Assessing the Pcrit in relation to temperature and the expression of hypoxia associated genes in the mayfly, Neocloeon triangulifer
Assessing the Pcrit in relation to temperature and the expression of hypoxia associated genes in the mayfly, Neocloeon triangulifer
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DOI：
10.1016/j.scitotenv.2021.151743
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发表时间：
2021-12-07
影响因子：
9.8
通讯作者：
Buchwalter, David B.
中科院分区：
文献类型：
--
作者：
Cochran, Jamie K.;Orr, Sarah E.;Buchwalter, David B.
缺氧是水生生态系统中日益受到关注的问题。历史上，科学家们曾使用 P-crit（溶解氧水平低于该水平，动物无法再进行氧调节）来推断物种间的缺氧耐受性。在这里，我们测试了蜉蝣 Neocloeon triangulifer 的 P-crit 与温度正相关的假设。跨温度比较显示温度和 P-crit 之间存在适度 (r = 0.47) 但显着 (p < 0.0001) 的关联，尽管个体间差异相对较大（18 摄氏度时方差系数 (CV) = 39.9%）。我们使用缺氧反应基因 EGL-9（氧传感基因和 HIF-1a 活性调节剂）和 LDH（缺氧指标）的表达来测试 P-crit 附近的氧分压是否刺激缺氧反应基因的表达。当氧气水平高于估计的 P-crit 时，这两个基因都没有上调，然而，在等于或低于 P-crit 估计值时，这两个基因的表达都受到刺激（分别类似于 EGL-9 和 IDH 的 20 倍和 3 倍变化）。最后，我们评估了低氧暴露时间和预处理条件对低氧反应基因 mRNA 表达水平的影响。当幼虫暴露于逐渐减少的溶解氧时，缺氧基因的表达比瞬时暴露于缺氧时更加强烈。我们的数据为 P-crit 的传统解释提供了适度的支持，P-crit 是三角猪笼草从有氧代谢到无氧代谢的生理上有意义的转变。然而，我们还讨论了 P-crit 作为物种水平缺氧耐受性替代指标的局限性。
Hypoxia is a growing concern in aquatic ecosystems. Historically, scientists have used the P-crit (the dissolved oxygen level below which an animal can no longer oxyregulate) to infer hypoxia tolerance across species. Here, we tested the hypothesis that the P-crit is positively correlated with temperature in the mayfly, Neocloeon triangulifer. Cross-temperature comparisons showed a modest (r = 0.47), but significant (p < 0.0001) association between temperature and P-crit despite relatively large interindividual variability (Coefficient of Variance (CV) = 39.9% at 18 degrees C). We used the expression of hypoxia-responsive genes EGL-9 (an oxygen sensing gene and modulator of HIF-1a activity) and LDH (a hypoxia indicator) to test whether oxygen partial pressure near the P-crit stimulates expression of hypoxia-responsive genes. Neither gene was upregulated at oxygen levels above the estimated P-crit however, at or below the P-crit estimates, expression of both genes was stimulated (similar to 20- and similar to 3-fold change for EGL-9 and IDH, respectively). Finally, we evaluated the influence of hypoxic exposure time and pretreatment conditions on the mRNA expression levels of hypoxia-responsive genes. When larvae were exposed to a gradual reduction of DO, hypoxic gene expression was more robust than during instantaneous exposure to hypoxia. Our data provide modest support for traditional interpretation of the P-crit as a physiologically meaningful shift from aerobic to anaerobic metabolism in N. triangulifer. However, we also discuss limitations of the P-crit as a proxy measure of hypoxia tolerance at the species level.