Molecular evolution of globin genes in Gymnotiform electric fishes: relation to hypoxia tolerance.
Molecular evolution of globin genes in Gymnotiform electric fishes: relation to hypoxia tolerance.
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DOI：
10.1186/s12862-017-0893-3
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发表时间：
2017-02-13
影响因子：
3.4
通讯作者：
Zakon H
中科院分区：
文献类型：
--
作者：
Tian R;Losilla M;Lu Y;Yang G;Zakon H
夜间活动的裸子形弱电鱼产生电信号进行通信和导航，这可能会消耗大量能量。这些鱼主要生活在亚马逊盆地，其中一些物种喜欢氧气充足的水域，而另一些则生活在缺氧、停滞的栖息地。后者表现出对缺氧耐受性的形态、生理和行为适应。然而，目前还没有在分子水平上对低氧耐受性的研究。珠蛋白是典型的呼吸蛋白。它们主要在各种组织和器官的氧结合和输送中起作用。在这里，我们研究了与其他硬骨鱼相比，12种裸子鱼的α和β血红蛋白、肌红蛋白和神经红蛋白的分子进化。本研究使用不同的最大似然（ML）方法确定了血红蛋白（Hb）和肌红蛋白（Mb）基因上的正选择位点（PSS）；一些PSS落在结构上重要的蛋白质区域。珠蛋白基因正向选择的证据表明，这些基因的适应性进化有助于增强氧的储存和运输能力。有趣的是，在专性呼吸电鳗（Electrophorus electricus）的一个关键位点上替换一个Cys，预计会增强Mb的氧储存，并有助于缺氧时NO的输送。在一种呼吸空气的非洲电鱼（Gymnarchus niloticus）中也发现了类似的Cys替代。此外，在正常缺氧条件下，两种耐缺氧物种心脏肌红蛋白和大脑神经红蛋白的高表达模式表明，选择对这些珠蛋白基因的主要影响是它们的序列，而不是它们的基础表达模式。结果表明，在大多数专性或兼性呼吸的耐缺氧裸子形鱼类中，珠蛋白基因存在明显的正选择特征。这些发现强调了珠蛋白基因在裸子鱼耐缺氧进化中的关键作用。本文的在线版本（doi:10.1186/s12862-017-0893-3）包含补充材料，可供授权用户使用。
Nocturnally active gymnotiform weakly electric fish generate electric signals for communication and navigation, which can be energetically taxing. These fish mainly inhabit the Amazon basin, where some species prefer well-oxygenated waters and others live in oxygen-poor, stagnant habitats. The latter species show morphological, physiological, and behavioral adaptations for hypoxia-tolerance. However, there have been no studies of hypoxia tolerance on the molecular level. Globins are classic respiratory proteins. They function principally in oxygen-binding and -delivery in various tissues and organs. Here, we investigate the molecular evolution of alpha and beta hemoglobins, myoglobin, and neuroglobin in 12 gymnotiforms compared with other teleost fish. The present study identified positively selected sites (PSS) on hemoglobin (Hb) and myoglobin (Mb) genes using different maximum likelihood (ML) methods; some PSS fall in structurally important protein regions. This evidence for the positive selection of globin genes suggests that the adaptive evolution of these genes has helped to enhance the capacity for oxygen storage and transport. Interestingly, a substitution of a Cys at a key site in the obligate air-breathing electric eel (Electrophorus electricus) is predicted to enhance oxygen storage of Mb and contribute to NO delivery during hypoxia. A parallel Cys substitution was also noted in an air-breathing African electric fish (Gymnarchus niloticus). Moreover, the expected pattern under normoxic conditions of high expression of myoglobin in heart and neuroglobin in the brain in two hypoxia-tolerant species suggests that the main effect of selection on these globin genes is on their sequence rather than their basal expression patterns. Results indicate a clear signature of positive selection in the globin genes of most hypoxia-tolerant gymnotiform fishes, which are obligate or facultative air breathers. These findings highlight the critical role of globin genes in hypoxia tolerance evolution of Gymnotiform electric fishes. The online version of this article (doi:10.1186/s12862-017-0893-3) contains supplementary material, which is available to authorized users.