The Good, the Bad, and the Lethal: Gene Expression and Metabolomics Reveal Physiological Mechanisms Underlying Chronic Thermal Effects in Mayfly Larvae (Neocloeon triangulifer)
The Good, the Bad, and the Lethal: Gene Expression and Metabolomics Reveal Physiological Mechanisms Underlying Chronic Thermal Effects in Mayfly Larvae (Neocloeon triangulifer)
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DOI：
10.3389/fevo.2018.00027
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发表时间：
2018-03-23
影响因子：
3
通讯作者：
Buchwalter, David B.
中科院分区：
文献类型：
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作者：
Chou, Hsuan;Pathmasiri, Wimal;Buchwalter, David B.
温度决定了水生变温动物的行为。然而，驱动热介导的生活史模式（和限制）的生理和生化过程仍然知之甚少，因为它们很少同时研究。在我们之前的工作中，我们已经建立了在14至30摄氏度的静态温度下以2摄氏度的间隔饲养的蜉蝣（新三角蜉蝣）的生活史结果（例如存活率、发育时间、生长速度和适应性）。在这项研究中，我们对三角鳗成熟幼虫进行了生化测量（选择基因的RT-qPCR和有针对性的定量代谢组学分析），这些幼虫在良好的生存和适合度（22-24℃）下饲养，在生存和适合度（28℃）下饲养，在慢性致死率（30℃）下饲养，幼虫存活了几周，但未能成虫。基因表达模式与之前报道的急性生长实验相似：在30℃下饲养的幼虫导致热反应基因热休克蛋白90 （HSP90）显著上调，但缺氧反应基因[产蛋缺陷9 （EGL-9）和乳酸脱氢酶（LDH）]没有显著变化。此外，本研究还开发了与能量相关基因的引物：胰岛素受体（IR）、雷帕霉素的机械靶（mTOR）和海藻糖6磷酸合成酶（T6PS）。在30℃条件下，IR和m - TOR显著上调，而T6PS呈下调趋势，代谢组学分析显示，慢性热应激下的幼虫脂质和酰基肉碱普遍耗竭，表明尽管持续获取食物，但幼虫仍受到能量挑战。例如，溶血磷脂酰胆碱（lysoPC） a C20:3的浓度随着温度的升高而降低（在28℃和30℃时是对照的2.3倍和2.4倍）。生物胺组胺组织浓度随温度升高分别升高2.1倍和3.1倍，且与生产性能呈显著负相关。因此，组胺和lysoPC a C20:3都是热应激的潜在生物标志物。综上所述，我们的研究结果主要将能量挑战与三角鳉鱼热介导的适应性降低联系起来。
Temperature dictates the performance of aquatic ectotherms. However, the physiological and biochemical processes that drive thermally-mediated life history patterns (and limits) remain poorly understood because they are rarely studied simultaneously. In our previous work, we have established life history outcomes (e.g., survivorship, development time, growth rates, and fitness) in mayflies (Neocloeon triangulifer) reared at static temperatures ranging from 14 to 30 degrees C at 2 degrees C intervals. In this study, we conducted biochemical measurements (RT-qPCR of select genes and targeted, quantitative metabolomic profiling) on N. triangulifer mature larvae reared at temperatures associated with excellent survival and fitness (22-24 degrees C) compromised survival and fitness (28 degrees C), and chronic lethality (30 degrees C-larvae survived for a few weeks but failed to emerge to adulthood). Patterns of gene expression were similar to those observed in acute ramping experiments reported previously: larvae reared at 30 degrees C resulted in significant upregulation in the thermally responsive gene HEAT SHOCK PROTEIN 90 (HSP90) but no significant changes in hypoxia responsive genes [EGG LAYING DEFECTIVE 9 (EGL-9) and LACTATE DEHYDROGENASE (LDH)]. Additionally, primers for genes associated with energy: INSULIN RECEPTOR (IR), mechanistic TARGET OF RAPAMYCIN (mTOR), and TREHALOSE 6 PHOSPHATE SYNTHASE (T6PS) were developed for this study. IR and m TOR were significantly upregulated while T6PS showed trend of downregulation in larvae reared at 30 degrees C. Metabolomic profiles revealed general depletion of lipids and acylcarnitines in larvae exposed to chronic thermal stress, suggesting that larvae were energetically challenged despite continuous access to food. For example, concentrations of lysoPhosphatidylcholine (lysoPC) a C20:3 decreased as fitness decreased with increasing temperature (2.3- and 2.4-fold at 28 and 30 degrees C relative to controls). Tissue concentrations of the biogenic amine histamine increased 2.1- and 3.1-fold with increasing temperature, and were strongly and negatively correlated with performance. Thus, both histamine and lysoPC a C20:3 are potential biomarkers of thermal stress. Taken together, our results primarily associate energetic challenge with thermally mediated fitness reduction in N. triangulifer.