Abstract:In order to explore the characteristics of glycogen content in Sinonovacula constricta, the glycogen synthase (sc-gys) gene and its feasibility in molecular marker-assisted breeding, the annual changes of glycogen content were detected in this study. The glycogen content in S. constricta was high between February to June and reached the maximum level in April during the annual cycle. The sc-gys gene has a full-length cDNA of 2 402 bp and an ORF of 2 136 bp, encoding 711 amino acids, with high similarity to orthologs of other animals showing conserved domain of Glycosyltransferase. The results of real-time quantitative PCR showed that sc-gys was mainly expressed in mantle and foot tissues. The expression level of sc-gys in April was significantly higher than that of other months, indicating its close relation to glycogen synthesis. Two SNP loci was tightly associated with glycogen content in the sc-gys exon region from "Yongle NO.1" new strain and wild population of Taizhou, and there was no linkage disequilibrium between the two SNP loci. Glycogen content of individuals with these two genotypes combinations was 11.8% higher than that of the population average. These two SNP loci and proper combination would provide candidate genetic markers for glycogen content genetic improvement of S. constricta.

Abstract:Growth traits are important economic traits in genetic breeding of aquaculture species. The combination of trait-related molecular markers and breeding can greatly accelerate the breeding process. In our previous research on the growth traits of Ctenopharyngodon idella, using the method of QTL mapping, we found two growth-related QTLs in the linkage group 1. Based on this, two pairs of the two QTL flanking markers (CID391_2, CID1512, CID973_1, and CID254_1) were used to analyze the 480 individuals of C. idella in the Yangtze River system in order to verify these microsatellite markers associated with growth traits in selected populations of grass carp. The results showed that:① the four microsatellite markers were highly polymorphic in this population (PIC> 0.50), among which the number of observed alleles (N_a) at each locus was 12 to 23, and the number of effective alleles (N_e) was 4 to 12, the observed heterozygosity (H_o) was 0.607-0.904, and the expected heterozygosity (H_e) was 0.751-0.902; ② by means of One-Way Analysis and multiple comparisons of the genotypes and the growth traits (body weight and body length) in the selected populations of C. idella, CID391_2 showed no significant difference between genotypes and the two growth traits in female individuals, while there was significant difference between genotypes and the two growth traits in male individuals; CID1512, CID973_1 and CID254_1 showed significant differences between each genotype and the two growth traits in female or male individuals. This study has verified microsatellite markers associated with growth traits in selected populations of C. idella. It will provide a basis for further research on QTL mapping in C. idella and the practice of molecular marker assisted selection (MAS) based on QTL mapping.

Abstract:Chinese sturgeon (Acipenser sinensis) is an endemic, endangered and protected anadromous fish in China. This fish has been listed as a Category I nationally protected species in China and a critically endangered (CR) species of the International Union for Conservation of Nature (IUCN). Due to the restrictions by several special reasons of this species, e.g., long lifespan, complex migratory process, and precarious resource situation, it is quite difficult to objectively reveal the features of life history, and characteristics of distribution, and dynamics of habitat use (e.g., spawning/nursery site) by some traditional methods. Consequently, introducing more new innovative approaches is needed to achieve new breakthrough on research of migratory ecology and conservation for this species. In the present study, microchemical characteristics of three kinds of hard tissues of A. sinensis (i.e., otolith, dorsal scute, and pectoral fin ray) were studied comparatively by electron probe microanalyses (EPMA) and laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) with their microstructure. The results show that otoliths of A. sinensis are loose in structure and contain small sand-like microcrystalline vaterite spherulites with independent core areas. In constrast, the dorsal scute is a stratified tissue while the pectoral fin ray is a relatively compact and uniform tissue. Viewed from the microchemical results of the three hard tissues, the analytical accuracy across all samples was high for Mg, Ti, V, Mn, Cu, Zn, Co, Sr, Ba and Ca with RSD<10%. The z-Scores of habitat element ratios for Co/Ca, Sr/Ca and Ba/Ca in both pectoral fin ray (-0.97-2.16, -0.78-2.56, -0.96-2.41) and otolith (-1.7-0.74, -1.24-0.98, -1.09-1.09) are consistent, while those z-Scores in the dorsal scute (-1.95-2.32, -1.68-2.03, -1.62-2.68) are fluctuative due to its stratification. At the same time, the microchemical maps of Sr, Ca and Ba in these three hard tissues revealed that pectoral fin ray and dorsal scute were uniform color/concentration while different parts of otolith showed different colors/concentrations. Based on the aforementioned findings and we consider practical needs from no lethality, difficulty of sampling and sample preparation process, tissular microstructure composition, and environmental element bioaccumulation. In the present study, the microstructure and microchemical characteristics of three kinds of hard tissues of A. sinensis, i.e., otolith, dorsal scute, and pectoral fin ray, were studied comparatively. The present study suggested that the pectoral fin ray is the best hard tissue material for microchemical study for reconstructing the history of the migration and life cycle of A. sinensis.

Abstract:In order to identify genes associated with growth traits and SNP (Single nucleotide polymorphism) markers in Ctenopharyngodon idella, RNA-Seq (RNA Sequencing technology) was used to analyze the transcriptomes of liver, muscle and brain tissues of fast-growing and slow-growing C. idella groups. A total of 314.65 million clean reads were gained for the fast-growing and slow-growing groups, and 34 147 unigenes were assembled, with an average length of 1 060 bp, of which 30 751 genes were annotated. 1 013, 552, and 372 significant differentially expressed genes were screened in liver, muscle, and brain tissues, respectively, of which 4 580 SNP markers were detected. Then, the polymorphisms of 34 SNP markers was detected and validated with SNaPshot technique in the extreme populations of growth traits of C. idella (n=300), and among which, 30 SNPs (83.24%) were successfully genotyped. A general linear model was used to analyze the correlation between 30 SNPs and growth traits. The results showed that at the position of Unigene00810126-8014, the body weight, body length, body height, head length and caudal peduncle length in individuals with CC genotype had significantly higher values than TT genotype. At the position of Unigene00810126-2903, the body weight of AA genotype was significantly higher than those with GG genotype. At the position of Unigene00870394-525, individuals with the AA genotype had significantly higher values in body weight and body height than those with GG genotype. At the position of Unigene02938762-011628, TT and CC genotypes had significant differences in body mass, body length and head length traits. Besides, other SNPs loci were not significantly correlated with growth traits. The four selected markers were located at Somatolactin alpha (slα), Early growth response protein-1 (egr-1) and Myosin heavy chain (myh) genes. The average polymorphism information content (PIC), average expected heterozygosity (H_e) and average observed heterozygosity(H_o) of 8 EST-SNP markers in C. idella population were 0.300, 0.377 and 0.363, respectively, indicating that genetic diversity of C. idella breeding population had relatively high level. In conclusion, 1 937 differentially expressed genes and four SNP markers related to growth traits were obtained, which can be used as candidate genes and for molecular marker-assisted selection of C. idella, and can also be used in subsequent breeding work.

Abstract:Functional groups are the foundation of the analysis of food web structure and energy flow in marine ranching ecosystems. Based on filed investigation in Wanshan Islands adjacent sea in 2016 and 2017, and historical data of fishery resources in the Pearl River Estuary, the predominance, biomass and catch rate of fishery resources were studied. The results showed that Caranx kalla, Collichthys lucidus, Metapenaeus joyneri, Eucrate crenata, Coilia mystus, Oratosquilla oratoria, Eucrate solaris and Charybdis acuta were the shared economical species from the top 30 economic species. In terms of feeding habit, seven groups were identified in Pearl River Estuary including zooplanktivores, zooplanktivores/benthivores, benthivores, benthivores/piscivores, piscivores, omnivores, and detritivores. And benthivores (34%) and zooplanktivores (20%) groups were dominant in the Pearl River Estuary. Furthermore, rare fishes, high-yield fishes and shrimp and crab were eventually selected as top economic species of key functional groups in marine ranching fishery resources including Pampus argenteus, E. moara, L. japonicas, N. albiflora, Mugil cephalus, Penaeus monodon, and Scylla serrate. The common features are:(i) native economic species; (ii) great body weight and high yield; (iii) delicious taste and high market value; (iv) capable of artificial reproduction and release; (v) different habitat water layers; (vi) mutualistic. According to tropic levels of these top economical species in food chain, we found that both Epinehelus moara and Nibea albiflora belong to the higher carnivorous species. Epinehelus moara are bottom fishes that mainly feed on small and medium-sized fish, crustaceans and cephalopods, while Nibea albiflora are middle and lower-layer fishes that mainly feed on small and medium-sized fishes (e.g., Decapterus maruadsi, Sardinella aurita) and shrimps (e.g., O. oratoria, Alpheus japonicas). In addition, Pampus argenteus, Lateolabrax japonicas and S. serrate belong to the intermediate carnivorous species. To be specific, Pampus argenteus are pelagic fish, mainly feeding on jellyfish, ripple worms, water fleas or other zooplankton. L. japonicas are bottom fishes that mainly feed on fishes (e.g., C.mystus, Setipinna taty) and crustaceans (e.g., Oratosquilla oratoria. Scylla serrate) are benthic crustacean and feed on mollusks and small crustaceans. Moreover, M. cephalus inhabits the middle and lower layers and belongs to lower carnivorous species, mainly feeding on debris or diatoms. And Penaeus monodon are bottom-layer omnivorous species that mainly feed on mollusks and zooplankton. In conclusion, we constructed seven key functional groups of marine ranching fishery resources composed of top economic species and organisms in their food chains, including P. argenteus functional groups, Epinehelus moara functional groups, L. japonicas functional groups, N. albiflora functional groups, M. cephalus functional groups, P. monodon functional groups and S. serrata functional groups. The above seven key functional groups can realize poly-dimension utilization of space-time resources in marine ranching, thus are of great importance for sustainable development of marine fisheries and healthy coastal ecosystems.

Abstract:In order to explore the influence of the position of the water inlet device on the hydrodynamic characteristics of the single-drain rectangular arc angle aquaculture tank, a new parameter, the relative inflow distance C/B (C is the horizon distance from inlet to sidewall, B is the width of the rectangular tank) was proposed in this paper, and the complex flow field of near the sewage outlet were analyzed by fluid dynamics characteristics variables, and to measure the effective utilization rate of water in aquaculture tank, the effective utilization coefficient of energy ηe is put forward. Meanwhile based on the Reynolds averaged Navier Stokes (RANS) equation and RNG k-ε turbulence model, a three-dimensional numerical model of rectangular arc angle aquaculture tank was constructed. Computational fluid dynamics simulation technology was used to calculate and analyze the flow field environment in the constructed aquaculture tank. By adjusting the layout position of the inlet system, the flow field in the tank (especially at the bottom) was optimized, and the influence of the optimization of hydrodynamic conditions on the collection and discharge performance of the aquaculture tank system was analyzed. This base case is validated against the experimental velocity measurements using Acoustic Doppler Velocimetry (ADV) at predefined locations across the central vertical plane of the tank. On this basis, the hydrodynamic conditions of the aquaculture tank system were systematically analyzed by hydrodynamic characteristics, such as the average velocity, energy efficiency, velocity distribution uniformity at the bottom of the tank and so on. The numerical simulation results show that the average velocity and energy efficiency can be significantly improved by optimizing the relative inflow distance, which is conducive to the formation of uniform and stable flow field. And increasing the relative inflow distance parameter C/B from 0.00 to 0.05 can effectively improve the flow field characteristics in the aquaculture tank, and setting the relative inflow distance parameter C/B between 0.02 and 0.04 is beneficial to obtain the best flow field conditions for the single channel rectangular arc angle aquaculture tank system.The results show that the ratio parameter C/B in the range of 0.02~0.04 could effectively improve flow field characteristics of the system so as to get better hydrodynamic conditions for circulating aquaculture, and relatively minor construction changes could improve the hydrodynamic conditions of the aquaculture system and open up new ideas for obtaining the hydrodynamic environment conducive to fish welfare and production operation.

Abstract:Acanthopagrus latus is a valuable marine fish and an important economic fish for marine aquaculture along the South China coast. In order to ascertain the genetic diversity and genetic differentiation status of A. latus populations distributed along the South China coast, in this study, the mitochondrial control region (D-loop) gene sequences were used to analyze the genetic diversity and population genetic structure of eight A. latus populations from the South China coast, including Xiamen, Shanwei, Yangjiang, Haikou, Sanya, and Beihai, Qinzhou, Qinzhou and Fangcheng. The results showed that 320 D-loop sequences from the eight A. latus populations were 947-958 bp in length. Totally, 29 insertion or deletion sites and 210 mutation sites (including 142 parsimony information sites and 68 single mutation sites) were detected in the D-loop sequences; overall mutation sites, haplotype number, and haplotype diversity (H_d), average nucleotide difference and nucleotide diversity (π) were 210, 268, 0.998 43, 14.790 65 and 0.01570, respectively. The results of cluster analysis showed that all populations were clustered into two groups, east and west separated by Qiongzhou Strait. The genetic differentiation coefficient (F_ST) between the eight populations was –0.01268-0.466 74, and gene flow (N_m) was 0.571 26~∞. The variance analysis showed that the genetic variation between groups, between populations within groups, and between individuals within populations were 33.42%, 0.32%, and 66.26%, respectively. Neutral tests showed that Tajima's D was –1.694 77 (P=0.010 00) and Fu 's Fs was –23.683 39 (P=0.00600), indicating that A. latus along the South China coast experienced a population expansion event. This study indicated that the genetic diversity of A. latus populations along the South China coast was relatively rich. This study suggested that A. latus populations can be divided into two management units by the Qiongzhou Strait, the east group and the west group for germplasm protection. Based on such monitoring results, some countermeasures and suggestions for the future restoration strategy were proposed so as to provide a theoretical basis for restoring and protecting the A. latus populations, and meanwhile it can also provide some scientific guidance for artificial breeding and value-added release in natural sea area.

Abstract:The integrated rice-field aquaculture (IRFA) has been practiced successfully for 2000 years in China. The integrated rice-crayfish (Procambarus clarkii) co-culture (IRCC) has contributed more than 50% of the yield of IRFC, currently. Thus it is necessary to conduct researches on the IRCC, including its' environmental impacts. As commercial feed feeding is very popular in IRCC practice, one of the potential environmental problems is the effects of feeding on the water and soil quality. Some previous studies have indicated that most nitrogen and phosphorus in the feed deposit in soil of crustacean aquaculture system. While it is not clear whether IRCC can increase nitrogen and phosphorus in soil, even some researches have been done. And it's also not clear the effects of IRCC on the metal element contents in soil. The purpose of this study was to evaluate the impacts of IRCC in soil fertility (nitrogen, phosphorus and organic matter contents), and metal element contents on soil. Six physicochemical indicators and 11 metal elements contents of three layers of soil (0-10 cm, 10-20 cm and 20-30 cm) of the trench (TRC) and paddy (PRC) of IRCC, and rice monoculture fields (RM, as control) in Qianjiang City, Hubei Province, China, were measured, and the culture ages of the two modes were both 5 years. Contents of soil organic matter (SOM) and available phosphorus (AP) were measured by potassium dichromate heating oxidation-volumetrics, and NaHCO₃ extraction, ammonium molybdate-tartaric emetic-ascrbic acid colorimetry method, respectively. Contents of total nitrogen (TN), ammonia nitrogen ($ {\rm{NH}}_4^ + $-N), nitrate ($ {\rm{NO}}_3^-$-N) and total phosphorus (TP) were measured by flow injection analysis, and contents of Cr, Cu, Cd, Pb, Zn, Ni, As, Fe, Mg, Ca and Mn were measured by microwave digestion-inductively coupled plasma-mass spectrometry. The contents of Cr, Cd, Pb, Zn, Ni, As and Cu were then evaluated according to the risk screening values for soil contamination of agricultural land in <GB15618-2018>. The results showed that the TN, $$AP and TP content of all layers exhibited a trend of PRC > RM > TRC, while SOM (excepting 20-30 cm layer) and NH₄⁺-N of RM > PRC > TRC and $ {\rm{NO}}_3^-$-N of TRC > PRC > RM. The content of Cu, As, Mg and Mn of all soil layers showed a trend of TRC > PRC > RM, while Cd, Pb, Fe and Ca on the contrary, and less significant differences were noted among TRC, PRC and RM for Cr, Zn or Ni, excepting for 0-10 cm longer. According to the risk screening values for soil contamination of agricultural land in <GB15618-2018>, Cr, Cd, Pb, Zn, Ni and As contents were up to standard, while Cu content was generally out of the limits, with over-limit ratios of 14%-46%. The results indicate that integrated rice-crayfish co-culture could increase nitrogen and phosphorus contents in the paddy soil, while decrease those in the trench soil, and SOM content.

Abstract:CBX2 (Chromobox homolog2), as a key member of the Polycomb Group protein (PcG) family, plays an important role in gonadal development. Mice lacking cbx2 showed defects in gonads (both ovary and testis) development, and some mice have exhibited male-to-female sex reversal. But little is known about the function of cbx2 in gonadal development of fish. In this study, we used Oryzias latipes, a model organism, to investigate the expression of cbx2 during embryonic and gonadal development by real-time PCR and immunohistochemistry. Real-time PCR results showed that cbx2 was highly expressed in embryos at gastrula, neurula and organogenesis stages. In bisexual gonads, cbx2 had a relatively high expression in testis. Immunohistochemistry results revealed that cbx2 mRNA was mainly localized in spermatogonia and spermatocytes in testis. And cbx2 was also predominately observed in oocytes at stages I, II and III in ovary. In order to further study the function of cbx2, we used microinjection technology to knock out cbx2. The results showed that the expression of cbx2 was significantly decreased after injecting siRNA, and thus the expression of sox9 (SRY-related HMG box 9) was down-regulated, whereas the expression of foxl2 (Forkhead transcriptional factor 2) increased. This indicated that cbx2 was not only involved in embryonic development but also played a role in gonadal differentiation and gametogenesis in O. latipes.

Abstract:Aeromonas spp. are gram-negative bacteria that can infect a variety of aquatic and terrestrial animals, including humans and cause motile aeromonad septicemia. The prevalence of Aeromonas spp. in various water and food sources poses a significant public health threat. Aeromonas spp. encompass a diversity of strains or genotypes with varying pathogenic potentials. Many strains are pathogenic, but others are avirulent and produce little harm to the host. The availability of methods to assess the pathogenic potential of Aeromonas spp. would contribute to the improved control and prevention strategies for this bacterial infection. An approach to the direct detection of potentially pathogenic Aeromonas spp. is the use of virulence determinants as genetic markers. To investigate the correlation between virulence genes and pathogenicity of Aeromonas spp., 173 strains of Aeromonas were isolated from different diseased freshwater fish from 2009 to 2018 as the research object. Virulence genes including aer, act, fla, lip, gcaT, exu, ast, alt, eprCAI and ahyB were detected and the bacterial pathogenicity with different virulence genotypes was assessed through intraperitoneal (IP) injection challenged Carassius auratus gibelio (gibel carp). Molecular identification revealed that A.veronii (119/173, 68.8%) and A.hydrophila (50/173, 28.9%) were the prevalent species based on gyrB gene sequencing. The distribution of 10 virulence genes including aer (162/173, 93.64%), act (131/173, 75.72%), ast (55/173, 31.79%), alt (58/173, 33.53%), lip (152/173, 87.86%), exu (154/173, 89.02%), fla (143/173, 82.66%), gcaT (148/173, 85.55%), eprCAI(41/173, 23.70%) and ahyB (51/173, 29.48%) were determined and these strains were sorted into 7 clusters (Ⅰ-Ⅶ) and formed 53 genotypes according to the virulence distribution profile. 8-10 virulence genes were present in 24.86% (43/173) Aeromonas strains, among which 38 strains were identified as A. hydrophila and 4 strains A.veronii. The eprCAI (0/119, 0%), ahyB (19/119, 15.13%), ast (7/119, 5.88%) and alt (24/119, 20.17%) genes were detected from the A.veronii isolates. Most of the Aeromonas strains (94.22%, 163/173) had hemolytic activity. At the challenge dose of 3.0×10⁶CFU per fish, 3 strains of A.veronii (Ⅳ-5, Ⅴ-1 and Ⅵ genotype) and 16 strains of A.hydrophila (Ⅰ, Ⅱ-1, Ⅱ-3, Ⅱ-5, Ⅲ-1, Ⅲ-2, Ⅲ-3, Ⅲ-5, Ⅳ-1 and Ⅳ-2 genotype) were highly pathogenic and the mortality reached 80%-100%.The study suggested that A.veronii was the most prevalent species in the diseased fish. A.veronii isolates had fewer virulence genes and lower pathogenicity than A.hydrophila ones. The result may provide reference for epidemiological investigation of motile aeromonad septicemia and vaccine research.

Abstract:Lacustrine goby (Gobiopterus lacustris) belongs to a genus of gobies that are small in size and endemic to freshwater, brackish waters or coastal environments around the Indian and Pacific oceans. G. lacustris has almost transparent skin and clearly visible internal organs, making it an ideal fish model for potential research in development, reproduction and other fields. Here, we constructed gonadal transcriptomes of G. lacustris using Illumina sequencing for the first time and identified genes that may be involved in gonadal development, gametogenesis and reproduction. Row reads were assembled into 62 573 unigenes with N50 value of 3 082 bp and a mean length of 1 869 bp. 41 480, 32 848, 37 500, 35 394, 18 318, 35 394 and 27 009 unigenes were successfully annotated in NR, NT, SwissProt, PFAM, KOG, GO and KEGG databases, respectively. Gene expression patterns in the ovary and testis were compared, and 10 954 differentially expressed genes (DEGs) were identified. Among these genes, 8 571 were up-regulated in the ovary, and 2 383 were up-regulated in the testis. qPCR analysis of 14 selected genes showed patterns consistent with the transcriptome results. Numerous DEGs involved in gonadal development and gametogenesis were identified, including foxl2, dmrt1, cyp19a1a, inha, inhb, sycp2, zglp1, tdrp, zps and esra. Using GO and KEGG enrichment analyses, pathways involved regulation of gonadal development and gametogenesis, such as "ubiquitin mediated proteolysis", "oocyte meiosis", "progesterone-mediated oocyte maturation", "p53 signaling pathway" and "PI3K-Akt signaling pathway", were also identified. In addition, 38 550 simple sequence repeats were identified from 20 517 SSR containing sequences, and 192 450 single nucleotide polymorphisms were detected. This study denotes the first gonadal transcriptomic analysis of G. lacustris and provides a valuable dataset for future functional analysis of sex-associated and molecular marker-assisted selections in G. lacustris.

Abstract:In offshore cage aquaculture, the fouling organisms attached to netting could be detrimental to cage facilities and the living environment of cage-cultured fish. Due to the wide variety of marine fouling organisms, the various changes in the marine environment, the complex structure of net cage, the safety of farmed fish, and the varying conditions of farmers, the anti-fouling work of net cage is very complicated and difficult. Therefore, the antifouling problem of netting has been a cause for concern in offshore cage aquaculture. This paper briefly introduces the classification and the product characteristics of offshore cages; based on these, it then specifies the cutting-edge of offshore cage antifouling technologies, including manual cleaning method, antifouling coating method, mechanical cleaning method, metal alloy netting antifouling method, box rotation antifouling method, biological antifouling method, and the intrinsic antifouling method of netting, etc. Meanwhile, the antifouling effects of these methods, particularly the good and bad effects compared with manual removal method, are summarized. Underpinned by our research group's findings regarding cage antifouling, it analyses the different methods listed above and serves as reference for in-depth study of offshore cage antifouling technologies and green development of offshore cage aquaculture. On the basis of summarizing some cage antifouling methods with their advantages and disadvantages, the authors proposed some research proposals directions for cage antifouling technologies. The first is to study the antifouling mechanism of net coatings and metal alloy net, the intelligent technology of the mechanical cleaning machine and the spinning technology for composite fiber with the intrinsic antifouling function. And the second is to create collaborative anti-fouling technology (such as the combination of mechanical removal method and antifouling coating method or other antifouling methods). In China, there is great potential in offshore cage aquaculture, but there is a long way to go in the study of antifouling technologies of offshore cage netting.

Abstract:The grass carp hemorrhage disease poses a serious threat to the long-term expansion of the aquaculture industry. The barbel chub (Squaliobarbus curriculus) could hybrid with the grass carp to produce progeny possessing resistance to GCRV infection and, therefore, are considered valuable genetic resources for studying the molecular mechanisms of grass carp hemorrhage. To investigate the immune function of barbel chub STAT1 (ScSTAT1) against GCRV infection, the RACE (rapid amplification of cDNA ends), qPCR (quantitative polymerase chain reaction) and RNAi (RNA interference) techniques were applied to obtain the full-length cDNA sequence of ScSTAT1, to detect its expression profile in healthy and GCRV-infected tissues, and to explore its basic immune function. The ScSTAT1 was 2 922 bp in length and encoded a protein of 718 amino acid residues. The ScSTAT1 contained conserved domains for STAT_int, STAT_alpha, STAT_binding and SH2. Phylogenetic analysis revealed that the ScSTAT1 was closely clustered with the homologue from Ctenopharyngodon idella, forming an extended clade with those from Mylopharyngodon piceus, Carassius auratus and Tachysurus fulvidraco. Compared to the homologues from mammals and reptiles, ScSTAT1 lacked a C-terminal TAD domain where a serine phosphorylation site is present. The expression level of ScSTAT1 was shown to be the highest in the spleen among the tissues analyzed, with the lowest level detected in the liver. Treatment of fish with LPS, Poly I:C or GCRV resulted in upregulation of expressions of ScSTAT1 in the spleen and kidney. At 12 h post GCRV infection, the ScSTAT1 expression was down-regulated in the spleen, followed by increases. At 12 h and 72 h post GCRV infection, in trunk kidney the expression levels of ScSTAT1 were significantly higher than those in the control group. In the S. curriculus fin cell (ScF) line, knockdown 60% of ScSTAT1 expression by RNA interference led to decreased expression of IRF3, IRF9 and Mx at 48 h post GCRV infection. The results of the present study proved that ScSTAT1 participated in the signal transduction of the IFN system and played a key role in immune reaction against GCRV infection. The results also provide research basis for further study on the functions of ScSTAT1 in disease resistance in fish.

Abstract:Procambarus clarkii is one of the freshwater lobsters which has important economic value in China. However, long-term high-density farming and inbreeding have brought many negative effects on the cultivation of P. clarkii, such as slow growth, small size, frequent diseases, and the difficulty of artificial breeding caused by the asynchrony of gonadal development, which have severely restricted the further development of P. clarkii aquaculture. In order to find candidate genes involved in ovary development, immunity and muscle growth of P. clarkii for improving the production performance of this species, the transcriptomes of ovary, hepatopancreas and muscle of P. clarkii were sequenced by a new generation of high throughput sequencing technology. After quality control and assembly, the sequences acquired were blasted against NR, Swiss-Prot, pfam, COG, GO and KEGG databases, and then cluster analyses were performed. In total, 53 006 final unigenes with an average length of 1 194 bp were obtained. Pairwise comparison of sequencing libraries of 3 tissue samples revealed that 20 382 differentially expressed genes (DEGs) were found in ovary vs. hepatopancreas group, 12 753 DEGs were found in hepatopancreas vs. muscle group, 21 629 DEGs were found in muscle vs. ovary group. Gene ontology analysis indicated that some DEGs were annotated into "reproduction", "reproduction process", "immune system process" and "growth" GO terms. KEGG pathway analysis showed that some DEGs were enriched in signaling pathways related to ovarian development, immunity and muscle growth. Based on GO functional classification and KEGG pathway analysis, a large number of candidate genes related to ovarian development, immunity and muscle growth of P. clarkii were screened, such as vitellogenin, vitellogenin receptor, Toll-like receptor 2, Toll-interacting protein, myostatin, 5-hydroxytryptamine receptor, etc. The results of this study enriched the gene resources of P. clarkii and could provide basic data for the further genetic breeding and immunity research of this commercial species.