Department of Biology, University of Regina, 3737 Wascana Parkway, Regina, SK, S4S 0A2, Canada.
Medical Sciences, Northern Ontario School of Medicine, Laurentian University, Sudbury, ON, P3E 2C6, Canada.
J Therm Biol. 2021 Aug;100:103036. doi: 10.1016/j.jtherbio.2021.103036. Epub 2021 Jun 26.
We examined the impact of repeated thermal stress on the heat shock response (HSR) of thermally sensitive lake whitefish (Coregonus clupeaformis) embryos. Our treatments were designed to mimic temperature fluctuations in the vicinity of industrial thermal effluents. Embryos were either maintained at control temperatures (3 C) or exposed to a repeated thermal stress (TS) of 3 or 6 C above control temperature every 3 or 6 days throughout embryonic development. At 82 days post-fertilisation, repeated TS treatments were stopped and embryos received either a high level TS of 12, 15, or 18 C above ambient temperature for 1 or 4 h, or no additional TS. These treatments were carried out after a 6 h recovery from the last repeated TS. Embryos in the no repeated TS group responded, as expected, with increases in hsp70 mRNA in response to 12, 15 and 18 C high-level TS. However, exposure to repeated TS of 3 or 6 ⁰C every 6 days also resulted in a significant upregulation of hsp70 mRNA relative to the controls. Importantly, these repeated TS events and the associated elevations in hsp70 attenuated the upregulation of hsp70 in response to a 1 h, high-level TS of 12 C above ambient, but not to either longer (4 h) or higher (15 or 18 C) TS events. Conversely, hsp90α mRNA levels were not consistently elevated in the no repeated TS groups exposed to high-level TS. In some instances, hsp90α levels appeared to decrease in embryos exposed to repeated TS followed by a high-level TS. The observed attenuation of the HSR in lake whitefish embryos demonstrates that embryos of this species have plasticity in their HSR and repeated TS may protect against high-level TS, but the response differs based on repeated TS treatment, high-level TS temperature and duration, and the gene of interest.
我们研究了重复热应激对热敏湖白鲑（Coregonus clupeaformis）胚胎热休克反应（HSR）的影响。我们的处理旨在模拟工业热废水附近的温度波动。胚胎要么保持在对照温度（3°C）下，要么在胚胎发育过程中每 3 或 6 天暴露于对照温度以上 3 或 6°C 的重复热应激（TS）下。在受精后 82 天，重复 TS 处理停止，胚胎接受 12、15 或 18°C 的高水平 TS，持续 1 或 4 小时，或不接受额外的 TS。这些处理是在最后一次重复 TS 后 6 小时恢复后进行的。在没有重复 TS 的组中，如预期的那样，hsp70 mRNA 对 12、15 和 18°C 的高水平 TS 反应增加。然而，暴露于每 6 天 3 或 6°C 的重复 TS 也导致 hsp70 mRNA 的显著上调，相对于对照。重要的是，这些重复的 TS 事件和相关的 hsp70 升高减弱了对 12°C 以上高水平 TS 的 1 小时持续时间的 HSR 的上调，但对较长（4 小时）或更高（15 或 18°C）的 TS 事件没有影响。相反，在暴露于高水平 TS 的无重复 TS 组中，hsp90α mRNA 水平没有一致升高。在某些情况下，在暴露于重复 TS 后，hsp90α 水平似乎在暴露于高水平 TS 的胚胎中降低。湖白鲑胚胎 HSR 的这种衰减表明，该物种的胚胎在其 HSR 中具有可塑性，重复 TS 可能对高水平 TS 具有保护作用，但反应因重复 TS 处理、高水平 TS 温度和持续时间以及感兴趣的基因而异。
