Unique Genomic and Phenotypic Responses to Extreme and Variable pH Conditions in Purple Urchin Larvae
Unique Genomic and Phenotypic Responses to Extreme and Variable pH Conditions in Purple Urchin Larvae
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紫海胆幼虫对极端和可变 pH 条件的独特基因组和表型反应
DOI：
10.1093/icb/icaa072
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发表时间：
2020
影响因子：
2.6
通讯作者：
Pespeni, Melissa H
中科院分区：
文献类型：
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作者：
Garrett, April D;Brennan, Reid S;Steinhart, Anya L;Pelletier, Aubrey M;Pespeni, Melissa H
物种所经历的跨时空环境变化可以促进遗传多样性的维持，从而适应未来的全球变化条件。选择实验表明，紫海胆（Strongylocentrotus purpuratus）种群具有适应性遗传变异，能够在自然条件的“边缘”（pH 7.5）条件下生存。然而，对于种群是否存在遗传变异以适应目前在自然界中经历的低pH事件，或者pH条件的变化如何影响生物体和遗传反应，人们知之甚少。在这里，我们量化了实验选择的紫色海胆幼虫在静态和可变条件下的存活、生长和等位基因频率变化，这些条件分别是pH 8.1（对照）、pH 7.5（范围边缘）和pH 7.0（极端）。相对于静态处理，可变处理恢复了体型，但导致更高的死亡率，这表明在pH胁迫下生存和生长之间存在潜在的权衡。然而，在每个pH值水平内，等位基因频率的变化在静态和可变条件之间重叠，这表明无论变化如何，平均pH值的生存都具有共同的遗传基础。相比之下，对pH 7.5（边缘）和pH 7.0（极端）条件的遗传反应是不同的，表明生存的独特遗传基础。此外，选择下的位点更有可能位于外显子区，而不是调控区，这表明选择针对的是蛋白质编码变异。在更类似于自然界周期性经历的可变pH 7.5条件下选择的基因座执行与脂质生物合成和代谢相关的功能，而在静态pH 7.0条件下选择的基因座执行与跨膜和线粒体过程相关的功能。虽然这些结果很有希望，因为紫色海胆种群具有遗传变异，可以在自然界中目前没有经历过的极端pH条件下生存，但他们警告说，酸化的增加不会导致线性反应，而是会引起独特的生理压力和生存机制。
Environmental variation experienced by a species across space and time can promote the maintenance of genetic diversity that may be adaptive in future global change conditions. Selection experiments have shown that purple sea urchin,Strongylocentrotus purpuratus, populations have adaptive genetic variation for surviving pH conditions at the “edge” (pH 7.5) of conditions experienced in nature. However, little is known about whether populations have genetic variation for surviving low-pH events beyond those currently experienced in nature or how variation in pH conditions affects organismal and genetic responses. Here, we quantified survival, growth, and allele frequency shifts in experimentally selected developing purple sea urchin larvae in static and variable conditions at three pH levels: pH 8.1 (control), pH 7.5 (edge-of-range), and pH 7.0 (extreme). Variable treatments recovered body size relative to static treatments, but resulted in higher mortality, suggesting a potential tradeoff between survival and growth under pH stress. However, within each pH level, allele frequency changes were overlapping between static and variable conditions, suggesting a shared genetic basis underlying survival to mean pH regardless of variability. In contrast, genetic responses to pH 7.5 (edge) versus pH 7.0 (extreme) conditions were distinct, indicating a unique genetic basis of survival. In addition, loci under selection were more likely to be in exonic regions than regulatory, indicating that selection targeted protein-coding variation. Loci under selection in variable pH 7.5 conditions, more similar to conditions periodically experienced in nature, performed functions related to lipid biosynthesis and metabolism, while loci under selection in static pH 7.0 conditions performed functions related to transmembrane and mitochondrial processes. While these results are promising in that purple sea urchin populations possess genetic variation for surviving extreme pH conditions not currently experienced in nature, they caution that increased acidification does not result in a linear response but elicits unique physiological stresses and survival mechanisms.