ABSTRACT
Fish egg poisoning is a serious and neglected public menace that kills hundreds of people and numerous poultry each year. Freshwater groupers (Acrossocheilus fasciatus) are common food fish in the southeastern regions of China. Their toxic eggs are regarded as a significant public health concern. The molecular mechanisms of egg-toxin toxicity in freshwater grouper to poisoned organisms are elusive. In this study, black-boned chicks were exposed to toxic eggs from freshwater grouper at a lethal dose. The hepatic morphology of the intoxicated chick was assessed. An analysis of the liver gene expression profile was conducted by comparing samples exposed to toxic eggs with control samples using RNA-Seq. The result revealed that an increase in vacuolation and congestion was observed in chicks with toxic eggs exposure. The transcriptome analysis revealed 5421 genes with differential expression, comprising 2810 up-regulated and 2611 down-regulated genes. The genes were primarily linked to energy metabolism, cell apoptosis, cell adhesion, exogenous microbial infection, and cell junction. The most strongly upregulated genes were cholecystokinin (CCK), cholecystokinin A receptor (CCKAR), and unc-80 homolog, NALCN activator (UNC80), and the most downregulated genes were glycine amidinotransferase (GATM), fatty acid desaturase 2 (FADS2), and hexokinase 2 (HKDC1). GO term with the highest enrichment of DEGs is nucleosome assembly. According to KEGG pathways, the three most significant metabolic pathways in the liver are DNA replication, retinol metabolism, and steroid biosynthesis. The results could be crucial for comprehending the negative biological impacts of egg-toxin and its toxic mechanisms. The outcome could provide potential biomarkers of egg-toxin exposure in hepatic, which might be useful for manufacturing an antidote to egg-toxin and providing valuable insights for ecotoxicity studies.
ABSTRACT
Acrossocheilus fasciatus is a stream-dwelling fish species of the Barbinae subfamily. It is valued for its colorfully striped appearance and delicious meat. This species is also characterized by apparent sexual dimorphism and toxic ovum. Biology and aquaculture researches of A. fasciatus are hindered by the lack of a high-quality reference genome. Here, we report chromosome-level genome assemblies of the male and female A. fasciatus. The HiFi-only genome assemblies for both female and male individuals were 899.13 Mb (N50 length of 32.58 Mb) and 885.68 Mb (N50 length of 33.06 Mb), respectively. Notably, a substantial proportion of the assembled sequences, accounting for 96.15% and 98.35% for female and male genomes, respectively, were successfully anchored onto 25 chromosomes utilizing Hi-C data. We annotated the female assembly as a reference genome and identified a total of 400.62 Mb (44.56%) repetitive sequences, 27,392 protein-coding genes, and 35,869 ncRNAs. The high-quality male and female reference genomes will provide genomic resources for developing sex-specific molecular markers, inform single-sex breeding, and elucidate genetic mechanisms of sexual dimorphism.
