Jeffries Ken M, Connon Richard E, Verhille Christine E, Dabruzzi Theresa F, Britton Monica T, Durbin-Johnson Blythe P, Fangue Nann A
Department of Biological Sciences University of Manitoba Winnipeg Manitoba Canada.
Anatomy, Physiology & Cell Biology, School of Veterinary Medicine University of California Davis California.
Evol Appl. 2019 Apr 26;12(6):1212-1226. doi: 10.1111/eva.12799. eCollection 2019 Jun.
In estuary and coastal systems, human demand for freshwater, climate change-driven precipitation variability, and extreme weather impact salinity levels, reducing connectivity between mesohaline coastal fish populations and potentially contributing to genomic divergence. We examined gill transcriptome responses to salinity in wild-caught juveniles from two populations of Sacramento splittail (), a species of conservation concern that is endemic to the San Francisco Estuary, USA, and the lower reaches of its tributaries. Recent extreme droughts have led to salinities above the tolerance limits for this species, creating a migration barrier between these populations, which potentially contributed to population divergence. We identified transcripts involved in a conserved response to salinity; however, the more salinity-tolerant San Pablo population had greater transcriptome plasticity (3.6-fold more transcripts responded than the Central Valley population) and a response consistent with gill remodeling after 168 hr of exposure to elevated salinity. The reorganization of the gill in response to changing osmotic gradients is a process critical for acclimation and would facilitate enhanced salinity tolerance. We detected an upregulation of receptors that control the Wnt (wingless-type) cell signaling pathway that may be required for an adaptive response to increases in salinity, patterns not observed in the relatively salinity-sensitive Central Valley population. We detected 62 single nucleotide polymorphisms (SNPs) in coding regions of 26 transcripts that differed between the populations. Eight transcripts that contained SNPs were associated with immune responses, highlighting the importance of diversity in immune gene sequences as a defining characteristic of genomic divergence between these populations. Our data demonstrate that these populations have divergent transcriptomic responses to salinity, which is consistent with observed physiological differences in salinity tolerance.
在河口和沿海系统中，人类对淡水的需求、气候变化导致的降水变率以及极端天气都会影响盐度水平，减少中盐度沿海鱼类种群之间的连通性，并可能导致基因组分化。我们研究了从两个萨克拉门托裂尾鱼种群中野生捕获的幼鱼鳃转录组对盐度的反应，萨克拉门托裂尾鱼是一种受到保护关注的物种，原产于美国旧金山河口及其支流下游。最近的极端干旱导致盐度超过了该物种的耐受极限，在这些种群之间形成了迁移障碍，这可能导致了种群分化。我们鉴定出参与对盐度保守反应的转录本；然而，更耐盐的圣巴勃罗种群具有更大的转录组可塑性（响应的转录本比中央谷地种群多3.6倍），并且在暴露于高盐度168小时后，其反应与鳃重塑一致。鳃因渗透压梯度变化而进行的重组是适应过程中的关键步骤，有助于提高耐盐性。我们检测到控制Wnt（无翅型）细胞信号通路的受体上调，这可能是对盐度增加的适应性反应所必需的，而在相对盐敏感的中央谷地种群中未观察到这种模式。我们在26个转录本的编码区域检测到62个单核苷酸多态性（SNP），这些转录本在种群之间存在差异。八个含有SNP的转录本与免疫反应相关，突出了免疫基因序列多样性作为这些种群之间基因组分化的一个决定性特征的重要性。我们的数据表明，这些种群对盐度具有不同的转录组反应，这与观察到的耐盐生理差异一致。
