Thermal adaptation affects expression and regulation of metabolism-, stress-, and immune-related genes in Artemia franciscana populations

Brine shrimp Artemia franciscana is a commercially important species in aquaculture and is well adapted to harsh environmental conditions. In this study, an A. franciscana population selectively bred for induced thermotolerance over 12 generations (TF12) was subjected to transcriptomic analysis relative to the non-selective population (CF12) to determine the effect of selective breeding for induced thermotolerance (SITT). The transcriptomic response of CF12 to non-lethal heat stress (NLHS) from induced thermotolerance (ITT) within one generation was also investigated. A total of 232 and 218 differentially expressed genes (DEGs) were upregulated and downregulated in TF12, respectively, whereas fewer DEGs were upregulated (114) and downregulated (180) in CF12 exposed to NLHS, suggesting a more complex mechanism of thermal adaptation in SITT than in ITT. The TF12 population exhibited a reduction in immune processes as indicated by the downregulation of several pattern-recognition receptors. Conversely, stress protein genes such as those of heat shock proteins (HSPs) and of antioxidant enzymes and genes involved in carbohydrate metabolism, were highly upregulated. ITT downregulated immune-related and growth-related genes, whereas genes involved in energy production and electron carrier activity were upregulated. Our findings suggest possible immunological and physiological mechanisms and molecular pathways involved in adaptation of A. franciscana to thermal stress.