Department of Forest and Conservation Sciences, University of British Columbia, Vancouver, BC, Canada, V6T 1Z4.
Pacific Biological Station, Fisheries and Oceans Canada, Nanaimo, BC, Canada, V9T 6N7.
J Exp Biol. 2019 Jul 5;222(Pt 13):jeb198036. doi: 10.1242/jeb.198036.
An organism's ability to respond effectively to environmental change is critical to its survival. Yet, life stage and overall condition can dictate tolerance thresholds to heightened environmental stressors, such that stress may not be equally felt across individuals and at all times. Also, the transcriptional responses induced by environmental changes can reflect both generalized responses as well as others that are highly specific to the type of change being experienced. Thus, if transcriptional biomarkers specific to a stressor, even under multi-stressor conditions, can be identified, the biomarkers could then be applied in natural environments to determine when and where an individual experiences such a stressor. Here, we experimentally challenged juvenile Chinook salmon () to validate candidate gill gene expression biomarkers. A sophisticated experimental design manipulated salinity (freshwater, brackish water and seawater), temperature (10, 14 and 18°C) and dissolved oxygen (normoxia and hypoxia) in all 18 possible combinations for 6 days using separate trials for three smolt statuses (pre-smolt, smolt and de-smolt). In addition, changes in juvenile behaviour, plasma variables, gill Na/K-ATPase activity, body size, body morphology and skin pigmentation supplemented the gene expression responses. We identified biomarkers specific to salinity and temperature that transcended the multiple stressors, smolt status and mortality (live, dead and moribund). Similar biomarkers for dissolved oxygen were not identified. This work demonstrates the unique power of gene expression biomarkers to identify a specific stressor even under multi-stressor conditions, and we discuss our next steps for hypoxia biomarkers using an RNA-seq study.
生物体有效应对环境变化的能力对其生存至关重要。然而，生命阶段和整体状况可以决定其对环境胁迫的耐受阈值，因此，压力在个体之间和不同时间可能并不均等感受到。此外，环境变化引起的转录反应既可以反映普遍反应，也可以反映对所经历的变化类型高度特异的反应。因此，如果可以识别出特定于胁迫的转录生物标志物，即使在多胁迫条件下，这些生物标志物也可以应用于自然环境中，以确定个体何时何地经历这种胁迫。在这里，我们通过实验挑战幼年奇努克鲑鱼（Oncorhynchus tshawytscha），以验证候选鳃基因表达生物标志物。一个复杂的实验设计通过使用单独的试验，操纵了盐度（淡水、半咸水和海水）、温度（10、14 和 18°C）和溶解氧（常氧和缺氧）在所有 18 种可能的组合中，持续 6 天，针对三种洄游状态（预洄游、洄游和离游）。此外，青少年行为、血浆变量、鳃 Na/K-ATP 酶活性、体型、身体形态和皮肤色素沉着的变化补充了基因表达反应。我们确定了特定于盐度和温度的生物标志物，这些生物标志物超越了多种胁迫、洄游状态和死亡率（存活、死亡和濒死）。没有确定特定于溶解氧的类似生物标志物。这项工作证明了基因表达生物标志物在多胁迫条件下识别特定胁迫的独特能力，我们讨论了使用 RNA-seq 研究确定缺氧生物标志物的下一步措施。
