Institute of Hydrobiology, Chinese Academy Of Sciences
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Identification of Dermocystidium anguillae Spangenberg, 1975 from the American eel Anguilla rostrata (Lesueur, 1817) and Chinese perch Siniperca chuatsi (Basilewsky, 1855)
No full textRecently, mass mortality of the American eel Anguilla rostrata (Lesueur, 1817) and Chinese perch Siniperca chuatsi (Basilewsky, 1855) caused by dermocystidiosis has occurred in China. In the present study, a Dermocystidium species from American eels and Chinese perch was identified. Sequence analysis revealed that the small subunit ribosomal DNA (SSU rDNA) of Dermocystidium specimens infecting American eels was identical to those of Dermocystidium specimens infecting Chinese perch, which indicates the conspecificity of these Dermocystidium specimens from different hosts. When the present Dermocystidium specimens infecting gills of American eels was compared with all reported Dermocystidium species, it is found that the present species has closely related host fish, identical infection site, and overlapped size with D. anguillae Spangenberg, 1975 described from gills of European eel A. anguilla (Linnaeus, 1758), which suggests these two Dermocystidium isolations from the American eels and European eels may be considered as same species. Surprisingly, BLAST search showed that all the newly obtained SSU rDNA of D. anguillae were most similar to that of D. fennicum Pekkarinen, Lom, Murphy, Ragan, Dykova, 2003 infecting common perch Perca fluviatilis Linnaeus, 1758. However, their sequence variation should be within the degree of intraspecific sequence variation, being 99.61% to 99.71% similarities, suggesting that D. fennicum is synonymous with D. anguillae. Phylogenetically, all species in the Dermocystidium genus were clustered in the Dermocystidium clade. However, Amphibiocystidium ranae Pascolini, Daszak, Cunningham, Fagotti, Tei, Vagnetti, Bucci et Rosa, 2003 infecting frog Rana esculenta Linnaeus, 1785. was also placed in this clade, which may either imply the non-monophyly of the species in the Dermocystidium or the requirement for further phylogenetic study on these two genera
Effects of deep placement of fertilizer on periphytic biofilm development and nitrogen cycling in paddy systems
No full textPeriphytic biofilms are commonly presented at the water-soil interface in paddy fields. Different fertilization methods can affect the concentration and distribution of nutrients in paddy fields and thus affect the development of periphytic biofilms. In this study, the roles of periphytic biofilms in nitrogen (N) cycling in paddy systems and how they are affected by different fertilization methods were studied using microcosm experiments. Microcosms were prepared using soil samples from a paddy field and treated with surface and deep fertilization under light and dark conditions. Surface fertilization under light condition promoted the development of periphytic biofilms, while deep fertilization under dark condition inhibited their development. The development of periphytic biofilms increased the pH and dissolved oxygen levels in the overlying water. Surface fertilization resulted in high N concentrations in the overlying water and the topsoil layers, which enhanced NH3 volatilization and nitrification-denitrification but inhibited N fixation. The development of periphytic biofilms reduced NH3 volatilization loss but increased nitrification-denitrification loss and the overall N loss in the paddy system. The results from this work suggest that the presence of periphytic biofilms in paddy fields could increase N loss by 3.10%-7.11%. Deep fertilization is an effective method to retard the development of periphytic biofilms in the paddy system and can potentially increase the overall N use efficiency
Transcriptional and subcellular characterization of interferon induced protein-35 (IFP35) in mandarin fish, Siniperca chuatsi
No full textInterferon (IFN)-stimulated genes (ISGs) exert multiple functions in immune system, and IFN-induced protein 35 (IFP35), which is a member of ISG, has been suggested to be involved in numerous cellular activities including the regulation of antiviral immunity in mammals. However, the role of IFP35 in fish innate immunity remains largely unknown. In the present study, we characterized the IFP35 gene in mandarin fish Siniperca chuatsi, which contains two conserved Nmi/IFP35 homology domains (NIDs) at C-terminus, but no leucine zipper motif, with its genomic DNA sequence consisting of eight exons and seven introns. High and constitutive mRNA level of IFP35 was observed in all examined tissues, with the highest level being observed in gills. Moreover, the IFP35 gene was significantly induced in vivo for 120 h following the infection of infectious spleen and kidney necrosis virus (ISKNV), and its mRNA and protein level was also significantly induced in vitro following the treatment of poly I: C, IFNh, IFNc, as well as IFN-gamma. The subcellular localization results indicated that exogenous IFP35 protein was mainly located in cytoplasm, while endogenous IFP35 protein was transferred into, or aggregated around, the nucleus with the induction of poly I:C or IFNs. The dual luciferase activity analysis indicated that the IFP35 promoter was activated by type I and type II IFNs through ISRE site. It is considered that IFP35 in fish is involved in antiviral, as well as in IFN-induced innate immunity
TBK1 regulates the induction of innate immune response against GCRV by phosphorylating IRF3 in rare minnow (Gobiocypris rarus )
No full textRare minnow (Gobiocypris rarus), a small cyprinid species that is highly sensitive to the grass carp reovirus (GCRV), is regarded as an ideal model to study the mechanisms of innate immunity in fish. In the present study, a TBK1 homologue from rare minnow (GrTBK1) was identified and its roles in defence against viral infection were investigated. Sequence analysis showed that GrTBK1 encoded a 727-amino acid peptide which shared 98% and 72% identity to the black carp (Mylopharyngodon piceus) and human (Homo sapiens) orthologues, respectively. The amino acid sequence analysis demonstrated that GrTBK1 contains a conserved Serine/Threonine protein kinases catalytic domain (S_TKc) at the N-terminus. Furthermore, cellular distribution proved that GrTBK1 was located in the cytoplasm region. Quantitative real-time PCR analysis revealed that GrTBK1 was ubiquitously expressed in all examined organs, but especially highly in liver. Temporal expression analysis in vivo showed that the expression levels of GrTBK1 were obviously up-regulated in response to GCRV infection. Meanwhile, qRTPCR assay revealed that the levels of S7 RNA, an important segment of GCRV genome, were higher in the liver than in other tissues. This indicates that GrTBK1 might play a crucial role in responses to GCRV infection in fish. In addition, GrTBK1 activated several type I interferon (IFN) promoters and induced the expression of downstream type I IFN-stimulated genes (ISGs). Furthermore, GrTBK1 obviously phosphorylated the interferon regulatory factor 3 (IRF3). Furthermore, overexpression of GrTBK1 remarkably decreased the GCRV proliferation. In summary, we systematically characterized GrTBK1 and illustrated its role in the innate immune response to GCRV infections
The agrochemical S-metolachlor disrupts molecular mediators and morphology of the swim bladder: Implications for locomotor activity in zebrafish (Danio rerio)
No full textMetolachlor herbicides are derived from the chloroacetamide chemical family of which there are the Sand Rmetolachlor isomers. S-metolachlor is a selective herbicide that inhibits cell division and mitosis via enzyme interference. The herbicide is used globally in agriculture and studies report adverse effects in aquatic organisms; however, there are no studies investigating sub-lethal effects of S-metolachlor on swim bladder formation, mitochondrial ATP production, nor light-dark preference behaviors in fish. These endpoints are relevant for larval locomotor activity and metabolism. To address these knowledge gaps, we exposed zebrafish embryos/larvae to various concentrations of S-metolachlor (0.5-50 mu M) over early development. S-metolachlor affected survival, hatching percentage, and increased developmental deformities at concentrations of 50 mu M and above. Exposure levels as high as 200 mu M for 24 and 48 h did not alter oxygen consumption rates in zebrafish, and there were no changes detected in endpoints related to mitochondrial oxidative phosphorylation. We observed impairment of swim bladder inflation at 50 mu M in 6 dpf larvae. To elucidate mechanisms related to this, we measured relative transcript abundance for genes associated with the swim bladder (smooth muscle alpha (alpha)-2 actin, annexin A5, pre-B-cell leukemia homeobox 1a). Smooth muscle alpha (alpha)-2 actin mRNA levels were reduced in fish exposed to 50 mu M while annexin A5 mRNA levels were increased in abundance, corresponding to reduced swim bladder size in larvae. A visual motor response test revealed that larval zebrafish exhibited some hyperactivity in the light with exposure to the herbicide and only the highest dose tested (50 mu M) resulted in hypo activity in the dark cycle. Regression analysis indicated that there was a positive relationship between surface area of the swim bladder and distance traveled, and the size of the swim bladder explained similar to 10-14% in the variation for total distance moved. Lastly, we tested larvae in a light dark preference test, and we did not detect any altered behavioral response to any concentration tested. Here we present new data on sublethal endpoints associated with exposure to the herbicide S-metolachlor and demonstrate that this chemical may disrupt transcripts associated with swim bladder formation and morphology, which could ultimately affect larval zebrafish activity. These data are expected to contribute to further risk assessment guidelines for S-metolachlor in aquatic ecosystems
A novel phosphoinositide kinase Fab1 regulates biosynthesis of pathogenic aflatoxin in Aspergillus flavus
No full textAspergillus flavus (A. flavus) is one of the most important model environmental fungi which can produce a potent toxin and carcinogen known as aflatoxin. Aflatoxin contamination causes massive agricultural economic loss and a critical human health issue each year. Although a functional vacuole has been highlighted for its fundamental importance in fungal virulence, the molecular mechanisms of the vacuole in regulating the virulence of A. flavus remain largely unknown. Here, we identified a novel vacuole-related protein in A. flavus, the ortholog of phosphatidylinositol-3-phosphate-5-kinase (Fab1) in Saccharomyces cerevisiae. This kinase was located at the vacuolar membrane, and loss of fab1 function was found to affect the growth, conidia and sclerotial development, cellular acidification and metal ion homeostasis, aflatoxin production and pathogenicity of A. flavus. Further functional analysis revealed that Fab1 was required to maintain the vacuole size and cell morphology. Additional quantitative proteomic analysis suggested that Fab1 was likely to play an important role in maintaining vacuolar/cellular homeostasis, with vacuolar dysregulation upon fab1 deletion leading to impaired aflatoxin synthesis in this fungus. Together, these results provide insight into the molecular mechanisms by which this pathogen produces aflatoxin and mediates its pathogenicity, and may facilitate dissection of the vacuole-mediated regulatory network in A. flavus
Species-specific responses of submergedmacrophytes to the presence of a small omnivorous bitterling Acheilognathus macropterus
No full textRecovery of submerged macrophytes has been considered a key factor in the restoration of shallow eutrophic lakes. However, in some subtropical restored lakes, small omnivorous fish dominate the fish assemblages and feed in part on submerged macrophytes. Knowledge of the effects of small omnivores on the growth of submerged macrophytes is scarce and their responses are potentially species-specific, i.e. the growth of some species may be hampered by fish grazing while growth of others may be promoted by the nutrients becoming available by fish excretion. We conducted mesocosm experiments to examine the effects of the small omnivorous bitterling Acheilognathus macropterus, a common species in restored subtropical lakes in China, on nutrient concentrations and the growth of four species of submerged macrophytes (Hydrilla verticillata, Vallisneria denseserrulata, Ceratophyllum demersum and Myriophyllum spicatum). We found that the bitterling significantly increased nutrient concentrations via excretion and thereby enhanced the net growth of the less grazed nuisance macrophyte M. spicatum. In contrast, the net growth of C. demersum was reduced by the bitterling, most likely due to grazing as indicated by gut content analyses. Dominance by bitterling may, therefore, pose a threat to the long-term success of lake restoration by provoking a shift in the submerged macrophyte community towards nuisance species through selective grazing. Nutrient excretion may potentially also stimulate the growth of phytoplankton and periphyton, hampering the growth of submerged macrophyte. (C) 2020 Elsevier B.V. All rights reserved
Reduction in the phytoplankton index of biotic integrity in riverine ecosystems driven by industrial activities, dam construction and mining: A case study in the Ganjiang River, China
No full textIndustrial activities, dam construction, and mining are three human activities important for societal and economic development. However, the effects of these activities on phytoplankton communities have been less quantitatively assessed than those on other groups, such as macroinvertebrates, fish, and periphytic algae. In the present study, we selected the Ganjiang River basin, a tributary of the Yangtze River as the representative area to develop a feasible phytoplankton index of biotic integrity (Phyto-IBI) to evaluate the effects of industrial activities, dam construction, and mining on the biotic integrity of riverine ecosystems. The results showed that the three activities greatly altered the abundance and composition of phytoplankton, with a reduction in phytoplankton species quantity and diversity and an increase in abundance. The health status of the Ganjiang River was fair, and the health statuses of industrial areas, dam areas, mining areas, and reference points were poor, poor, fair, and good, respectively. The three activities damaged the biotic integrity of the aquatic system. Moreover, compared to industrial activities and mining, dam construction is more harmful to aquatic systems in the Ganjiang River. The locally weighted regression scatter plot smoother (LOWESS) method showed that an ammonium nitrogen (NH3-N) concentration of 0.65 mg L-1 is the environmental protection threshold for planktonic biotic integrity in the Ganjiang River. This study not only quantitatively assesses phytoplankton responses to industrial activities, dam construction, and mining but also provides guidance regarding the ecological monitoring, assessment and protection of riverine ecosystems
The new chimeric chiron genes evolved essential roles in zebrafish embryonic development by regulating NAD(+) levels
No full textThe origination of new genes is important for generating genetic novelties for adaptive evolution and biological diversity. However, their potential roles in embryonic development, evolutionary processes into ancient networks, and contributions to adaptive evolution remain poorly investigated. Here, we identified a novel chimeric gene family, the chiron family, and explored its genetic basis and functional evolution underlying the adaptive evolution of Danioninae fishes. The ancestral chiron gene originated through retroposition of nampt in Danioninae 48-54 million years ago (Mya) and expanded into five duplicates (chiron1-5) in zebrafish 1-4 Mya. The chiron genes (chirons) likely originated in embryonic development and gradually extended their expression in the testis. Functional experiments showed that chirons were essential for zebrafish embryo development. By integrating into the NAD(+) synthesis pathway, chirons could directly catalyze the NAD(+) rate-limiting reaction and probably impact two energy metabolism genes (nmnat1 and naprt) to be under positive selection in Danioninae fishes. Together, these results mainly demonstrated that the origin of new chimeric chiron genes may be involved in adaptive evolution by integrating and impacting the NAD(+) biosynthetic pathway. This coevolution may contribute to the physiological adaptation of Danioninae fishes to widespread and varied biomes in Southeast Asian
Grass carp cGASL negatively regulates interferon activation through autophagic degradation of MAVS
No full textIn mammals, cyclic GMP-AMP synthase (cGAS) is a crucial cytosolic DNA sensor responsible for activating the interferon (IFN) response. A cGAS-like (cGASL) gene was previously identified from grass carp Ctenopharyngodon idellus, which is evolutionarily closest to cGAS but not a true ortholog of cGAS. Here, we found that grass carp cGASL targets mitochondrial antiviral signaling protein (MAVS) for autophagic degradation to negatively regulate fish IFN response. Firstly, the transcriptional level of cellular cgasl was upregulated by poly I:C stimulation, and overexpression of cGASL significantly decreased poly I:C- and MAVS-induced promoter activities and transcriptional levels of IFN and IFN-stimulated genes (ISGs). In addition, cGASL associated with MAVS and prompted autophagic degradation of MAVS in a dose-dependent manner. Finally, overexpression of cGASL attenuated MAVS-mediated cellular antiviral response. These results collectively indicate that cGASL negatively regulates fish IFN response by triggering autophagic degradation of MAVS