of protein preparation methods of marine microalgae. [ABSTRACT FROM AUTHOR]

Heavy metal lead (Pb) is a primary pollutant that pollutes aquatic environments and can be enriched in aquatic animals. Here, the effects of waterborne Pb on grass carp (Ctenopharyngodon idella) within 96 h of exposure were detected, and the association between microbiota alterations in the intestines and water was analysed. Results revealed that the intestinal barrier was damaged, including the intestinal morphology change, the structure‐related genes (villin‐1 and Claudin‐7) expression down‐regulation, the antioxidant (GST and GSH‐Px) and immune‐related genes (TNF‐α and IL‐8) expression up‐regulation. The MiSeq sequencing data revealed a decrease in diversity and an increase in microbiota richness in the intestines and water after Pb exposure. Linear discriminant analysis (LDA) results revealed an increase in the dominant bacteria (P_proteobacteria and C_Gammaproteobacteria) in the water, which enriched bacteria in the intestines. Canonical correlation analysis (CCA) found that there were correlations between intestinal microbiota and water microbiota, intestinal structure morphology and immune factors. Based on these results, we speculated that the effects of Pb on the grass carp intestinal barrier may be related to changes in the intestinal structure of grass carp and the water microbial community. These findings improve our understanding of the effects of heavy metals on the fish–microbe relationships after polluting aquatic habitats. [ABSTRACT FROM AUTHOR]

The major histocompatibility complex (MHC) genes play a key role in immune response in vertebrates. In this study, an MHC I alpha homolog gene (PfMHC Ⅰα) from pufferfish (Takifugu obscurus) was identified and its subcellular localization and expression patterns of PfMHC Ⅰα after challenge in vivo and in vitro were analysed. The open reading frame of PfMHC Ⅰα was 1,089 bp in length, encoding 362 aa. The immunofluorescence result revealed that PfMHC Ⅰα was presented on the membrane of lymphocytes. qRT‐PCR analysis indicated that PfMHC Ⅰα was expressed in all examined tissues, with the highest expression in skin, followed by the expression in gills and whole blood. After challenge of Aeromonas hydrophila or polyinosinic: polycytidylic acid (Poly I:C) in vitro, the expression levels of PfMHC Ⅰα on pufferfish kidney lymphocytes were significantly up‐regulated, with the highest expression level at 48 hr post‐challenge. After infection with A. hydrophila or Poly I:C in vivo, the expression levels of PfMHC Ⅰα in the skin, whole blood and kidneys were significantly up‐regulated. Taken together, it is speculated that PfMHC Ⅰα associates with resistance to both intracellular and extracellular antigens and plays an important role in the host response against pathogen infection in pufferfish. [ABSTRACT FROM AUTHOR]

Lead (Pb) is one of the most common trace metals in water, and its high concentration in the environment can cause harm to aquatic animals and humans. In the present study, the effects of Pb exposure (3.84 mg/kg) on the morphology, digestive enzyme activity, immune function and microbiota structure of silver carp (Hypophthalmichthys molitrix) intestines within 96 h were detected. Moreover, the correlation between them was analyzed. The results showed that Pb exposure on the one hand severely impaired the intestinal morphology, including significantly shortening the intestinal villi's length, increasing the goblet cells' number, causing the intestinal leukocyte infiltration, and thickening the intestinal wall abnormally, on the other hand, increasing the activity of intestinal digestive enzyme (trypsin and lipase). In addition, the mRNA expressions of structure-related genes (Claudin-7 and villin-1) were down-regulated, and the immune factors genes (IL-8 , IL-10 and TNF-α) were up-regulated after Pb exposure. Furthermore, data of the MiSeq sequencing showed that the abundance of membrane transport, immune system function and digestive system of silver carp intestinal microbiota all decreased, while cellular antigens increased. Finally, the canonical correlation analysis (CCA) showed that there were correlations between silver carp's intestinal microbiota and intestinal morphology and immune factors. In conclusion, it is speculated that the entry of Pb into the intestine leads the microbiota dysbiosis, affects the intestinal immunity and digestive function, and further damages the intestinal barrier of silver carp. [Display omitted] • Pb destroyed the intestinal barrier and affected the activity of digestive enzymes. • Pb induced intestinal microbiota dysbiosis in silver carp. • Pb changed the immune and digestive function of fish intestinal microbiota. • There was a correlation between the changes of bacteria and structure and function in intestine. [ABSTRACT FROM AUTHOR]

Lead (Pb) is an environmental pollutant that can accumulate in fish and humans. In this study, the effects of juvenile bighead carp (Hypophthalmichthys nobilis) on the intestinal structure, gut microbiota and cell apoptosis in the intestine of juvenile bighead carp (Hypophthalmichthys nobilis) after 96 h of Pb exposure were detected. The results showed that the intestinal barrier was severely damaged, including intestinal leukocyte infiltration, goblet cells significantly increased, intestinal villi shortened significantly, and abnormal thickening of the intestinal wall. Meanwhile, the mRNA expressions of structure related genes (villin-1 and Claudin-12) were down-regulated after Pb exposure, while pro-inflammatory factors (IL-8 and TNF-α) were up-regulated and peaked at 48 h. It shows that Pb causes intestinal inflammation and destroys intestinal structure. Furthermore, MiSeq sequencing data of the 16S rRNA gene V3-V4 region revealed a reduction in richness and diversity of intestine microbiota after Pb exposed. At the phylum level, the abundance of enteropathogenic bacteria (Proteobacteria and Bacteroidetes) were increased significantly whereas Firmicutes and Cyanobacteria were decreased significantly after exposed to Pb. A more in-depth analysis, at the genus level, a total of 40 intestinal microbes identified by operational taxonomic unit (OTU) analysis were obviously changed at 6 h, 48 h and 96 h after exposure to Pb, and the abundance of pathogenic bacteria such as Chryseobacterium also increased significantly. The functional prediction results of intestinal flora showed that the abundance of apoptosis was down-regulated after Pb exposure. It was consistent with the mRNA expressions of Bid , Caspase-2 , and Caspase-3 , indicating that apoptosis function of cells and intestinal flora was disturbed. Taken together, it is speculated that Pb may lead to the destruction of the intestinal barrier of bighead carp, leading to the disorder of the intestinal microbial community, which in turn promotes the occurrence of cell apoptosis. Our research provided some evidence for the association between microbiota dysbiosis and cell apoptosis after Pb exposure in the intestine of juvenile bighead carp. Unlabelled Image • Exposure to lead induced gut damage at molecular and structural levels. • Alteration in apoptosis were also observed after lead exposure. • Lead exposure affected the composition of the gut microbiota. • Changes in intestinal apoptosis level may be related to gut microbiota. [ABSTRACT FROM AUTHOR]

The effects of replacing fish meal (FM) with low‐gossypol cottonseed meal (LCSM) on the intestinal barrier in different segments (PI, proximal intestine; MI, middle intestine; DI, distal intestine) were studied in juvenile golden pompano (Trachinotus ovatus) using 6‐week feeding trials. FM of 0% (diet_1), 20% (diet_2), 40% (diet_3) and 60% (diet_4) was replaced by LCSM. The FM‐based diet (diet_1) containing 25% FM was used as control group. The intestinal morphology, mRNA expression of tight junction‐related genes (ZO‐1, Occludin, Claudin‐12), antioxidant enzyme‐related genes (CAT, GPx, GR, CuZnSOD) and non‐specific immune response‐related genes (IL‐8, TNF‐α, C4) and microbiota of different intestine segments were detected. The results showed that the number and length of microvilli and intestinal wall thickness decreased significantly in PI of diet_3 and diet_4 groups. Meanwhile, mRNA expression of Occludin, Clauding‐12 and C4 was up‐regulated in PI and DI of diet_3 group; the expression of GR and CuZnSOD was up‐regulated in PI and MI with increasing LCSM replacement; the expression of TNF‐α was up‐regulated in the three segments of diet_3 group. Further, 16S rRNA amplicon sequencing revealed a significant reduction in the richness and diversity of intestinal microbial in diet_3 and diet_4 groups. At the family level and genera level, the abundance of Nocardiaceae and Rhodococcus was up‐regulated in the three segments of diet_3 and diet_4 groups respectively. These results suggested that the replacement of LCSM by more than 20% causes the intestinal barrier function of juvenile golden pompano to be affected. These provide a reference for sustainable aquaculture. [ABSTRACT FROM AUTHOR]

Caspase-7 is a key effector caspase that takes part in apoptosis, inflammation, and in immune responses in mammals. To date, studies on the expression and functional characterization of caspase-7 upon apoptosis in teleosts are limited. Here, we identify a caspase-7 homolog (pfcasp-7) from pufferfish (Takifugu obscurus) and characterize its expression pattern during bacterial challenge. The open reading frame of pfcasp-7 is 942 base pairs in length, encoding a polypeptide of 313 amino acids. The deduced amino acid sequence is highly homologous to other known caspase-7 s, which contain a carboxyl-terminal catalytic domain and a pentapeptide active-site motif (192QACRG196). Quantitative real-time qPCR analysis indicated that pfcasp-7 is expressed in all examined tissues (kidney, blood, gills, gut, heart, spleen, liver, brain, and muscle), with the highest expression in the kidney (>117-fold higher than the lowest expression in muscle), followed by expression in the blood and gills. Challenging with Aeromonas hydrophila induced apoptosis in the blood and kidney and resulted in the significant upregulation of pfcasp-7 expression, which was consistent with the detection of apoptosis by flow cytometry. Pfcasp-7 expression was also upregulated in the kidney leukocytes following in vitro stimulation with lipopolysaccharide and inactivated A. hydrophila. Taken together, these results suggest that pfcasp-7 is involved in apoptosis in pufferfish after bacterial infection. • Caspase-7 homolog (pfcasp-7) was identified from pufferfish (Takifugu obscurus). • The expressions of pfcasp-7 were significantly up-regulated after Aeromonas hydrophila challenge in vivo and in vitro. • Pfcasp-7 participated in apoptosis in peripheral blood and kidney after A. hydrophila challenge. [ABSTRACT FROM AUTHOR]