Effect of heat exposure on histology, transcriptomics and co-expression network: A synthetic study in Japanese flounder (Paralichthys olivaceus)

Abstract

Water temperature has continued to increase as part of global warming. The heart of fish is the center that participates in the physiological limitations of thermal performance. However, only a few studies have focused on the response mechanisms of fish hearts to heat stress. Therefore, the economically important cold-water aquaculture fish, Japanese flounder (Paralichthys olivaceus) was chosen to explore the mechanisms of the heart in response to heat stress. Histological observations indicated that heat stress could widen the sarcoplasmic distance and deepen chromatin staining. Further transcriptome analysis identified 958 differentially expressed genes (DEGs), and significantly enriched “Protein processing in endoplasmic reticulum” pathway and related terms in functional enrichment analysis. Weighted gene co-expression network analysis (WGCNA) showed that different tissues had different response modules and hub genes, and calcium ions (Ca2+) related genes and pathways were noteworthy in the heart specific module. Functional identification of key Ca2+ regulatory hub genes illuminated that caveolin-3 (cav3) was an important gene that participates in controlling the Ca2+ into and out of cells. Meanwhile, overexpression of cav3 could reduce heat stress induced apoptosis. This study could not only be a crucial resource for the response mechanisms underlying heat stress in Japanese flounder, but also provide valuable insights into genetic improvement for heat-resistance.