title: Effects of temperature acclimation on Pacific bluefin tuna (Thunnus orientalis) cardiac transcriptome.
abstract: Little is known about the mechanisms underpinning thermal plasticity of vertebrate hearts. Bluefin tuna hearts offer a unique model to investigate processes underlying thermal acclimation. Their hearts, while supporting an endothermic physiology, operate at ambient temperature, and are presented with a thermal challenge when migrating to different thermal regimes. Here, we examined the molecular responses in atrial and ventricular tissues of Pacific bluefin tuna acclimated to 14°C, 20°C, and 25°C. Quantitative PCR studies showed an increase in sarcoplasmic reticulum Ca(2+) ATPase gene expression with cold acclimation and an induction of Na(+)/Ca(2+)-exchanger gene at both cold and warm temperatures. These data provide evidence for thermal plasticity of excitation-contraction coupling gene expression in bluefin tunas and indicate an increased capacity for internal Ca(2+) storage in cardiac myocytes at 14°C. Transcriptomic analysis showed profound changes in cardiac tissues with acclimation. A principal component analysis revealed that temperature effect was greatest on gene expression in warm-acclimated atrium. Overall data showed an increase in cardiac energy metabolism at 14°C, potentially compensating for cold temperature to optimize bluefin tuna performance in colder oceans. In contrast, metabolic enzyme activity and gene expression data suggest a decrease in ATP production at 25°C. Expression of genes involved in protein turnover and molecular chaperones was also decreased at 25°C. Expression of genes involved in oxidative stress response and programmed cell death suggest an increase in oxidative damage and apoptosis at 25°C, particularly in the atrium. These findings provide insights into molecular processes that may characterize cardiac phenotypes at upper thermal limits of teleosts.
authors.affiliation: Stanford University, Hopkins Marine Station, Pacific Grove, California.
authors.forename: Nishad
authors.initials: N
authors.lastname: Jayasundara
authors.forename: Luke D
authors.initials: LD
authors.lastname: Gardner
authors.forename: Barbara A
authors.initials: BA
authors.lastname: Block
mesh_terms: D000064:Acclimatization; D000818:Animals; D017209:Apoptosis / Q000235:genetics; D050260:Carbohydrate Metabolism / Q000235:genetics; D004734:Energy Metabolism / Q000235:genetics; D029941:Fish Proteins / Q000235:genetics* / Q000378:metabolism; D020869:Gene Expression Profiling / Q000379:methods; D005786:Gene Expression Regulation; D050356:Lipid Metabolism / Q000235:genetics; D009206:Myocardium / Q000378:metabolism*; D020411:Oligonucleotide Array Sequence Analysis; D018384:Oxidative Stress / Q000235:genetics; D016133:Polymerase Chain Reaction; D025341:Principal Component Analysis; D019837:Ryanodine Receptor Calcium Release Channel / Q000235:genetics / Q000378:metabolism; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000235:genetics / Q000378:metabolism; D019831:Sodium-Calcium Exchanger / Q000235:genetics / Q000378:metabolism; D013696:Temperature; D014413:Tuna / Q000235:genetics* / Q000378:metabolism
chemical_list: D029941:Fish Proteins; D019837:Ryanodine Receptor Calcium Release Channel; D019831:Sodium-Calcium Exchanger; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases
keywords: bluefin tuna; cardiac function; excitation contraction coupling; temperature acclimation; transcriptomics