Cathepsin H and cathepsin B of Cynoglossus semilaevis are involved in anti-bacterial immunity against Edwardsiella tarda

Functional insights of digestion, absorption, and immunity in different segments of the intestine in Hemibarbus labeo from transcriptomic analysis

The intestine is an important organ for food digestion and absorption and body immunity in fish. In this study, we investigated the abundance of transcripts from different segments of the intestinal tract using transcriptome sequencing technology in Hemibarbus labeo, to provide functional insights into digestion, absorption, and immunity in the anterior intestine (AI), middle intestine (MI), and posterior intestine (PI). We found 5646 differentially expressed genes (DEGs), which were significantly enriched to GO terms of carbohydrate metabolic process, transmembrane transport, iron ion binding, lipid metabolic process, and KEGG pathway of fat digestion and absorption, mineral absorption, protein digestion and absorption, vitamin digestion and absorption, indicating that the digestion and absorption function of food is different in AI, MI, and PI. In practice, most genes, enriched in the KEGG pathway for digestion and absorption of nutrients, are upregulated in AI and MI, indicating stronger roles for food digestion and absorption in these segments. Furthermore, we found that genes involved in the KEGG pathway of lysosome and endocytosis pathway are upregulated in PI, suggesting stronger antigen-presenting capabilities in PI. However, some cytokine receptor genes, including ccr4, cxcr2, tnfrsf9, il6r, csf3r, and cxcr4, are highly expressed in AI, reflecting the regional immune specialization in different segments. This study provides functional insights into digestion, absorption, and immunity in different segments of the intestine and supports the regional functional specialization within different segments of the intestine in H. labeo.

Conventional Anthelmintic Concentration of Deltamethrin Immersion Disorder in the Gill Immune Responses of Crucian Carp

Current treatment strategies for parasitic infectious diseases in crucian carp primarily rely on chemotherapy. As a commonly used antiparasitic agent, deltamethrin (DEL) may have the potential adverse effects on external mucosa of fish such as gills. In this study, 180 healthy juvenile crucian carp (Carassius auratus) (average weight: 8.8 ± 1.0 g) were randomly divided into three groups for 28 days, which were immersed in 0 μg/L, 0.3 μg/L, and 0.6 μg/L of DEL, respectively. The results of histological analysis revealed that severe hyperplasia in the secondary lamellae of gills was observed, and the number of goblet (mucus-secreting) cells increased significantly after DEL immersion. TUNEL staining indicated that the number of apoptotic cells increased in crucian carp gill. At the molecular level, the mRNA expression analysis revealed significant upregulation of apoptosis (caspase 3, caspase 8, and bax), autophagy (atg5 and beclin-1), and immune response (lzm, muc5, il-6, il-8, il-10, tnfα, ifnγ, tgfβ, tlr4, myd88, and nf-kb), whereas tight junction-related genes (occludin and claudin12) were downregulated after DEL immersion, suggesting that DEL immersion altered innate immunity responses and promoted mucus secretion. Moreover, tandem mass tag (TMT)-based proteomics revealed that a total of 428 differentially expressed proteins (DEPs) contained 341 upregulated DEPs and 87 downregulated DEPs with function annotation were identified between the control and DEL groups. Functional analyses revealed that the DEPs were enriched in apoptotic process, phagosome, and lysosome pathways. Additionally, DEL immersion also drove gill microbiota to dysbiosis and an increase in potentially harmful bacteria such as Flavobacterium. Overall, this study showed that DEL elicited shifts in the immune response and changes in the surface microbiota of fish. These results provide new perspectives on the conventional anthelmintic concentration of DEL immersion disorder of the gill immune microenvironment in crucian carp and theoretical support for future optimization of their practical application.

Transcriptome analysis of response mechanism to Microcystin-LR and microplastics stress in Asian clam (Corbicula fluminea)

In this study, we analyzed the hepatopancreas tissues of Asian Clam (Corbicula fluminea) exposed to three different adverse environmental conditions from the same batch using RNA-seq. The four treatment groups included the Asian Clam group treated with Microcystin-LR (MC), the Microplastics-treated group (MP), the Microcystin-LR and Microplastics-treated group (MP-MC), and the Control group. Our Gene Ontology analysis revealed 19,173 enriched genes, and the Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis identified 345 related pathways. The KEGG pathway analysis demonstrated that the MC vs control group and the MP vs control group were significantly enriched in immune and catabolic pathways such as Antigen processing and presentation, Rheumatoid arthritis, Lysosome pathway, Phagosome pathway, and Autophagy pathway. We also evaluated the effects of Microplastics and Microcystin-LR on the activities of eight antioxidant enzymes and immune enzymes in Asian clams. Our study enriched the genetic resources of Asian clams and provided valuable information for understanding the response mechanism of Asian clams to microplastics and microcystin in the environment, through the identification of differentially expressed genes and related pathway analyses from the large number of transcriptome sequences obtained.