Capacity for freshwater acclimation and differences in the transcription of ion transporter genes underlying different migratory life histories of Takifugu fish
Capacity for freshwater acclimation and differences in the transcription of ion transporter genes underlying different migratory life histories of Takifugu fish
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东方鲀淡水适应能力及不同洄游生活史中离子转运蛋白基因转录差异
作者：
Nakamura;M.;Jiang;T.;Xu;G.;Yang;J.;Xu;P.;Watanabe;S.;Kaneko;T.;Koyama;T.;Kikuchi;K.;Tsukamoto;K.;and Otake;T.
河豚属是由大约20种河豚组成的种群，生活在东亚国家周围的各种盐度环境中。这一组呈现了广泛的进化阶段，以适应由于物种形成在很短的时间(200万-500万年)前发生在进化时间尺度上的顺序性。因此，这一群体可以被认为是研究逆行记忆进化机制的模型。我们首先对两个滨水种--五个种进行了从海水到低盐度水域的迁移实验。暗箱和T。眼镜蛇，两种常盐生游荡者海洋特产。红宝石和T。Nphobes，一种严格意义上的海洋物种。Snyderi，并证实对低渗环境的适应能力与它们的生活史策略有关。其次，利用RNA测序技术对这些物种在低渗和高渗条件下的鳃和肠的转录本进行比较，以确定在淡水适应中可能起重要作用的候选转运蛋白。由于这一分析表明，编码鳃中重要的离子转运体的cftr和编码在肠道中发挥重要渗透调节作用的转运体的ncc是重要的候选基因，它们的表达通过实时定量PCR分析得到了验证。在低渗条件下，cftr在4种真盐鱼类的鳃中表达下调，而在狭盐T的鳃中没有表达变化。Snyderi，这可能是低渗适应能力较差的原因之一。斯尼德利。在低渗条件下，Ncc在两种淡水型水生植物的肠道中表达明显上调，而在其他三种水生植物中表达不明显。不同物种间离子转运蛋白表达模式的差异表明，鳃离子转运蛋白和肠道离子转运蛋白的转录调控可能对提高竹子属植物的低渗驯化能力和顺性进化具有重要意义。
The genusTakifuguis a group of approximately 20 species of puffer fishes living in a wide range of salinity environments around East Asian countries. This group presents a broad spectrum of evolutionary stages adapted to anadromy as a result of speciation that occurred a short time (2–5 million years) ago on an evolutionary timescale. This group thus can be considered as a model for studying the evolutionary mechanisms of anadromy. We firstly conducted a transfer experiment from seawater to low-salinity waters on fiveTakifuguspecies: two anadromous speciesT. obscurusandT. ocellatus, two euryhaline wanderer marine speciesT. rubripesandT. niphobles, and a strictly marine speciesT. snyderi, and confirmed that the capacity for acclimation to hypotonic environments was associated with their life history strategies. Next, transcriptomes of the gill and intestine of these species in hypotonic condition were compared to those under hypertonic condition for each species using RNA-Sequencing so as to determine possible candidate transporters playing an important role on freshwater adaptation. As this analysis suggested thatcftr, encoding an important ion transporter for seawater acclimation in the gill, andncc, encoding a transporter that is suggested to play important osmoregulatory roles in the intestine, are important candidates, their expression was validated by quantitative real-time PCR analysis. Expression ofcftrwas downregulated in the gills of the four euryhaline species under the hypotonic condition, but no change was detected in the gill of stenohalineT. snyderi, which may be one reason for the poor hypotonic acclimation capacity ofT. snyderi. Expression ofnccwas clearly upregulated in the intestines of the two anadromous species under the hypotonic condition, but not in other three species. Different ion transporter expression patterns between the five species indicate that the transcriptional regulation ofcftrin the gill andnccin the intestine may be important for the improvement of hypotonic acclimation capacity and evolution of anadromy in theTakifuguspecies.