Acute temperature stresses trigger liver transcriptome and microbial community remodeling in largemouth bass (Micropterus salmoides)

Abstract

The largemouth bass is an important freshwater fish in China. As global climate changes, mass mortality in largemouth bass due to extremely low/high temperatures has aroused growing concern. In the present study, we investigated the physiological responses of the liver and intestine in largemouth bass to acute low/high-temperature stresses. Acute low/high-temperature stresses caused histological alterations such as structural damage in the liver. Based on liver transcriptomic data, a total of 6678 differentially expressed genes (DEGs) were detected, of which 2106, 5235, 3 and 449 DEGs were identified in fish treated with temperatures of 9 °C (serve cold-stress group, SC group), 18 °C (light cold-stress group, LC group), 30 °C (light heat-stress group, LH group), and 33 °C (serve heat-stress group, SH group), respectively. Further functional analysis found that the apoptosis, amino acid metabolism and lipid metabolism related signaling pathways were significantly enriched in fish after low-temperature stress, and protein processing in endoplasmic reticulum were significantly associated with heat stress. The weighted gene co-expression network analysis (WGCNA) results showed that multiple modules were significantly correlated with the LC or SC or SH groups, in which key signaling pathways were identified. Meanwhile, sequencing of the bacterial 16S rDNA gene demonstrated that acute high temperature stress reshaped the composition of the microbial community. Correlation analysis between bacteria and DEGs showed that bacteria could regulate pathways to affect the healthy status of host. This study provides the first systematic analysis about the adaptative responses of largemouth bass under acute temperature stresses by unveiling microbial, transcriptional, and histological changes, and identify microbial biomarkers/genes to monitor the health status of largemouth bass and to improve fish temperature tolerance, which will lay the foundation for further studies on the environmental stress response in largemouth bass.