Gill histological and transcriptomic analysis provides insights into the response of spotted sea bass (Lateolabrax maculatus) to alkalinity stress

Abstract

Spotted sea bass (Lateolabrax maculatus), possessing a superior adaptation ability to a wide range of salinities, is a valuable candidate to develop saline-alkaline tolerant fish strains in China, and therefore exploring the mechanism of response to alkalinity environment is necessary to accelerate the molecular breeding program. In this study, gill morphological and transcriptomic profiles of spotted sea bass was characterized after alkalinity stress. Several morphological parameters of gill tissues were measured and quantified, showing the significantly histological changes after alkalinity challenge. RNA-Seq analysis identified a total of 2141 differentially expressed genes (DEGs) upon alkalinity exposure. Based on the soft clustering analysis, KEGG enrichment analysis and Gene Set Enrichment Analysis (GSEA), the up-regulated DEGs were significantly associated with cell-cell junctions and cell-ECM interactions (such as “ECM-receptor interaction”, “Focal adhesion” and “Cell adhesion molecules”), signal transduction (including “Apelin signaling pathway”, “MAPK signaling pathway”, and “Hedgehog signaling pathway”), as well as ion transportation. Protein-Protein Interaction (PPI) analysis revealed that 13 genes including col6a1, itga9, itgb1, itgb4, pik3r2, ctnna2, kdrl, col6a1, fgf2, met, ptk2, itga8, and cdh2 were identified as hub genes. The down-regulated DEGs were significantly enriched in genetic information processing related categories, including “Cell cycle”, “RNA polymerase”, “RNA transport”, “Spliceosome”, “Ribosome”, “Protein process in endoplasmic reticulum” and “Protein export”. Among them, 11 genes including jun, gapdh, fos, atf3, cebpb, egr1, aurka, aurkb, cdc20, mad2l1, and ccnb1 were recognized as hub genes. Additionally, totally 549 alkalinity-induced differential alternative splicing (DAS) genes were characterized, most of which belonged to skipped exon type and enriched in metabolic pathways and cell-cell junctions associated functional sets. Our study provides insights into the genetic basis for alkalinity adaptation, and will facilitate to select the regulatory elements potential applied for molecular breeding programs for the utilization of alkalinity waters.