1
|
Gondhalekar R, Kempes CP, McGlynn SE. Scaling of Protein Function across the Tree of Life. Genome Biol Evol 2023; 15:evad214. [PMID: 38007693 PMCID: PMC10715193 DOI: 10.1093/gbe/evad214] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2023] [Revised: 11/07/2023] [Accepted: 11/12/2023] [Indexed: 11/28/2023] Open
Abstract
Scaling laws are a powerful way to compare genomes because they put all organisms onto a single curve and reveal nontrivial generalities as genomes change in size. The abundance of functional categories across genomes has previously been found to show power law scaling with respect to the total number of functional categories, suggesting that universal constraints shape genomic category abundance. Here, we look across the tree of life to understand how genome evolution may be related to functional scaling. We revisit previous observations of functional genome scaling with an expanded taxonomy by analyzing 3,726 bacterial, 220 archaeal, and 79 unicellular eukaryotic genomes. We find that for some functional classes, scaling is best described by multiple exponents, revealing previously unobserved shifts in scaling as genome-encoded protein annotations increase or decrease. Furthermore, we find that scaling varies between phyletic groups at both the domain and phyla levels and is less universal than previously thought. This variability in functional scaling is not related to taxonomic phylogeny resolved at the phyla level, suggesting that differences in cell plan or physiology outweigh broad patterns of taxonomic evolution. Since genomes are maintained and replicated by the functional proteins encoded by them, these results point to functional degeneracy between taxonomic groups and unique evolutionary trajectories toward these. We also find that individual phyla frequently span scaling exponents of functional classes, revealing that individual clades can move across scaling exponents. Together, our results reveal unique shifts in functions across the tree of life and highlight that as genomes grow or shrink, proteins of various functions may be added or lost.
Collapse
Affiliation(s)
- Riddhi Gondhalekar
- Earth-Life Science Institute, Tokyo Institute of Technology, Tokyo, Japan
- School of Life Sciences and Technology, Tokyo Institute of Technology, Tokyo, Japan
| | | | - Shawn Erin McGlynn
- Earth-Life Science Institute, Tokyo Institute of Technology, Tokyo, Japan
- School of Life Sciences and Technology, Tokyo Institute of Technology, Tokyo, Japan
- Blue Marble Space Institute of Science, Seattle, Washington, USA
- Center for Sustainable Resource Science, RIKEN, Saitama, Japan
| |
Collapse
|
2
|
Sidorova A, Tverdislov V, Levashova N, Garaeva A. A model of autowave self-organization as a hierarchy of active media in the biological evolution. Biosystems 2020; 198:104234. [PMID: 32889101 DOI: 10.1016/j.biosystems.2020.104234] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Revised: 08/23/2020] [Accepted: 08/24/2020] [Indexed: 11/28/2022]
Abstract
Within the framework of the active media concept, we develop a biophysical model of autowave self-organization which is treated as a hierarchy of active media in the evolution of the biosphere. We also propose a mathematical model of the autowave process of speciation in a flow of mutations for the three main taxonometric groups (prokaryotes, unicellular and multicellular eukaryotes) with a naturally determined lower boundary of living matter (the appearance of prokaryotes) and an open upper boundary for the formation of new species. It is shown that the fluctuation-bifurcation description of the evolution for the formation of new taxonometric groups as a trajectory of transformation of small fluctuations into giant ones adequately reflects the process of self-organization during the formation of taxa. The major concepts of biological evolution, conditions of hierarchy formation as a fundamental manifestation of self-organization and complexity in the evolution of biological systems are considered.
Collapse
Affiliation(s)
- Alla Sidorova
- Department of Biophysics, Faculty of Physics, Lomonosov Moscow State University, Moscow, 119991, Russia.
| | - Vsevolod Tverdislov
- Head of the Department of Biophysics, Faculty of Physics, Lomonosov Moscow State University, Moscow, 119991, Russia.
| | - Natalia Levashova
- Department of Mathematics, Faculty of Physics, Lomonosov Moscow State University, Moscow, 119991, Russia.
| | - Anastasia Garaeva
- Postgraduate Student of the Department of Biophysics, Faculty of Physics, Lomonosov Moscow State University, Moscow, 119991, Russia.
| |
Collapse
|
3
|
Furubayashi T, Ueda K, Bansho Y, Motooka D, Nakamura S, Mizuuchi R, Ichihashi N. Emergence and diversification of a host-parasite RNA ecosystem through Darwinian evolution. eLife 2020; 9:e56038. [PMID: 32690137 PMCID: PMC7378860 DOI: 10.7554/elife.56038] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Accepted: 07/01/2020] [Indexed: 12/11/2022] Open
Abstract
In prebiotic evolution, molecular self-replicators are considered to develop into diverse, complex living organisms. The appearance of parasitic replicators is believed inevitable in this process. However, the role of parasitic replicators in prebiotic evolution remains elusive. Here, we demonstrated experimental coevolution of RNA self-replicators (host RNAs) and emerging parasitic replicators (parasitic RNAs) using an RNA-protein replication system we developed. During a long-term replication experiment, a clonal population of the host RNA turned into an evolving host-parasite ecosystem through the continuous emergence of new types of host and parasitic RNAs produced by replication errors. The host and parasitic RNAs diversified into at least two and three different lineages, respectively, and they exhibited evolutionary arms-race dynamics. The parasitic RNA accumulated unique mutations, thus adding a new genetic variation to the whole replicator ensemble. These results provide the first experimental evidence that the coevolutionary interplay between host-parasite molecules plays a key role in generating diversity and complexity in prebiotic molecular evolution.
Collapse
Affiliation(s)
- Taro Furubayashi
- Laboratoire Gulliver, CNRS, ESPCI Paris,
PSL Research UniversityParisFrance
| | - Kensuke Ueda
- Department of Life Science, Graduate
School of Arts and Science, The University of
TokyoTokyoJapan
| | - Yohsuke Bansho
- Graduate School of Frontier Biosciences,
Osaka UniversityOsakaJapan
| | - Daisuke Motooka
- Research Institute for Microbial
Diseases, Osaka UniversityOsakaJapan
| | - Shota Nakamura
- Research Institute for Microbial
Diseases, Osaka UniversityOsakaJapan
| | - Ryo Mizuuchi
- Komaba Institute for Science, The
University of TokyoTokyoJapan
- JST,
PRESTOKawaguchiJapan
| | - Norikazu Ichihashi
- Department of Life Science, Graduate
School of Arts and Science, The University of
TokyoTokyoJapan
- Graduate School of Frontier Biosciences,
Osaka UniversityOsakaJapan
- Komaba Institute for Science, The
University of TokyoTokyoJapan
- Universal Biology Institute, The
University of TokyoTokyoJapan
| |
Collapse
|
4
|
Shuffling type of biological evolution based on horizontal gene transfer and the biosphere gene pool hypothesis. Biosystems 2020; 193-194:104131. [DOI: 10.1016/j.biosystems.2020.104131] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2019] [Revised: 03/12/2020] [Accepted: 03/12/2020] [Indexed: 02/08/2023]
|
5
|
Abstract
The molecular clock is a valuable and widely used tool for estimating evolutionary rates and timescales in biological research. There has been considerable progress in the theory and practice of molecular clocks over the past five decades. Although the idea of a molecular clock was originally put forward in the context of protein evolution and advanced using various biochemical techniques, it is now primarily applied to analyses of DNA sequences. An interesting but very underappreciated aspect of molecular clocks is that they can be based on genetic data other than DNA or protein sequences. For example, evolutionary timescales can be estimated using microsatellites, protein folds, and even the extent of recombination. These genome features hold great potential for molecular dating, particularly in cases where nucleotide sequences might be uninformative or unreliable. Here we present an outline of the different genetic data types that have been used for molecular dating, and we describe the features that good molecular clocks should possess. We hope that our article inspires further work on the genome as an evolutionary timepiece.
Collapse
Affiliation(s)
- Simon Y W Ho
- School of Life and Environmental Sciences, University of Sydney, Sydney, NSW, Australia
| | - Amanda X Y Chen
- School of Life and Environmental Sciences, University of Sydney, Sydney, NSW, Australia
| | - Luana S F Lins
- School of Life and Environmental Sciences, University of Sydney, Sydney, NSW, Australia
| | - David A Duchêne
- School of Life and Environmental Sciences, University of Sydney, Sydney, NSW, Australia
| | - Nathan Lo
- School of Life and Environmental Sciences, University of Sydney, Sydney, NSW, Australia
| |
Collapse
|
6
|
Davies PCW, Walker SI. The hidden simplicity of biology. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2016; 79:102601. [PMID: 27608530 DOI: 10.1088/0034-4885/79/10/102601] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Life is so remarkable, and so unlike any other physical system, that it is tempting to attribute special factors to it. Physics is founded on the assumption that universal laws and principles underlie all natural phenomena, but is it far from clear that there are 'laws of life' with serious descriptive or predictive power analogous to the laws of physics. Nor is there (yet) a 'theoretical biology' in the same sense as theoretical physics. Part of the obstacle in developing a universal theory of biological organization concerns the daunting complexity of living organisms. However, many attempts have been made to glimpse simplicity lurking within this complexity, and to capture this simplicity mathematically. In this paper we review a promising new line of inquiry to bring coherence and order to the realm of biology by focusing on 'information' as a unifying concept.
Collapse
Affiliation(s)
- Paul C W Davies
- Beyond Center for Fundamental Concepts in Science, Arizona State University, Tempe, AZ, USA
| | | |
Collapse
|
7
|
Sharov AA. Coenzyme world model of the origin of life. Biosystems 2016; 144:8-17. [PMID: 26968100 PMCID: PMC4875852 DOI: 10.1016/j.biosystems.2016.03.003] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2016] [Revised: 03/03/2016] [Accepted: 03/04/2016] [Indexed: 12/23/2022]
Abstract
The origin of life means the emergence of heritable and evolvable self-reproduction. However the mechanisms of primordial heredity were different from those in contemporary cells. Here I argue that primordial life had no nucleic acids; instead heritable signs were represented by isolated catalytically active self-reproducing molecules, similar to extant coenzymes, which presumably colonized surfaces of oil droplets in water. The model further assumes that coenzyme-like molecules (CLMs) changed surface properties of oil droplets (e.g., by oxidizing terminal carbons), and in this way created and sustained favorable conditions for their own self-reproduction. Such niche-dependent self-reproduction is a necessary condition for cooperation between different kinds of CLMs because they have to coexist in the same oil droplets and either succeed or perish together. Additional kinds of hereditary molecules were acquired via coalescence of oil droplets carrying different kinds of CLMs or via modification of already existing CLMs. Eventually, polymerization of CLMs became controlled by other polymers used as templates; and this kind of template-based synthesis eventually resulted in the emergence of RNA-like replicons. Apparently, oil droplets transformed into the outer membrane of cells via engulfing water, stabilization of the surface, and osmoregulation. In result, the metabolism was internalized allowing cells to accumulate free-floating resources (e.g., animoacids, ATP), which was a necessary condition for the development of protein synthesis. Thus, life originated from simple but already functional molecules, and its gradual evolution towards higher complexity was driven by cooperation and natural selection.
Collapse
Affiliation(s)
- Alexei A Sharov
- National Institute on Aging, Genetics Laboratory, 251 Bayview Blvd., Baltimore, MD 21224, USA.
| |
Collapse
|
8
|
Sharov AA. Evolutionary constraints or opportunities? Biosystems 2014; 123:9-18. [PMID: 25047708 DOI: 10.1016/j.biosystems.2014.06.004] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2014] [Revised: 04/14/2014] [Accepted: 04/14/2014] [Indexed: 12/24/2022]
Abstract
Natural selection is traditionally viewed as a leading factor of evolution, whereas variation is assumed to be random and non-directional. Any order in variation is attributed to epigenetic or developmental constraints that can hinder the action of natural selection. In contrast I consider the positive role of epigenetic mechanisms in evolution because they provide organisms with opportunities for rapid adaptive change. Because the term "constraint" has negative connotations, I use the term "regulated variation" to emphasize the adaptive nature of phenotypic variation, which helps populations and species to survive and evolve in changing environments. The capacity to produce regulated variation is a phenotypic property, which is not described in the genome. Instead, the genome acts as a switchboard, where mostly random mutations switch "on" or "off" preexisting functional capacities of organism components. Thus, there are two channels of heredity: informational (genomic) and structure-functional (phenotypic). Functional capacities of organisms most likely emerged in a chain of modifications and combinations of more simple ancestral functions. The role of DNA has been to keep records of these changes (without describing the result) so that they can be reproduced in the following generations. Evolutionary opportunities include adjustments of individual functions, multitasking, connection between various components of an organism, and interaction between organisms. The adaptive nature of regulated variation can be explained by the differential success of lineages in macro-evolution. Lineages with more advantageous patterns of regulated variation are likely to produce more species and secure more resources (i.e., long-term lineage selection).
Collapse
Affiliation(s)
- Alexei A Sharov
- National Institute on Aging, Genetics Laboratory, 251 Bayview Blvd., Baltimore, MD 21224, USA.
| |
Collapse
|
9
|
Sharov AA. WITHDRAWN: Evolutionary constraints or opportunities? Biosystems 2014. [DOI: 10.1016/j.biosystems.2014.05.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
10
|
Sharov AA. Evolutionary constraints or opportunities? Biosystems 2014; 120C:21-30. [PMID: 24769155 PMCID: PMC4206685 DOI: 10.1016/j.biosystems.2014.04.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2014] [Revised: 04/14/2014] [Accepted: 04/14/2014] [Indexed: 01/05/2023]
Abstract
Natural selection is traditionally viewed as a leading factor of evolution, whereas variation is assumed to be random and non-directional. Any order in variation is attributed to epigenetic or developmental constraints that can hinder the action of natural selection. In contrast I consider the positive role of epigenetic mechanisms in evolution because they provide organisms with opportunities for rapid adaptive change. Because the term "constraint" has negative connotations, I use the term "regulated variation" to emphasize the adaptive nature of phenotypic variation, which helps populations and species to survive and evolve in changing environments. The capacity to produce regulated variation is a phenotypic property, which is not described in the genome. Instead, the genome acts as a switchboard, where mostly random mutations switch "on" or "off" preexisting functional capacities of organism components. Thus, there are two channels of heredity: informational (genomic) and structure-functional (phenotypic). Functional capacities of organisms most likely emerged in a chain of modifications and combinations of more simple ancestral functions. The role of DNA has been to keep records of these changes (without describing the result) so that they can be reproduced in the following generations. Evolutionary opportunities include adjustments of individual functions, multitasking, connection between various components of an organism, and interaction between organisms. The adaptive nature of regulated variation can be explained by the differential success of lineages in macro-evolution. Lineages with more advantageous patterns of regulated variation are likely to produce more species and secure more resources (i.e., long-term lineage selection).
Collapse
Affiliation(s)
- Alexei A Sharov
- National Institute on Aging, Genetics Laboratory, 251 Bayview Blvd., Baltimore, MD 21224, USA.
| |
Collapse
|
11
|
Marzban C, Viswanathan R, Yurtsever U. Earth before life. Biol Direct 2014; 9:1. [PMID: 24405803 PMCID: PMC3892030 DOI: 10.1186/1745-6150-9-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2013] [Accepted: 12/23/2013] [Indexed: 12/02/2022] Open
Abstract
Background A recent study argued, based on data on functional genome size of major phyla, that there is evidence life may have originated significantly prior to the formation of the Earth. Results Here a more refined regression analysis is performed in which 1) measurement error is systematically taken into account, and 2) interval estimates (e.g., confidence or prediction intervals) are produced. It is shown that such models for which the interval estimate for the time origin of the genome includes the age of the Earth are consistent with observed data. Conclusions The appearance of life after the formation of the Earth is consistent with the data set under examination. Reviewers This article was reviewed by Yuri Wolf, Peter Gogarten, and Christoph Adami.
Collapse
Affiliation(s)
- Caren Marzban
- Applied Physics Laboratory, Univ, of Washington, Seattle, WA, 98105-6698, USA.
| | | | | |
Collapse
|
12
|
Redi CA, Capanna E. Genome size evolution: sizing mammalian genomes. Cytogenet Genome Res 2012; 137:97-112. [PMID: 22627028 DOI: 10.1159/000338820] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
The study of genome size (GS) and its variation is so fascinating to the scientific community because it constitutes the link between the present-day analytical and molecular studies of the genome and the old trunk of the holistic and synthetic view of the genome. The GS of several taxa vary over a broad range and do not correlate with the complexity of the organisms (the C-value paradox). However, the biology of transposable elements has let us reach a satisfactory view of the molecular mechanisms that give rise to GS variation and novelties, providing a less perplexing view of the significance of the GS (C-enigma). The knowledge of the composition and structure of a genome is a pre-requisite for trying to understand the evolution of the main genome signature: its size. The radiation of mammals provides an approximately 180-million-year test case for theories of how GS evolves. It has been found from data-mining GS databases that GS is a useful cyto-taxonomical instrument at the level of orders/superorders, providing genomic signatures characterizing Monotremata, Marsupialia, Afrotheria, Xenarthra, Laurasiatheria, and Euarchontoglires. A hypothetical ancestral mammalian-like GS of 2.9-3.7 pg has been suggested. This value appears compatible with the average values calculated for the high systematic levels of the extant Monotremata (∼2.97 pg) and Marsupialia (∼4.07 pg), suggesting invasion of mobile DNA elements concurrently with the separation of the older clades of Afrotheria (∼5.5 pg) and Xenarthra (∼4.5 pg) with larger GS, leaving the Euarchontoglires (∼3.4 pg) and Laurasiatheria (∼2.8 pg) genomes with fewer transposable elements. However, the paucity of GS data (546 mammalian species sized from 5,488 living species) for species, genera, and families calls for caution. Considering that mammalian species may be vanished even before they are known, GS data are sorely needed to phenotype the effects brought about by their variation and to validate any hypotheses on GS evolution in mammals.
Collapse
Affiliation(s)
- C A Redi
- Fondazione IRCCS Policlinico San Matteo, Dipartimento di Biologia e Biotecnologie Lazzaro Spallanzani, Pavia, Italia.
| | | |
Collapse
|
13
|
|
14
|
Sharov AA. Functional Information: Towards Synthesis of Biosemiotics and Cybernetics. ENTROPY (BASEL, SWITZERLAND) 2010; 12:1050-1070. [PMID: 22368439 PMCID: PMC3285384 DOI: 10.3390/e12051050] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Biosemiotics and cybernetics are closely related, yet they are separated by the boundary between life and non-life: biosemiotics is focused on living organisms, whereas cybernetics is applied mostly to non-living artificial devices. However, both classes of systems are agents that perform functions necessary for reaching their goals. I propose to shift the focus of biosemiotics from living organisms to agents in general, which all belong to a pragmasphere or functional universe. Agents should be considered in the context of their hierarchy and origin because their semiosis can be inherited or induced by higher-level agents. To preserve and disseminate their functions, agents use functional information - a set of signs that encode and control their functions. It includes stable memory signs, transient messengers, and natural signs. The origin and evolution of functional information is discussed in terms of transitions between vegetative, animal, and social levels of semiosis, defined by Kull. Vegetative semiosis differs substantially from higher levels of semiosis, because signs are recognized and interpreted via direct code-based matching and are not associated with ideal representations of objects. Thus, I consider a separate classification of signs at the vegetative level that includes proto-icons, proto-indexes, and proto-symbols. Animal and social semiosis are based on classification, and modeling of objects, which represent the knowledge of agents about their body (Innenwelt) and environment (Umwelt).
Collapse
Affiliation(s)
- Alexei A. Sharov
- National Institute on Aging, 251 Bayview Boulevard, Baltimore, MD 21224, USA
| |
Collapse
|
15
|
Li DJ, Zhang S. The Cambrian explosion triggered by critical turning point in genome size evolution. Biochem Biophys Res Commun 2010; 392:240-5. [DOI: 10.1016/j.bbrc.2010.01.032] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2009] [Accepted: 01/08/2010] [Indexed: 11/26/2022]
|
16
|
Sharov AA. Coenzyme autocatalytic network on the surface of oil microspheres as a model for the origin of life. Int J Mol Sci 2009; 10:1838-1852. [PMID: 19468342 PMCID: PMC2680650 DOI: 10.3390/ijms10041838] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2009] [Revised: 04/14/2009] [Accepted: 04/16/2009] [Indexed: 11/16/2022] Open
Abstract
Coenzymes are often considered as remnants of primordial metabolism, but not as hereditary molecules. I suggest that coenzyme-like molecules (CLMs) performed hereditary functions before the emergence of nucleic acids. Autocatalytic CLMs modified (encoded) surface properties of hydrocarbon microspheres, to which they were anchored, and these changes enhanced autocatalysis and propagation of CLMs. Heredity started from a single kind of self-reproducing CLM, and then evolved into more complex coenzyme autocatalytic networks containing multiple kinds of CLMs. Polymerization of CLMs on the surface of microspheres and development of template-based synthesis is a potential evolutionary path towards the emergence of nucleic acids.
Collapse
Affiliation(s)
- Alexei A. Sharov
- Genetics Laboratory, National Institute on Aging, NIA/NIH / 251 Bayview Boulevard, Baltimore, MD 21224, USA; E-Mail:
; Tel. +1-410-558-8556; Fax: +1-410-558-8331
| |
Collapse
|
17
|
Fani R, Fondi M. Origin and evolution of metabolic pathways. Phys Life Rev 2009; 6:23-52. [PMID: 20416849 DOI: 10.1016/j.plrev.2008.12.003] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2008] [Revised: 11/27/2008] [Accepted: 12/01/2008] [Indexed: 10/21/2022]
Abstract
The emergence and evolution of metabolic pathways represented a crucial step in molecular and cellular evolution. In fact, the exhaustion of the prebiotic supply of amino acids and other compounds that were likely present in the ancestral environment, imposed an important selective pressure, favoring those primordial heterotrophic cells which became capable of synthesizing those molecules. Thus, the emergence of metabolic pathways allowed primitive organisms to become increasingly less-dependent on exogenous sources of organic compounds. Comparative analyses of genes and genomes from organisms belonging to Archaea, Bacteria and Eukarya revealed that, during evolution, different forces and molecular mechanisms might have driven the shaping of genomes and the arisal of new metabolic abilities. Among these gene elongations, gene and operon duplications undoubtedly played a major role since they can lead to the (immediate) appearance of new genetic material that, in turn, might undergo evolutionary divergence giving rise to new genes coding for new metabolic abilities. Gene duplication has been invoked in the different schemes proposed to explain why and how the extant metabolic pathways have arisen and shaped. Both the analysis of completely sequenced genomes and directed evolution experiments strongly support one of them, i.e. the patchwork hypothesis, according to which metabolic pathways have been assembled through the recruitment of primitive enzymes that could react with a wide range of chemically related substrates. However, the analysis of the structure and organization of genes belonging to ancient metabolic pathways, such as histidine biosynthesis and nitrogen fixation, suggested that other different hypothesis, i.e. the retrograde hypothesis or the semi-enzymatic theory, may account for the arisal of some metabolic routes.
Collapse
Affiliation(s)
- Renato Fani
- Laboratory of Microbial and Molecular Evolution, Department of Evolutionary Biology, Via Romana 17-19, University of Florence, Italy
| | | |
Collapse
|
18
|
|