Landscapes of alternative splicing genes/events in the gills of Mozambique tilapia (Oreochromis mossambicus) and their roles in high-salinity adaptation

Abstract

Salinity could directly influence the survival and physiological conditions of fishes. Because of its importance, the salinity adaptation and osmoregulation mechanism have been extensively studied in the last decade. However, the adaptation to high-salinity environments has yet to be explored, particularly at the post-transcriptional level. In the present study, 18 RNA-seq datasets were utilized to investigate the alternative splicing (AS) events of functional genes in the gills of Mozambique tilapia (Oreochromis mossambicus) exposed to different salinity environments ranging from 0‰ (T0) to 110‰ (T110). A total of 1266 ~ 3194 differential alternative splicing (DAS) events were identified in 5 pairwise comparisons (T30 vs. T0, T50 vs. T0, T70 vs. T0, T90 vs. T0, and T110 vs. T0). It was derived from 971 to 2080 functional genes that were defined as DAS genes. Enrichment analysis indicated that these DAS genes in 5 comparison groups were commonly enriched in the spliceosome pathway. In detail, 31 spliceosome-associated genes were tightly related to spliceosome assembly, RNA binding, and RNA splicing. DAS events of these spliceosome-associated genes would alter the splicing decisions of downstream target genes. Differential expression analysis, together with protein interaction networks, was performed to determine their target genes. Functional categorization revealed that these target genes were mainly involved in energy metabolism in the mitochondrion, protein synthesis in the ribosome, and signal transduction in the cytoplasm, which may be responsible for the high-salinity adaptation in the gills of Mozambique tilapia. This study provides novel insights into the post-transcriptional regulation mechanisms underlying high-salinity adaptation in fishes.