85
views
0
recommends
+1 Recommend
0 collections
    12
    shares
      • Record: found
      • Abstract: found
      • Article: found
      Is Open Access

      On the Archaeal Origins of Eukaryotes and the Challenges of Inferring Phenotype from Genotype

      review-article

      Read this article at

      Bookmark
          There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.

          Abstract

          If eukaryotes arose through a merger between archaea and bacteria, what did the first true eukaryotic cell look like? A major step toward an answer came with the discovery of Lokiarchaeum, an archaeon whose genome encodes small GTPases related to those used by eukaryotes to regulate membrane traffic. Although ‘Loki’ cells have yet to be seen, their existence has prompted the suggestion that the archaeal ancestor of eukaryotes engulfed the future mitochondrion by phagocytosis. We propose instead that the archaeal ancestor was a relatively simple cell, and that eukaryotic cellular organization arose as the result of a gradual transfer of bacterial genes and membranes driven by an ever-closer symbiotic partnership between a bacterium and an archaeon.

          Trends

          Eukaryotes are thought to be a product of symbiosis between archaea and bacteria. The recently discovered Lokiarchaeum (‘Loki’) encodes more Eukaryotic Signature Proteins (ESPs) than any other archaeon, making it the closest living relative to the putative ancestor of eukaryotes.

          Lokiarchaeum is the first prokaryote found to encode small GTPases, gelsolin, BAR domains, and longin domains, leading many to suggest that it might be compartmentalized and be capable of membrane trafficking.

          Many models for the evolution of eukaryotes invoke an archaeal ancestor that is capable of phagocytosis to explain the entry of the future mitochondrion into the host cell.

          Understanding the cell biology of Lokiarchaeum will be key to understanding the morphological transitions that characterized the evolution of eukaryotic cellular architecture, but Loki has not yet been cultured or seen.

          Related collections

          Most cited references65

          • Record: found
          • Abstract: found
          • Article: not found

          Horizontal gene transfer in prokaryotes: quantification and classification.

          Comparative analysis of bacterial, archaeal, and eukaryotic genomes indicates that a significant fraction of the genes in the prokaryotic genomes have been subject to horizontal transfer. In some cases, the amount and source of horizontal gene transfer can be linked to an organism's lifestyle. For example, bacterial hyperthermophiles seem to have exchanged genes with archaea to a greater extent than other bacteria, whereas transfer of certain classes of eukaryotic genes is most common in parasitic and symbiotic bacteria. Horizontal transfer events can be classified into distinct categories of acquisition of new genes, acquisition of paralogs of existing genes, and xenologous gene displacement whereby a gene is displaced by a horizontally transferred ortholog from another lineage (xenolog). Each of these types of horizontal gene transfer is common among prokaryotes, but their relative contributions differ in different lineages. The fixation and long-term persistence of horizontally transferred genes suggests that they confer a selective advantage on the recipient organism. In most cases, the nature of this advantage remains unclear, but detailed examination of several cases of acquisition of eukaryotic genes by bacteria seems to reveal the evolutionary forces involved. Examples include isoleucyl-tRNA synthetases whose acquisition from eukaryotes by several bacteria is linked to antibiotic resistance, ATP/ADP translocases acquired by intracellular parasitic bacteria, Chlamydia and Rickettsia, apparently from plants, and proteases that may be implicated in chlamydial pathogenesis.
            Bookmark
            • Record: found
            • Abstract: found
            • Article: not found

            Eukaryotic evolution, changes and challenges.

            The idea that some eukaryotes primitively lacked mitochondria and were true intermediates in the prokaryote-to-eukaryote transition was an exciting prospect. It spawned major advances in understanding anaerobic and parasitic eukaryotes and those with previously overlooked mitochondria. But the evolutionary gap between prokaryotes and eukaryotes is now deeper, and the nature of the host that acquired the mitochondrion more obscure, than ever before.
              Bookmark
              • Record: found
              • Abstract: found
              • Article: not found

              Adaptations to energy stress dictate the ecology and evolution of the Archaea.

              The three domains of life on Earth include the two prokaryotic groups, Archaea and Bacteria. The Archaea are distinguished from Bacteriabased on phylogenetic and biochemical differences, but currently there is no unifying ecological principle to differentiate these groups. The ecology of the Archaea is reviewed here in terms of cellular bioenergetics. Adaptation to chronic energy stress is hypothesized to be the crucial factor that distinguishes the Archaea from Bacteria. The biochemical mechanisms that enable archaea to cope with chronic energy stress include low-permeability membranes and specific catabolic pathways. Based on the ecological unity and biochemical adaptations among archaea, I propose the hypothesis that chronic energy stress is the primary selective pressure governing the evolution of the Archaea.
                Bookmark

                Author and article information

                Contributors
                Journal
                Trends Cell Biol
                Trends Cell Biol
                Trends in Cell Biology
                Elsevier Science Publishers
                0962-8924
                1879-3088
                1 July 2016
                July 2016
                : 26
                : 7
                : 476-485
                Affiliations
                [1 ]MRC Laboratory for Molecular Cell Biology, University College London, Gower Street, London WC1E 6BT, UK
                [2 ]National Centre for Biological Sciences, TIFR, GKVK, Bellary Road, Bengaluru 560065, India
                Author notes
                Article
                S0962-8924(16)30002-2
                10.1016/j.tcb.2016.03.009
                4917890
                27319280
                43451401-5df4-4e78-9280-2dbc854153f7
                © 2016 The Authors

                This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

                History
                Categories
                Opinion
                Special Issue: 25 Years of Trends in Cell Biology

                Cell biology
                lokiarchaeum,evolution,gtpase,eukaryogenesis
                Cell biology
                lokiarchaeum, evolution, gtpase, eukaryogenesis

                Comments

                Comment on this article