The origin of multicellularity in cyanobacteria.
The origin of multicellularity in cyanobacteria.
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DOI：
10.1186/1471-2148-11-45
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发表时间：
2011-02-14
影响因子：
3.4
通讯作者：
Bagheri HC
中科院分区：
文献类型：
--
作者：
Schirrmeister BE;Antonelli A;Bagheri HC
蓝藻是地球上最古老、形态最多样的原核生物门之一。大约24.5 - 22.2亿年前，含氧大气的早期发展归因于蓝藻的光合作用。此外，它们是少数进化出多细胞生物的原核生物门之一。了解多细胞生物是何时以及如何在这些古代生物中进化的，将为早期生命历史提供基本信息，并进一步加深我们对复杂生命形式的认识。我们对代表蓝藻形态和遗传多样性的大样本分类群的16S rDNA序列进行了系统发育分析并进行了比较。我们在10000棵系统发育树上重建了祖先的特征状态。结果表明，大多数现存的蓝藻起源于多细胞祖先。向单细胞细胞逆转至少发生5次。在一个单细胞分支中，至少有一次多细胞又被建立起来。与化石记录的比较支持多细胞生物的早期起源，可能早在24.5 - 22.2亿年前发生的“大氧化事件”。结果表明，多细胞形态在蓝藻谱系的早期进化，并在先前的损失后至少重新获得一次。今天蓝藻中表现出的大多数形态多样性——包括大多数单细胞物种——起源于古老的多细胞谱系。多细胞生物可能为探索新的生态位提供了相当大的优势，从而促进了新谱系的多样化。
Cyanobacteria are one of the oldest and morphologically most diverse prokaryotic phyla on our planet. The early development of an oxygen-containing atmosphere approximately 2.45 - 2.22 billion years ago is attributed to the photosynthetic activity of cyanobacteria. Furthermore, they are one of the few prokaryotic phyla where multicellularity has evolved. Understanding when and how multicellularity evolved in these ancient organisms would provide fundamental information on the early history of life and further our knowledge of complex life forms. We conducted and compared phylogenetic analyses of 16S rDNA sequences from a large sample of taxa representing the morphological and genetic diversity of cyanobacteria. We reconstructed ancestral character states on 10,000 phylogenetic trees. The results suggest that the majority of extant cyanobacteria descend from multicellular ancestors. Reversals to unicellularity occurred at least 5 times. Multicellularity was established again at least once within a single-celled clade. Comparison to the fossil record supports an early origin of multicellularity, possibly as early as the "Great Oxygenation Event" that occurred 2.45 - 2.22 billion years ago. The results indicate that a multicellular morphotype evolved early in the cyanobacterial lineage and was regained at least once after a previous loss. Most of the morphological diversity exhibited in cyanobacteria today —including the majority of single-celled species— arose from ancient multicellular lineages. Multicellularity could have conferred a considerable advantage for exploring new niches and hence facilitated the diversification of new lineages.
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DOI：
10.1098/rstb.2006.1835
发表时间：
2006-06-29
影响因子：
6.3
作者：
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