基于转录组分析红耳龟盐度适应的离子调节

Salinity Adaptation in Ions Adjustments of the Red-eared Slider Turtle Using Liver Transcriptomic Data

外来有害入侵物种红耳龟（Trachemys scripta elegans）,原属于淡水龟类,但目前研究发现其可存活于半咸水环境中,这使得未来红耳龟可入侵的潜在范围及危害将增大。为了探究红耳龟对盐度适应的分子机制,本研究应用高通量转录组测序技术,分析其在不同盐度环境中参与离子调节的主要基因及通路。我们设计了三个处理组：对照组（自来水）、低盐度组（0.5%,即盐度5组）和高盐度组（1.5%,即盐度15组）,慢性胁迫8周后,分析血液中无机离子、葡萄糖及皮质醇含量,并对其肝脏转录组数据进行分析。结果表明,与对照组相比,盐度5组血液渗透压、[Na＋]和血糖差异不显著（p〉0.05）,而盐度15组显著升高;血液[Cl-]三组间差异均显著;两个盐度处理组血液[K＋]显著低于对照组（p〈0.05）;但血液皮质醇含量在三组之间差异均不显著。GO （Gene ontology）富集分析发现,参与离子调节的基因主要有电压门控钾通道亚家族5 （KCNH5）、电压门控钠通道I （SCN1B）、利尿肽前体A （NPPA）、ATP酶（ATPeFOA, MTATP6, ATP6）、葡萄糖激酶（GCK）、盐诱导激酶（SIK）、脂联素（ACDC）和类固醇17α-单氧酶（CYP17A）等。所筛选出的基因大多被富集到与能量代谢、脂肪代谢、碳水化合物代谢以及内分泌系统等KEGG通路类别中。综上所述,红耳龟在盐度适应过程中参与离子调节的大部分KEGG通路以及相关的生理指标均未发生显著变化,说明它能较好地适应慢性低盐度胁迫（盐度0.5%左右）。

Red-eared Slider （Trachemys scripta elegans）, as freshwater turtles, could survive in brackish water, which maybe augment the potential scope and endangerment of invasion in the future. To investigate the molecular mechanism of salinity adaptation in T. s. elegans, the high-throughput RNA-Seq was used to discover the gene expression profiles and pathways in the study. T. s. elegans were divided into different salinities groups of 0.5% （salinity 5 group）, 1.5% （salinity 15 group） and control group （isopyknic tap-water） to conduct chronic salinity stress for eight weeks. The results showed that： Blood osmotic pressure, plasma glucose and [Na＋] in the group of salinity 15 is significantly higher than those in the control, while no difference between salinity 5 and the control. Plasma [K＋] in salinity 5 and 15 were significantly higher than the control, and plasma [CI] was significantly diffeentbetween these three groups （p〈0.05）. There was no significant difference in plasma cortisol between the three groups. Through the analysis of GO （Gene ontology）, the genes involving in ions adjustment mainly include potassium voltage-gated channel Eag-related subfamily H member 5 （KCNH5）, voltage-gated sodium channel type I beta （SCN1B）, natriuretic peptide precursor A （NPPA）, ATPase （ATPeFOA, MTATP6, ATP6）, glucokinase （GCK）, salt inducible kinase （SIK）, adiponectin （ACDC） and steroid 17alpha-monooxygenase/17alpha-hydroxyprogesterone deacetylase （CYP17A）, etc. All of the screening genes were mainly enriched in the KEGG pathways of energy metabolism, lipid metabolism, carbonhydrate metabolism and endocrine system. In conclusion, T. s. elegam can acclimatize itself to chronic salinity stress （about salinity 0.5%）.