Visceral white nodules disease (VWND), caused by Pseudomonas plecoglossicida, is a common disease among cage-farmed large yellow croaker (Larimichthys crocea) in China. However, comprehensive investigations of the molecular defensive mechanisms used by L. crocea in response to P. plecoglossicida infection remain relatively rare. Here, we constructed transcriptomes of the L. crocea spleen at 12 h and 24 h after P. plecoglossicida challenge. We identified 518 novel miRNAs and 823 known miRNAs in the spleen of L. crocea. Between the challenge and control groups, 32 differentially expressed miRNAs (DEmiRNAs), predicted to target 356 genes, and 1152 differentially expressed mRNAs (DEmRNAs) were identified at 12 h post-infection, while 33 DEmiRNAs, predicted to target 278 genes, and 1067 DEmRNAs were identified at 24 h post-infection. Gene ontology (GO) analysis showed that 146 and 126 GO terms were significantly enriched in the target genes at 12 h and 24 h, respectively. Twenty-eight and four immune-associated Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways were significantly enriched in the target genes at 12 h and 24 h, respectively. Three immune-associated pathways were among those most enriched in the target genes: Toll-like receptor signaling, endocytosis, and C-type lectin receptor signaling. Network analysis identified 47 DEmRNA-DEmiRNA pairs. In particular, the immune-related genes TLR5S and PIGR were targeted by the miRNAs lcr-miR-7132c and dre-miR-183-5p, respectively. Dual-luciferase assays verified that lcr-miR-7132c downregulated TLR5S, suggesting that this miRNA may participate in regulating the immune response of L. crocea to P. plecoglossicida infection through the TLR5S-mediated signaling pathway. Our results help to clarify the miRNA-mediated immune response of L. crocea to P. plecoglossicida infection.

Silurus lanzhouensis is a large endemic fish exclusively found in the middle and upper reaches of China’s Yellow River, with a restricted distribution range and a small population size and is listed as an endangered species. To investigate the potential genetic factors contributing to the observed decrease in the population of S. lanzhouensis, we have successfully assembled the first chromosome-level genome of S. lanzhouensis. This genome comprises a total of 30 chromosomes, with a size of 794.43 Mb, and 23,093 protein-coding genes. Comparative genomics analysis reveals that the genetic relationship between S. lanzhouensis and S. meridionalis Chen is the closest, and their common ancestor experienced two rounds of whole genome duplication (WGD) before diverging. Notably, amino acid metabolism-related pathways are enriched in the unique S. lanzhouensis gene family. In addition, we observed that the chemokine receptor and scavenger receptor gene families contracted in S. lanzhouensis, which may be associated with its diminished immune response. Our research findings provide valuable insights into the endangered mechanism of S. lanzhouensis and enhance our understanding of the evolution of Siluriformes fish.