Data from: Migrate or reside: divergent energetic and immunity programs, ion pumps, and predictive markers of steelhead Oncorhynchus mykiss

Divergent life history strategies occur in steelhead or rainbow trout Oncorhynchus mykiss, and many populations produce both migrant (anadromous fish that move to the ocean after rearing) and resident (do not migrate and remain in fresh water) individuals. Mechanisms leading to each type are only partially understood; while the general tendency of a population is heritable, individual tendency may be plastic, influenced by local environment. Steelhead hatchery programmes aim to mitigate losses in wild stocks by producing trout that will migrate to the ocean and not compete with wild trout for limited freshwater resources. To increase our understanding of gill function in these migratory or resident phenotypes, here we compare gill transcriptome profiles of hatchery-released fish either at the release site (residents) or five river kilometres downstream while still in full fresh water (migrants). To test whether any of these genes can be used as predictive markers for smoltification, we compared these genes between migrant-like and undifferentiated trout while still in the hatchery in a common environment (prerelease). Results confirmed the gradual process of smoltification, and the importance of energetics, gill remodelling and ion transport capacity for migrants. Additionally, residents overexpressed transcripts involved in antiviral defences, potentially for immune surveillance via dendritic cells in the gills. The best smoltification marker candidate was protein s100a4, expression of which was highly correlated with Na(+) , K(+) ATPase (NKA) activity and smolt-like morphology in pre- and postrelease trout gills.

硬头鳟与虹鳟（Oncorhynchus mykiss）存在趋异的生活史策略，多数种群可同时产生洄游型与定居型个体：其中洄游型个体为幼体在淡水育幼后迁移至海洋的溯河鱼类，定居型个体则不进行迁徙、终生栖息于淡水。目前调控两种生活型的分子机制仅部分得到阐明；尽管种群的整体倾向具有可遗传性，但个体的发育倾向却具有表型可塑性，受当地环境因素影响。
硬头鳟孵化场繁育计划旨在通过培育可迁移至海洋的虹鳟个体，以缓解野生种群的资源损失，同时避免其与野生虹鳟争夺有限的淡水资源。为加深对洄游型与定居型表型鳃功能的理解，本研究对比了孵化场放流个体的鳃转录组谱：一类采集于放流位点（代表定居型个体），另一类采集于下游5公里河道处且仍处于纯淡水环境中的个体（代表洄游型个体）。
为验证相关基因能否作为降海变态（smoltification）的预测标记，我们在统一养殖环境的孵化场中，对放流前的类洄游型与未分化型虹鳟的相关基因表达进行了对比分析。研究结果证实，降海变态是一个渐进过程，且能量代谢、鳃组织重塑与离子转运能力对洄游型个体至关重要。此外，定居型个体的鳃组织中参与抗病毒防御的转录本表达量更高，这可能与鳃部树突状细胞介导的免疫监视功能相关。本研究筛选出的最优降海变态标记候选基因为S100A4蛋白，其表达量与放流前后虹鳟鳃组织的钠钾ATP酶（Na⁺,K⁺-ATP酶，NKA）活性及降海幼体形态特征均呈高度相关。