Variation in among-family transcriptional responses to different environmental conditions can help to identify adaptive genetic variation, even prior to a selective event. Coupling differential gene expression with formal survival analyses allows for the disentanglement of treatment effects, required for understanding how individuals plastically respond to environmental stressors, from the adaptive genetic variation responsible for differential survival. We combined these two approaches to investigate responses to an emerging conservation issue, thiamine (vitamin B1 ) deficiency, in a threatened population of Atlantic salmon (Salmo salar). Thiamine is an essential vitamin that is increasingly limited in many ecosystems. In Lake Champlain, Atlantic salmon cannot acquire thiamine in sufficient quantities to support natural reproduction; fertilized eggs must be reared in hatcheries and treated with supplemental thiamine. We evaluated transcriptional responses (via RNA sequencing) to thiamine treatment across families and found 3,616 genes differentially expressed between control (no supplemental thiamine) and treatment individuals. Fewer genes changed expression equally across families (i.e., additively) than exhibited genotype × environment interactions in response to thiamine. Differentially expressed genes were related to known physiological effects of thiamine deficiency, including oxidative stress, cardiovascular irregularities and neurological abnormalities. We also identified 1,446 putatively adaptive genes that were strongly associated with among-family survival in the absence of thiamine treatment, many of which related to neurogenesis and visual perception. Our results highlight the utility of coupling RNA sequencing with formal survival analyses to identify candidate genes that underlie the among-family variation in survival required for an adaptive response to natural selection.

中文翻译：

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生存和基因表达的家庭变异揭示了受威胁鱼类的适应性遗传变异。

即使在选择事件发生之前，家庭之间对不同环境条件的转录反应的变化也可以帮助鉴定适应性遗传变异。将差异基因表达与正式的生存分析相结合，可以使理解个体如何对环境应激源进行塑性反应所需的治疗效果与造成差异生存的适应性遗传变异分离开来。我们结合了这两种方法来研究对濒临灭绝的大西洋鲑（Salmo salar）种群中正在出现的保护问题硫胺素（维生素B1）缺乏的反应。硫胺素是一种必需的维生素，在许多生态系统中日渐受到限制。在尚普兰湖中，大西洋鲑无法获取足够数量的硫胺素来支持自然繁殖。受精卵必须在孵化场饲养，并用硫胺素进行补充处理。我们评估了整个家庭对硫胺素治疗的转录反应（通过RNA测序），发现在对照组（无补充硫胺素）和治疗个体之间有3,616个基因差异表达。与硫胺素反应相比，更少的基因在整个家族中（即加性地）相等地改变了表达，而不是表现出的基因型×环境相互作用。差异表达的基因与硫胺素缺乏的已知生理效应有关，包括氧化应激，心血管异常和神经系统异常。我们还确定了1,446个在没有硫胺素治疗的情况下与家庭间生存密切相关的推定适应性基因，其中许多与神经发生和视觉感知有关。