Catfish farming accounts for ~70% of total U.S. freshwater aquaculture production, where the channel catfish, Ictalurus punctatus ? × blue catfish I. furcatus ? hybrid constitutes >50% of the harvest. Current technologies to produce hybrid embryos are labor intensive and require the sacrifice of males that do not reach maturity for 4-7 years. Catfish sperm are then often of inadequate quality/quantity and do not necessarily yield high fertility. Thus, our objectives were to i) identify miRNA in testes and sperm; ii) compare differential expression of testes sRNA between males; iii) decipher differences in sRNA from testes and sperm; iv) describe relevant biological pathways for mapped miRNA; and v) describe sequence length differences in sRNA between tissue types.
Five mature blue catfish males (2.67 ± 0.72 kg) were harvested from aquaculture ponds. Testes and sperm were then snap frozen for molecular analyses. Samples were shipped to Novogene Corporation for sequencing and bioinformatic analysis using I. punctatus (v. IpCoco_1.2) as the reference genome.
There were 174 known mature miRNAs detected. All known miRNAs from sperm samples were also detected in testes samples, and 5 novel miRNAs were unique to sperm samples. sRNAs with differential expression were clustered using DESeq2, revealing that testes and sperm show different expression patterns (Fig. 1). KEGG enrichment showed that detected miRNAs were primarily devoted to metabolism and endocytosis. Sperm samples peaked at 33 nucleotides (nt) displaying more piRNA, whereas testes peaked at 22 nt, displaying more miRNA. Overall, this study describes the small RNA profiles in I. furcatus male gonadal tissue and gametes, including core miRNAs that should be further characterized as biomarkers.