Study on hormone induction of the male parent and embryonic development, gonad differentiation, and growth of "All-female No.1" Culter alburnus.

Female Culter alburnus was faster in growth rate than males. In this study, the gynogenetic G2 and the pseudo-male G2' were used as the female and male parents, respectively, to breed a new national variety "All-female No.1" C. alburnus (AFC). Hormone induction, embryonic development, gonadal differentiation, and growth of AFC were studied. The results showed induction with low concentrations of 17α-methyltestosterone in a indoor-net cage culture was not effective. Under the stimulation of 17α-methyltestosterone, some gonads had a tendency to transform into testis, but not completely. There were three types of gonads in 5-month-old and four types of gonads in 12-month-old fishes, however, they all differentiated into ovaries in 15-month-old fishes. Testosterone propionate and high concentrations of 17α-methyltestosterone in pond culture induction had a good effect resulting in ①a functional pseudo-male with normal testis development that could successfully extrude semen during the breeding period, ②a pseudo-male with normal testis development, but could not extrude semen, and ③the appearance of intersexual glands. The second experiment revealed that with common fish, all-female fish embryo had normal embryonic development. The development time and morphological characteristics of each stage were similar, but the development of the all-female embryo was slightly slower than the common embryos. The gonad differentiation of the all-female embryo were normal and none differentiated into testis, which indicated that all-female could ensure the female sex without affecting the normal gonad differentiation. The correlation between body weight, length, and month-age of all-female and common fish was strong. The all-female had faster growth rate and more uniform growth specification than the common fish. Therefore, the use of testosterone propionate and high concentrations of 17α-methyltestosterone in pond culture induction could avoid complete degeneration of gonads into ovaries. The all-female embryo had the advantages of normal embryonic development and gonadal differentiation, faster growth, and uniform growth specification.

Effects of different conditions on the artificial incubation effect and physiological indexes of redclaw crayfish eggs.

We explored the effects of different conditions on the artificial incubation of redclaw crayfish eggs in an effort to improve this process. Samples at the egg and juvenile stages were selected. The samples at different stages were separated from the pleopods, then they were placed in incubator boxes and sterilized with different disinfectant solutions. The density was 300,400 and 500 eggs/incubator box, the vibration frequency was 11,16 and 26 vibrations/min, and the water circulation cycle was 2.1, 4.8 and 7.1 cycles/h. The results showed the eggs disinfected with 3000 ppm formaldehyde for 15 min had stronger antioxidant capacity. The hatching and survival rates of five pairs of appendage stage group were significantly lower than those of other groups. In the egg stage, acid phosphatase (ACP) level of compound eye pigmentation stage group was significantly higher than those of other groups. In the juvenile stage, malondialdehyde (MDA) content of five pairs of appendage stage group was significantly higher than those of other groups. The survival rate of 500 eggs/box group was significantly higher than that of other groups. In the egg stage, alkaline phosphatase (AKP) level of 400 eggs/box group was significantly higher than that of other groups. The survival rate of 11 vibrations/min group was significantly higher than that of other groups. In the egg stage, ACP and AKP levels of 11 vibrations/min group were significantly higher than those of 26 vibrations/min group. In the juvenile stage, superoxide dismutase (SOD), ACP and AKP levels of 11 vibrations/min group was significantly higher than those of 26 vibrations/min group. In the juvenile stage, AKP level of 4.8 cycles/h group was significantly lower than that of other groups. In conclusion, egg development at the stage after seven pairs of appendages, with a density of 400 eggs/box, vibration frequencies set at 11 vibrations/min achieved high hatching rates (93.58 %) and survival rates (75.67 %). Moreover, bronopol or hydrogen peroxide might have a better choice to replace formaldehyde if further exploration was conducted to reduce stimulation of the in vitro-grown egg. These conditions could be used on a large scale to optimize the production of redclaw crayfish.

Application of a recombinant replicase to localize the Trionyx sinensis hemorrhagic syndrome virus and evaluate its effects on antiviral genes of T. sinensis.

Trionyx sinensis Hemorrhagic Syndrome Virus (TSHSV) is an arterivirus newly discovered in Chinese softshell turtles. Little is known about the effect of antibodies against the virus or the distribution of the virus in different organs of infected turtles. In this study, a partial protein of TSHSV-HP4 was produced using a prokaryotic expression system, and its polyclonal antibody was generated. The polyclonal antibody was confirmed by western blot and dot enzyme-linked immunosorbent assay (dot-ELISA). The distribution of TSHSV in different organs of T. sinensis was examined by immunohistochemistry (IHC) and the expression of immune-related genes was analyzed using quantitative real-time polymerase chain reaction (qRT-PCR). The results indicated that the recombinant TSHSV-HP4 protein was successfully expressed, and the generated polyclonal antibody showed specific binding to viral particles in the lung tissues of infected turtles. The IHC assay indicated that the virus was highly localized in various cells, including intestinal lymphocytes, enterocytes, kidney epithelial cells, spleen cells, lung macrophages, and cardiomyocytes. The qRT-PCR analysis revealed that TSHSV was detected in all organs tested, including the lungs, liver, kidneys, spleen, and heart. The numbers of viral mRNA copies in lung and heart tissues were significantly higher in the virus-antibody group than in the virus group. The interferon-stimulated genes (ISGs), myxovirus resistance protein 2 (MX2) and radical S-adenosyl methionine domain containing 2 (RSAD2) were highly upregulated in all groups of infected turtles. Antibody-dependent enhancement (ADE) seemed to occur after stimulation by the polyclonal antibody, because significantly greater expression of the two genes was detected in the virus-antibody group than in the virus group. Overall, these results are important in understanding the cell localization of TSHSV and the immune response of infected turtles.

Complete genome sequence of novel isolate SYJ15 of Bacillus cereus group, a highly lethal pathogen isolated from Chinese soft shell turtle (Pelodiscus Sinensis).

SYJ15 is a highly pathogenic Gram-positive Bacillus sp. with top bud spore newly isolated from dying soft shell turtle. 16SrDNA sequencing showed that it is highly homologous to B. cereus, B. thuringiensis and B. anthracis. Biochemical examinations showed that it belongs to B. cereus. To further study the new pathogen, we conducted whole-genome sequencing based on single-molecular sequencing technology from PacBio. Genome assembly analysis showed that the strain has a 5,296,886 bp chromosome, a 218,649 bp plasmid and a 5221 bp plasmid with GC content of 35.51%, 31.91% and 29.75%, respectively. The genome contains 5736 coding sequences and 6 CRISPR systems located in the chromosome as well as 11 genomic islands in the chromosome and the large plasmid. Genome function analyses were annotated by nr database, SwissProt, KEGG, COG, GO, PHI, VFDB, ARDB, Secretory_Protein and T3SS. In addition, 13 gene clusters of secondary metabolism were predicted by antiSMASH. Comparison of SYJ15 with B. subtilis, B. anthracis, B. cereus and B. thuringiensis identified 1031 core genes of the five strains and 816 genes specific to SYJ15. In addition, SYJ15 had the most common core genes with B. thuringiensis, and the least with B. subtilis. Phylogenetic analysis demonstrated that SYJ15 is between B. thuringiensis and B. cereus, suggesting that SYJ15 belongs to Bacillus cereus group. We designed a specific primer pair to distinguish SYJ15 from B. pumilus, B. licheniformis, B.subtilis, B. thuringiensis and B. cereus. In conclusion, information of SYJ15 genome will help to enhance our understanding of pathogenesis of SYJ15 and find effective treatment.

Transcriptome profiling analysis of lung tissue of Chinese soft-shell turtle infected by Trionyx sinensis Hemorrhagic Syndrome Virus.

Trionyx sinensis Hemorrhagic Syndrome Virus (TSHSV) is the firstly discovered aquatic arterivirus inducing high mortality of Trionyx sinensis. So far, the lack of genomic resources has hindered further research on revealing the immunological characteristics of T. sinensis in response to TSHSV. In the present study, we performed a transcriptome analysis from the lungs of T. sinensis challenged by TSHSV using Illumina-based RNA-Seq. The validity of transcriptomic data was confirmed with the gradual increase of TSHSV RNA copies detected in lung. A total of 103079339 clean reads were generated, and 58374764 unique mapped reads were analyzed. Assembly of the sequence data allowed identifying 16383 unigenes consisting of 36 significant differentially expressed genes (DEGs). These DEGs were categorized into 30 GO-enriched bioprocesses and 9 KEGG pathways. The combinational analysis of GO-enriched bioprocesses and KEGG pathways demonstrated that TSHSV modulated several immune genes of T. sinensis related to various biological processes, including virus recognition (RIG-I/MDA-5), immune initiation (IFIT-1 and IFIT-5), endocytosis (CUBN, ENPP2 and LRP2) and steroid metabolism (FCNIL and STAR). In summary, the finding of this study revealed several immune pathways and candidated genes involved in the immune response of T. sinensis against TSHSV-infection. These results will provide helpful information to investigate molecular mechanism of T. sinensis in response to TSHSV.

Isolation and characterization of a novel strain (YH01) of Micropterus salmoides rhabdovirus and expression of its glycoprotein by the baculovirus expression system.

As one of the most important aquatic fish, Micropterus salmoides suffers lethal and epidemic disease caused by rhabdovirus at the juvenile stage. In this study, a new strain of M. salmoides rhabdovirus (MSRV) was isolated from Yuhang, Zhejiang Province, China, and named MSRV-YH01. The virus infected the grass carp ovary (GCO) cell line and displayed virion particles with atypical bullet shape, 300-500 nm in length and 100-200 nm in diameter under transmission electron microscopy. The complete genome sequence of this isolate was determined to include 11 526 nucleotides and to encode five classical structural proteins. The construction of the phylogenetic tree indicated that this new isolate is clustered into the Vesiculovirus genus and most closely related to the Siniperca chuatsi rhabdovirus. To explore the potential for a vaccine against MSRV, a glycoprotein (1-458 amino acid residues) of MSRV-YH01 was successfully amplified and cloned into the plasmid pFastBac1. The high-purity recombinant bacmid-glycoprotein was obtained from DH10Bac through screening and identification. Based on polymerase chain reaction (PCR), western blot, and immunofluorescence assay, recombinant virus, including the MSRV-YH01 glycoprotein gene, was produced by transfection of SF9 cells using the pFastBac1-gE2, and then repeatedly amplified to express the glycoprotein protein. We anticipate that this recombinant bacmid system could be used to challenge the silkworm and develop a corresponding oral vaccine for fish.

Complete genome sequence and analysis of a new lethal arterivirus, Trionyx sinensis hemorrhagic syndrome virus (TSHSV), amplified from an infected Chinese softshell turtle.

Trionyx sinensis hemorrhagic syndrome virus (TSHSV) is a newly discovered lethal arterivirus that causes serious disease in Trionyx sinensis in China. In this study, the complete genome sequence of TSHSV was determined by RACE cloning, and the functions of the predicted proteins were predicted. The complete genome of TSHSV was found to be 17,875 bp in length, and a 3'-end poly(A) tail was detected. Eight TSHSV hypothetical proteins (TSHSV-HPs) were predicted by gene model identification. TSHSV-HP2, 3 and 4 were associated with replicase activity, since papain-like protease (PLPs), serine-type endopeptidase, P-loop-containing nucleoside triphosphate hydrolase, and EndoU-like endoribonuclease motifs were detected. Phylogenetic analysis showed that TSHSV clusters with an arterivirus from a Chinese broad-headed pond turtle.