Hofstatter Paulo G, Tice Alexander K, Kang Seungho, Brown Matthew W, Lahr Daniel J G
Department of Zoology, Universidade de São Paulo/USP, Cidade Universitária, São Paulo, Brazil.
Department of Biological Sciences, Mississippi State University, Mississippi State, MS 39762, USA Institute for Genomics, Biocomputing and Biotechnology, Mississippi State University, Mississippi State, MS 39762, USA.
Proc Biol Sci. 2016 Oct 12;283(1840). doi: 10.1098/rspb.2016.1453.
Recombinase enzymes promote DNA repair by homologous recombination. The genes that encode them are ancestral to life, occurring in all known dominions: viruses, Eubacteria, Archaea and Eukaryota. Bacterial recombinases are also present in viruses and eukaryotic groups (supergroups), presumably via ancestral events of lateral gene transfer. The eukaryotic recA genes have two distinct origins (mitochondrial and plastidial), whose acquisition by eukaryotes was possible via primary (bacteria-eukaryote) and/or secondary (eukaryote-eukaryote) endosymbiotic gene transfers (EGTs). Here we present a comprehensive phylogenetic analysis of the recA genealogy, with substantially increased taxonomic sampling in the bacteria, viruses, eukaryotes and a special focus on the key eukaryotic supergroup Amoebozoa, earlier represented only by Dictyostelium We demonstrate that several major eukaryotic lineages have lost the bacterial recombinases (including Opisthokonta and Excavata), whereas others have retained them (Amoebozoa, Archaeplastida and the SAR-supergroups). When absent, the bacterial recA homologues may have been lost entirely (secondary loss of canonical mitochondria) or replaced by other eukaryotic recombinases. RecA proteins have a transit peptide for organellar import, where they act. The reconstruction of the RecA phylogeny with its EGT events presented here retells the intertwined evolutionary history of eukaryotes and bacteria, while further illuminating the events of endosymbiosis in eukaryotes by expanding the collection of widespread genes that provide insight to this deep history.
重组酶通过同源重组促进DNA修复。编码这些酶的基因是生命起源时就存在的，存在于所有已知的生物领域：病毒、真细菌、古细菌和真核生物。细菌重组酶也存在于病毒和真核生物类群（超群）中，大概是通过横向基因转移的祖先事件。真核生物的recA基因有两个不同的起源（线粒体和质体），真核生物通过初级（细菌-真核生物）和/或次级（真核生物-真核生物）内共生基因转移（EGT）获得了这些基因。在这里，我们对recA谱系进行了全面的系统发育分析，大大增加了细菌、病毒、真核生物的分类取样，并特别关注关键的真核生物超群变形虫门，该门此前仅由盘基网柄菌代表。我们证明，几个主要的真核生物谱系已经失去了细菌重组酶（包括后鞭毛生物和挖掘类生物），而其他谱系则保留了它们（变形虫门、原始色素体生物和SAR超群）。当不存在时，细菌recA同源物可能已经完全丢失（典型线粒体的二次丢失）或被其他真核生物重组酶取代。RecA蛋白有一个用于细胞器导入的转运肽，并在细胞器中发挥作用。这里展示的RecA系统发育及其EGT事件的重建，重新讲述了真核生物和细菌相互交织的进化历史，同时通过扩大广泛存在的基因集合，进一步阐明了真核生物内共生事件，这些基因有助于深入了解这段悠久的历史。
