Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, CT, USA.
Institutional Research and Planning, Fitchburg State University, Fitchburg, MA, USA.
Oecologia. 2024 Aug;205(3-4):571-586. doi: 10.1007/s00442-024-05588-x. Epub 2024 Jul 16.
Identifying how the demands of migration are met at the level of gene expression is critical for understanding migratory physiology and can potentially reveal how migratory forms evolve from nonmigratory forms and vice versa. Among fishes, migration between freshwater and seawater (diadromy) requires considerable osmoregulatory adjustments, powered by the ion pump Na, K-ATPase (NKA) in the gills. Paralogs of the catalytic α-subunit of the pump (NKA α1a and α1b) are reciprocally upregulated in fresh- and seawater, a response known as paralog-switching, in gills of some diadromous species. We tested ontogenetic changes in NKA α-subunit paralog expression patterns, comparing pre-migrant and migrant alewife (Alosa pseudoharengus) sampled in their natal freshwater environment and after 24 h in seawater. In comparison to pre-migrants, juvenile out-migrants exhibited stronger paralog switching via greater downregulation of NKA α1a in seawater. We also tested microevolutionary changes in the response, exposing juvenile diadromous and landlocked alewife to freshwater (0 ppt) and seawater (30 ppt) for 2, 5, and 15 days. Diadromous and landlocked alewife exhibited salinity-dependent paralog switching, but levels of NKA α1b transcription were higher and the decrease in NKA α1a was greater after seawater exposure in diadromous alewife. Finally, we placed alewife α-subunit NKA paralogs in a macroevolutionary context. Molecular phylogenies show alewife paralogs originated independently of paralogs in salmonids and other teleosts. This study demonstrated that NKA paralog switching is tied to halohabitat profile and that duplications of the NKA gene provided the substrate for multiple, independent molecular solutions that support a diadromous life history.
确定迁移需求在基因表达水平上是如何得到满足的，对于理解迁移生理学至关重要，并且可能揭示迁移形式如何从非迁移形式进化而来，反之亦然。在鱼类中，淡水和海水之间的洄游（洄游）需要相当大的渗透调节调整，这是由鳃中的离子泵 Na，K-ATPase（NKA）提供动力的。泵的催化α亚基的同工型（NKAα1a和α1b）在一些洄游物种的鳃中被淡水和海水相互上调，这种反应被称为同工型转换。我们测试了 NKAα亚基同工型表达模式的个体发生变化，比较了在其出生地淡水环境中采样的预洄游和洄游的鲱鱼（Alosa pseudoharengus），以及在海水中 24 小时后的情况。与预洄游者相比，幼鱼洄游者在海水中通过下调 NKAα1a 表现出更强的同工型转换。我们还测试了微进化过程中对该反应的变化，使幼鱼洄游和陆封鲱鱼暴露于淡水（0 ppt）和海水（30 ppt）中 2、5 和 15 天。洄游和陆封鲱鱼表现出依赖盐度的同工型转换，但在洄游鲱鱼中，NKAα1b 转录水平更高，在暴露于海水后 NKAα1a 的减少幅度更大。最后，我们将鲱鱼α亚基 NKA 同工型置于宏观进化背景下。分子系统发育表明，鲱鱼同工型独立于鲑鱼和其他硬骨鱼的同工型起源。这项研究表明，NKA 同工型转换与盐度生境特征有关，并且 NKA 基因的重复为支持洄游生活史的多种独立分子解决方案提供了基础。
