PDF(Pubmed)
Abstract：
Extreme weather poses huge challenges for animals that must adapt to wide variations in environmental temperature and, in many cases, it can lead to the local extirpation of populations or even the extinction of an entire species. Previous studies have found that one element of amphibian adaptation to environmental stress involves changes in mitochondrial gene expression at low temperatures. However, to date, comparative studies of gene expression in organisms living at extreme temperatures have focused mainly on nuclear genes. This study sequenced the complete mitochondrial genomes of five Asian hylid frog species: Dryophytes japonicus, D. immaculata, Hyla annectans, H. chinensis and H. zhaopingensis. It compared the phylogenetic relationships within the Hylidae family and explored the association between mitochondrial gene expression and evolutionary adaptations to cold stress. The present results showed that in D. immaculata, transcript levels of 12 out of 13 mitochondria genes were significantly reduced under cold exposure (p < 0.05); hence, we put forward the conjecture that D. immaculata adapts by entering a hibernation state at low temperature. In H. annectans, the transcripts of 10 genes (ND1, ND2, ND3, ND4, ND4L, ND5, ND6, COX1, COX2 and ATP8) were significantly reduced in response to cold exposure, and five mitochondrial genes in H. chinensis (ND1, ND2, ND3, ND4L and ATP6) also showed significantly reduced expression and transcript levels under cold conditions. By contrast, transcript levels of ND2 and ATP6 in H. zhaopingensis were significantly increased at low temperatures, possibly related to the narrow distribution of this species primarily at low latitudes. Indeed, H. zhaopingensis has little ability to adapt to low temperature (4 °C), or maybe to enter into hibernation, and it shows metabolic disorder in the cold. The present study demonstrates that the regulatory trend of mitochondrial gene expression in amphibians is correlated with their ability to adapt to variable climates in extreme environments. These results can predict which species are more likely to undergo extirpation or extinction with climate change and, thereby, provide new ideas for the study of species extinction in highly variable winter climates.
摘要：
极端天气对必须适应环境温度变化的动物提出了巨大挑战，在许多情况下,它可能导致种群的局部灭绝，甚至整个物种的灭绝。先前的研究发现，两栖动物适应环境胁迫的一个因素涉及低温下线粒体基因表达的变化。然而,到目前为止,在极端温度下生活的生物体中基因表达的比较研究主要集中在核基因上。这项研究对五种亚洲长尾蛙的完整线粒体基因组进行了测序：日本龙叶树，D.immaculata,HylaAnnectans,中国和昭平。它比较了Hylidae家族中的系统发育关系，并探索了线粒体基因表达与对冷胁迫的进化适应之间的关联。目前的结果表明，在D.immaculata中，13种线粒体基因中的12种转录水平在冷暴露下显著降低(p<0.05);因此,我们提出了D.immaculata通过在低温下进入休眠状态来适应的猜想。在H.Annectans中，10个基因的转录本(ND1，ND2，ND3，ND4，ND4L，ND5，ND6，COX1，COX2和ATP8）响应于冷暴露而显着降低，在寒冷条件下，中国的五个线粒体基因（ND1，ND2，ND3，ND4L和ATP6）也显示出显着降低的表达和转录水平。相比之下,Zhaopingensis的ND2和ATP6转录水平在低温下显著增加，可能与该物种主要在低纬度的狭窄分布有关。的确,H.zhaopingensis对低温（4°C）的适应能力很小，或者进入冬眠，它在寒冷中表现出代谢紊乱。本研究表明，两栖动物线粒体基因表达的调控趋势与其在极端环境中适应可变气候的能力有关。这些结果可以预测哪些物种更有可能随着气候变化而灭绝或灭绝，因此，为研究冬季气候高度变化的物种灭绝提供新思路。
