A molecular timescale of eukaryote evolution and the rise of complex multicellular life
A molecular timescale of eukaryote evolution and the rise of complex multicellular life
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DOI：
10.1186/1471-2148-4-2
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发表时间：
2004-01-28
影响因子：
3.4
通讯作者：
Shoe, JL
中科院分区：
文献类型：
--
作者：
Hedges, SB;Blair, JE;Shoe, JL
背景：地球历史上复杂多细胞生命的兴起模式和时间尚未确定。化石记录所显示的模式与分子钟所估计的模式之间存在着巨大的差异，特别是对于植物、动物、真菌和真核生物树的最深分支。在这里，我们使用了所有可用的蛋白质序列数据和分子钟方法来限制复杂性随时间的增加。我们的系统发育分析表明，（i）动物与真菌的关系比与植物的关系更密切，（ii）红藻与植物的关系比与动物或真菌的关系更密切，（iii）领鞭毛虫与动物的关系比与真菌或植物的关系更密切，（iv）藻类，裸藻动物，和泡状体都是以植物+动物+真菌为基础的，和（v）假单胞体是以其他真核生物（包括泡状体和裸藻动物）为基础的。发散时间估计从全球和本地时钟的方法，使用20 - 188蛋白质每个节点，分别处理数据（多基因）和连接（超基因）。不同的时间估计方法产生了类似的结果（5%以内）：脊椎节肢动物（9.64亿年前，Ma），刺胞纲-双脂纲（1，298 Ma），多孔菌门-真后生动物门核菌纲-厚孢菌纲（551 Ma）、酵母纲-酵母菌纲（723 Ma）、半子囊菌纲-丝状子囊菌纲（982 Ma）、担子菌纲-子囊菌纲（968 Ma）、毛霉-担子菌门（947 Ma），真菌-动物（1，513 Ma）、苔藓-维管植物（707 Ma）、绿藻-维管植物（968 Ma）、红藻-绿藻+胚藻（1，428 Ma）、植物-动物（1，609 Ma）、泡孔动物-植物+动物+真菌（1，973 Ma）、裸藻动物-植物+动物+真菌（1，961 Ma）和贾第虫-植物+动物+真菌（2，309 Ma）。通过外推，线粒体大约在2300-1800 Ma出现，质体大约在1600-1500 Ma出现。对共同祖先细胞类型的最大数量的估计，结合分歧时间，显示从2500 Ma的两种细胞类型增加到1500 Ma的10种类型和1000 Ma的50种类型。结果表明，环境中的氧气水平，以及真核生物从氧气中提取能量的能力，以及产生氧气的能力，是复杂多细胞生命兴起的关键因素。在2300 Ma氧水平初始增加后不久，线粒体和具有2-3种以上细胞类型的生物体出现。在1500 Ma时质体的加入，使真核生物能够产生氧气，在复杂性的主要上升之前。
Background: The pattern and timing of the rise in complex multicellular life during Earth's history has not been established. Great disparity persists between the pattern suggested by the fossil record and that estimated by molecular clocks, especially for plants, animals, fungi, and the deepest branches of the eukaryote tree. Here, we used all available protein sequence data and molecular clock methods to place constraints on the increase in complexity through time.Results: Our phylogenetic analyses revealed that (i) animals are more closely related to fungi than to plants, (ii) red algae are closer to plants than to animals or fungi, (iii) choanoflagellates are closer to animals than to fungi or plants, (iv) diplomonads, euglenozoans, and alveolates each are basal to plants+animals+fungi, and (v) diplomonads are basal to other eukaryotes (including alveolates and euglenozoans). Divergence times were estimated from global and local clock methods using 20 188 proteins per node, with data treated separately (multigene) and concatenated (supergene). Different time estimation methods yielded similar results (within 5%): vertebrate-arthropod (964 million years ago, Ma), Cnidaria-Bilateria (1,298 Ma), Porifera-Eumetozoa (1,351 Ma), Pyrenomycetes-Plectomycetes (551 Ma), Candida-Saccharomyces (723 Ma), Hemiascomycetes-filamentous Ascomycota (982 Ma), Basidiomycota-Ascomycota (968 Ma), Mucorales-Basidiomycota (947 Ma), Fungi-Animalia (1,513 Ma), mosses-vascular plants (707 Ma), Chlorophyta-Tracheophyta (968 Ma), Rhodophyta-Chlorophyta+Embryophyta (1,428 Ma), Plantae-Animalia (1,609 Ma), Alveolata-plants+animals+fungi (1,973 Ma), Euglenozoa-plants+animals+fungi (1,961 Ma), and Giardia-plants+animals+fungi (2,309 Ma). By extrapolation, mitochondria arose approximately 2300-1800 Ma and plastids arose 1600-1500 Ma. Estimates of the maximum number of cell types of common ancestors, combined with divergence times, showed an increase from two cell types at 2500 Ma to similar to10 types at 1500 Ma and 50 cell types at similar to1000 Ma.Conclusions: The results suggest that oxygen levels in the environment, and the ability of eukaryotes to extract energy from oxygen, as well as produce oxygen, were key factors in the rise of complex multicellular life. Mitochondria and organisms with more than 2-3 cell types appeared soon after the initial increase in oxygen levels at 2300 Ma. The addition of plastids at 1500 Ma, allowing eukaryotes to produce oxygen, preceded the major rise in complexity.