The Great Oxidation Event expanded the genetic repertoire of arsenic metabolism and cycling
The Great Oxidation Event expanded the genetic repertoire of arsenic metabolism and cycling
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DOI：
10.1073/pnas.2001063117
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发表时间：
2020-05-12
影响因子：
11.1
通讯作者：
Zhu, Yong-Guan
中科院分区：
文献类型：
--
作者：
Chen, Song-Can;Sun, Guo-Xin;Zhu, Yong-Guan
大约24亿年前，早期地球上氧气的增加重组了有害金属（loids）的氧化还原循环，包括砷的氧化还原循环，这无疑对生命的生理和多样化构成了实质性的障碍。由于缺乏化石记录，评估适应性生物对这些环境挑战的反应本质上是困难的。在这里，我们应用分子钟分析参与砷抗性和循环的主要途径的13个基因家族，探索早期砷代谢循环的性质，并破译与行星氧化相关的反馈。我们的研究结果揭示了新生抗砷系统的出现在缺氧环境下早于大氧化事件（GOE），主要功能是解毒还原砷化合物，丰富的太古代环境。为了科普随着地球大气中氧气的积累而发生的氧化砷物种的毒性增加，我们发现部分预先存在的三价砷解毒系统与新出现的起源于趋同进化的途径合并。通过将氧依赖性酶途径纳入解毒网络，进一步扩大抗砷系统是可行的。这些遗传创新，再加上对其他氧化还原敏感金属的适应性反应，为生物体提供了新的机制，以适应GOE导致的全球生物周期的变化。
The rise of oxygen on the early Earth about 2.4 billion years ago reorganized the redox cycle of harmful metal(loids), including that of arsenic, which doubtlessly imposed substantial barriers to the physiology and diversification of life. Evaluating the adaptive biological responses to these environmental challenges is inherently difficult because of the paucity of fossil records. Here we applied molecular clock analyses to 13 gene families participating in principal pathways of arsenic resistance and cycling, to explore the nature of early arsenic biogeocycles and decipher feedbacks associated with planetary oxygenation. Our results reveal the advent of nascent arsenic resistance systems under the anoxic environment predating the Great Oxidation Event (GOE), with the primary function of detoxifying reduced arsenic compounds that were abundant in Archean environments. To cope with the increased toxicity of oxidized arsenic species that occurred as oxygen built up in Earth's atmosphere, we found that parts of preexisting detoxification systems for trivalent arsenicals were merged with newly emerged pathways that originated via convergent evolution. Further expansion of arsenic resistance systems was made feasible by incorporation of oxygen-dependent enzymatic pathways into the detoxification network. These genetic innovations, together with adaptive responses to other redoxsensitive metals, provided organisms with novel mechanisms for adaption to changes in global biogeocycles that emerged as a consequence of the GOE.