Data from: Loggerhead sea turtle embryos (Caretta caretta) regulate expression of stress-response and developmental genes when exposed to a biologically realistic heat stress

Oviparous reptile embryos are expected to breach their critical thermal maxima if temperatures reach those predicted under current climate change models due to the lack the maternal buffering processes and parental care. Heat shock proteins (HSPs) are integral in the molecular response to thermal stress, and their expression is heritable, but the roles of other candidate families such as the heat shock factors (HSFs) have not been determined in reptiles. Here we subject embryonic sea turtles (Caretta caretta) to a biologically realistic thermal stress and employ de novo transcriptomic profiling of brain tissue to investigate the underlying molecular response. From a reference transcriptome of 302,293 transcripts, 179 were identified as differentially expressed between treatments. As anticipated, genes enriched in the heat shock treatment were primarily associated with the Hsp families, or were genes whose products play similar protein editing and chaperone functions (e.g. bag3, MYOC and serpinh1). Unexpectedly, genes encoding the HSFs were not significantly upregulated under thermal stress, indicating their presence in unstressed cells in an inactive state. Genes that were downregulated under thermal stress were less well functionally defined but were associated with stress response, development, and cellular organization, suggesting that developmental processes may be compromised at realistically high temperatures. These results confirm that genes from the Hsp families play vital roles in the thermal tolerance of developing reptile embryos, and in addition with a number of other genes, should be targets for evaluating the capacity of oviparous reptiles to respond adaptively to the effects of climate change.

鉴于缺乏母体缓冲过程与双亲抚育行为，若气温达到当前气候变化模型所预测的水平，卵生爬行动物胚胎将突破其临界热最大值（critical thermal maxima）。热休克蛋白（heat shock proteins, HSPs）是热应激分子响应的核心组分，其表达具有可遗传性，但包括热休克因子（heat shock factors, HSFs）在内的其他候选基因家族在爬行动物中的作用尚未明确。本研究将绿海龟（Caretta caretta）胚胎暴露于符合生物学现实情境的热应激环境中，并通过对脑组织开展从头转录组测序（de novo transcriptomic profiling）以探究其潜在的分子响应机制。在由302293条转录本构建的参考转录组中，共鉴定出179个不同处理组间的差异表达基因。正如预期，热应激处理组中富集的基因主要隶属于热休克蛋白家族，或编码具有相似蛋白质编辑与分子伴侣功能的蛋白产物（如bag3、MYOC及serpinh1）。出乎意料的是，编码热休克因子的基因在热应激条件下并未出现显著上调，这表明它们在未受应激的细胞中以非激活状态存在。热应激下下调的基因功能注释尚不充分，但均与应激响应、发育及细胞组织构建相关，这提示在符合现实情境的高温环境中，胚胎的发育过程可能受到损害。本研究结果证实，热休克蛋白家族基因在发育中爬行动物胚胎的热耐受性中发挥关键作用；此外，连同其他若干基因，这些靶点可用于评估卵生爬行动物对气候变化影响做出适应性响应的能力。