Institut de Recerca i Tecnologia Agroalimentàries (IRTA)-Institut de Ciències del Mar, CSIC, Barcelona, Spain.
PLoS One. 2013 May 31;8(5):e64410. doi: 10.1371/journal.pone.0064410. Print 2013.
Delayed hatching is a form of dormancy evolved in some amphibian and fish embryos to cope with environmental conditions transiently hostile to the survival of hatchlings or larvae. While diapause and cryptobiosis have been extensively studied in several animals, very little is known concerning the molecular mechanisms involved in the sensing and response of fish embryos to environmental cues. Embryos of the euryhaline killifish Fundulus heteroclitus advance dvelopment when exposed to air but hatching is suspended until flooding with seawater. Here, we investigated how transcriptome regulation underpins this adaptive response by examining changes in gene expression profiles of aerially incubated killifish embryos at ∼100% relative humidity, compared to embryos continuously flooded in water. The results confirm that mid-gastrula embryos are able to stimulate development in response to aerial incubation, which is accompanied by the differential expression of at least 806 distinct genes during a 24 h period. Most of these genes (∼70%) appear to be differentially expressed within 3 h of aerial exposure, suggesting a broad and rapid transcriptomic response. This response seems to include an early sensing phase, which overlaps with a tissue remodeling and activation of embryonic development phase involving many regulatory and metabolic pathways. Interestingly, we found fast (0.5-1 h) transcriptional differences in representatives of classical "stress" proteins, such as some molecular chaperones, members of signalling pathways typically involved in the transduction of sensor signals to stress response genes, and oxidative stress-related proteins, similar to that described in other animals undergoing dormancy, diapause or desiccation. To our knowledge, these data represent the first transcriptional profiling of molecular processes associated with desiccation resistance during delayed hatching in non-mammalian vertebrates. The exceptional transcriptomic plasticity observed in killifish embryos provides an important insight as to how the embryos are able to rapidly adapt to non-lethal desiccation conditions.
延迟孵化是一些两栖动物和鱼类胚胎为应对暂时不利于幼体或幼虫生存的环境条件而进化出的一种休眠形式。虽然滞育和隐生在几种动物中得到了广泛研究，但对于鱼类胚胎感知和响应环境线索的分子机制知之甚少。广盐性的食蚊鱼（Fundulus heteroclitus）胚胎在暴露于空气中时会提前发育，但孵化会暂停，直到被海水淹没。在这里，我们通过比较在相对湿度约为 100%的空气中孵化的胚胎与持续在水中孵化的胚胎，研究了转录组调节如何为这种适应性反应提供基础，从而检查了空气孵化的食蚊鱼胚胎的基因表达谱变化。结果证实，中胚层期胚胎能够在响应空气孵化的情况下刺激发育，在此过程中，至少有 806 个不同的基因在 24 小时内差异表达。这些基因中的大多数（约 70%）似乎在暴露于空气后的 3 小时内差异表达，表明了广泛而迅速的转录组反应。这种反应似乎包括一个早期的感应阶段，与组织重塑和胚胎发育阶段的激活重叠，涉及许多调节和代谢途径。有趣的是，我们发现了经典“应激”蛋白的代表，如一些分子伴侣、通常参与传感器信号向应激反应基因转导的信号通路成员，以及与氧化应激相关的蛋白质，在 0.5-1 小时内就出现了快速（0.5-1 小时）转录差异，这与其他经历休眠、滞育或干燥的动物相似。据我们所知，这些数据代表了在非哺乳动物脊椎动物中延迟孵化期间与抗干燥相关的分子过程的首次转录谱分析。食蚊鱼胚胎表现出的特殊转录组可塑性，为我们了解胚胎如何能够快速适应非致死性干燥条件提供了重要的见解。
