Flexible selection of diversified Na(+)/K(+)-ATPase α-subunit isoforms for osmoregulation in teleosts.
Flexible selection of diversified Na(+)/K(+)-ATPase α-subunit isoforms for osmoregulation in teleosts.
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DOI：
10.1186/s40851-016-0050-7
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发表时间：
2016
影响因子：
2.7
通讯作者：
Takei Y
中科院分区：
文献类型：
--
作者：
Wong MK;Pipil S;Ozaki H;Suzuki Y;Iwasaki W;Takei Y
多个Na+/K+- atp酶(NKA) α-亚基亚型在硬骨鱼中对盐度转移的响应存在差异，但我们观察到这些亚型的命名与NKA α-基因的系统发育关系不一致。我们克隆了鳗鱼和medaka的催化NKA α-亚基亚型，分析了它们从淡水（FW）转移到海水（SW）后在渗透调节组织中表达的时间过程，并进行了系统发育分析，以推断出不同复制事件如何导致硬鱼中NKA α-基因目前的基因组排列。在鳗鱼和水母中分别克隆了5个和6个α-亚基。在鳗鱼中，通常报道的α1a和α1b亚型不存在，而α1c亚型则多样化（α1c-1、α1c-2、α1c-3、α2和α3）。系统发育分析表明，大马哈鱼、罗非鱼和medaka的α1a和α1b亚型是由独立的重复事件产生的，因此它们是同源亚型。重新检查已知同种异构体在盐度胁迫后的表达变化表明，作为主要sw型的同种异构体在硬骨鱼谱系中是不同的。α1同工型的多样化发生在不同类型的基因重复，或通过串联基因之间的替代转录形成嵌合转录物，但在泛盐物种中没有更多α1拷贝的趋势。我们的数据表明，在鲑鱼中发生的FW （α1a占优势）和SW （α1b占优势）的同工型转换在硬骨鱼中并不普遍。相反，在鳗鱼中，α1c-1是SW中上调的鳃、肠和肾的主要α-亚基。NKA mRNA和蛋白的定位在西南鳗鲡的鳃和肠中一致上调，但在肾远端和集合小管中没有，在这些地方低转录表达水平伴随着高蛋白水平，这表明组织特异性的翻译调节决定和微调了NKA的表达。在medaka中，α1b在前肠SW中上调，而大多数其他α-亚基亚型对盐度变化的反应较弱。通过整合基因表达和系统发育结果，我们提出硬骨鱼对SW驯化的主要NKA α-亚基不是祖先选择的，而是以谱系特异性的方式灵活决定的。
Multiple Na+/K+-ATPase (NKA) α-subunit isoforms express differentially in response to salinity transfer in teleosts but we observed that the isoform nomenclature is inconsistent with the phylogenetic relationship of NKA α-genes. We cloned the catalytic NKA α-subunit isoforms in eels and medaka, analyzed the time course of their expressions in osmoregulatory tissues after transfer from freshwater (FW) to seawater (SW), and performed phylogenetic analyses to deduce an evolutionary scenario that illustrates how various duplication events have led to the current genomic arrangement of NKA α-genes in teleosts. Five and six α-subunits were cloned in eels and medaka respectively. In eels, the commonly-reported α1a and α1b isoforms were absent while the α1c isoform was diversified instead (α1c-1, α1c-2, α1c-3, α2, and α3 in eels). Phylogenetic estimation indicated that the α1a and α1b isoforms from salmon, tilapia, and medaka were generated by independent duplication events and thus they are paralogous isoforms. Re-examination of expression changes of known isoforms after salinity challenge revealed that the isoforms selected as predominant SW-types varied among teleost lineages. Diversification of α1 isoforms occurred by various types of gene duplication, or by alternative transcription among tandem genes to form chimeric transcripts, but there is no trend for more α1 copies in euryhaline species. Our data suggest that the isoform switching between FW (α1a predominates) and SW (α1b predominates) that occurs in salmonids is not universal in teleosts. Instead, in eels, α1c-1 was the major α-subunit upregulated gill, intestine, and kidney in SW. Localization of both NKA mRNA and protein showed consistent upregulation in gill and intestine in SW eels, but not in renal distal and collecting tubules, where low transcript expression levels were accompanied by high protein levels, suggesting a tissue-specific translational regulation that determines and fine-tunes the NKA expression. In medaka, α1b was upregulated in SW in anterior intestine while most other α-subunit isoforms were less responsive to salinity changes. By integrating gene expression and phylogenetic results, we propose that the major NKA α-subunits for SW acclimation were not ancestrally selected, but rather were flexibly determined in lineage-specific fashion in teleosts.