The physiological and genomic basis to the timing of life history transitions in the Atlantic salmon

在洄游性大西洋鲑鱼中，在淡水溪流中出生的幼鱼（幼鱼）变成洄游性“小鲑鱼”并出海的过程代表了一个关键的生命史转变，涉及复杂的行为和生理变化。其中最神秘的是获得嗅觉'印记'的纳塔尔流，在小鲑鱼迁移之前，在成年后返回取决于。同样的，对于控制春季小鲑鱼向幼鱼转变的神经和神经内分泌事件也知之甚少。因此，小鲑鱼表型的实际定义主要是基于行为或不可靠的总性状，如“银色”，在过程开始后很长时间才表现出来。这些过程的分子生理学和遗传学的理解是潜在的野生和养殖的大西洋种群的管理具有重大价值。该项目将采取多管齐下的方法来解决这个问题，利用独特的专业知识和资源组合。使用在苏格兰办公室、位于阿尔蒙班克的渔业研究服务（FRS）设施和阿伯丁大学专用光周期/温度控制水族箱中在半自然条件下饲养的parr，我们将（a）评估神经内分泌系统的关键元件的表达模式，这些元件最近被证明在驱动其他脊椎动物群体生理学的季节性变化中发挥关键作用，但迄今为止尚未在鱼中探索，和（B）使用新一代超高通量测序方法来产生PST期间下丘脑/垂体和嗅上皮中基因表达的全基因组谱。这些方法将产生PST关键神经方面的上游调节因子的候选基因，并开始解决神经内分泌系统的变化在多大程度上驱动嗅觉上皮或嗅觉上皮的平行变化的问题。在进一步的实验中，这些基因的表达将被评估在PST在鱼类从高和低地流，这表明不同的PST时间。这将使我们能够定义在神经内分泌和嗅觉系统的分子事件，通过不同的时间迁移行为和生理发展。总的来说，这些研究将大大促进对PST神经生物学的理解。

In migratory Atlantic salmon, the process whereby young fish born in freshwater streams (parr) become migratory 'smolts' and go to sea represents a crucial life-history transition, involving complex behavioural and physiological changes. Most mysterious amongst these is the acquisition of an olfactory 'imprint' of the natal stream, prior to smolt migration, upon which return as adults later depends. Similarly the neural and neuroendocrine events governing the precise spring timing of the parr-smolt transition (PST) are also very poorly understood. Hence practical definition of the smolt phenotype is largely based on behaviour or unreliable gross traits such as 'silverness', manifest long after the process has been initiated. Molecular physiological and genetic understanding of these processes is potentially of major value for management of wild and farmed Atlantic populations. This project will take a multi-pronged approach to address this problem, capitalising on a unique combination of expertises and resources. Using parr reared in semi-natural conditions at the Scottish Office, Fisheries Research Services (FRS) facility at Almondbank & in dedicated photoperiod / temperature controlled aquaria at the University of Aberdeen, we will (a) assess the expression patterns of key elements of the neuroendocrine system recently shown to play a key role in driving seasonal changes in physiology in other vertebrate groups, but so far unexplored in fish and (b) use new generation ultra-high throughput sequencing methods to generate genome wide profiles of gene expression in the hypothalamus/pituitary and the olfactory epithelium during the PST. Together these approaches will yield candidate genes for upstream regulators of key neural aspects of PST, and begin to address the question of extent to which changes in the neuroendocrine system drive or parallel changes in the olfactory epithelium. In further experiments, the expression of these genes will be assessed during PST in fish from high and lowland streams, which show distinctive timing of PST. This will allow us to define the molecular events in both the neuroendocrine and olfactory systems through which differential timing of migratory behaviour and physiology develops. Collectively these studies will greatly advance understanding of the neurobiology of PST.