1
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McCutcheon JP, Garber AI, Spencer N, Warren JM. How do bacterial endosymbionts work with so few genes? PLoS Biol 2024; 22:e3002577. [PMID: 38626194 PMCID: PMC11020763 DOI: 10.1371/journal.pbio.3002577] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/18/2024] Open
Abstract
The move from a free-living environment to a long-term residence inside a host eukaryotic cell has profound effects on bacterial function. While endosymbioses are found in many eukaryotes, from protists to plants to animals, the bacteria that form these host-beneficial relationships are even more diverse. Endosymbiont genomes can become radically smaller than their free-living relatives, and their few remaining genes show extreme compositional biases. The details of how these reduced and divergent gene sets work, and how they interact with their host cell, remain mysterious. This Unsolved Mystery reviews how genome reduction alters endosymbiont biology and highlights a "tipping point" where the loss of the ability to build a cell envelope coincides with a marked erosion of translation-related genes.
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Affiliation(s)
- John P. McCutcheon
- Biodesign Institute and School of Life Sciences, Arizona State University, Tempe, Arizona, United States of America
- Howard Hughes Medical Institute, Chevy Chase, Maryland, United States of America
| | - Arkadiy I. Garber
- Biodesign Institute and School of Life Sciences, Arizona State University, Tempe, Arizona, United States of America
| | - Noah Spencer
- Biodesign Institute and School of Life Sciences, Arizona State University, Tempe, Arizona, United States of America
| | - Jessica M. Warren
- Biodesign Institute and School of Life Sciences, Arizona State University, Tempe, Arizona, United States of America
- Howard Hughes Medical Institute, Chevy Chase, Maryland, United States of America
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2
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Abstract
Animal development is an inherently complex process that is regulated by highly conserved genomic networks, and the resulting phenotype may remain plastic in response to environmental signals. Despite development having been studied in a more natural setting for the past few decades, this framework often precludes the role of microbial prokaryotes in these processes. Here, we address how microbial symbioses impact animal development from the onset of gametogenesis through adulthood. We then provide a first assessment of which developmental processes may or may not be influenced by microbial symbioses and, in doing so, provide a holistic view of the budding discipline of developmental symbiosis.
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Affiliation(s)
- Tyler J Carrier
- GEOMAR Helmholtz Centre for Ocean Research, Kiel 24105, Germany.,Zoological Institute, Christian-Albrechts University of Kiel, Kiel 24118, Germany
| | - Thomas C G Bosch
- Zoological Institute, Christian-Albrechts University of Kiel, Kiel 24118, Germany
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3
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Garzón MJ, Reyes-Prieto M, Gil R. The Minimal Translation Machinery: What We Can Learn From Naturally and Experimentally Reduced Genomes. Front Microbiol 2022; 13:858983. [PMID: 35479634 PMCID: PMC9035817 DOI: 10.3389/fmicb.2022.858983] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Accepted: 03/17/2022] [Indexed: 11/23/2022] Open
Abstract
The current theoretical proposals of minimal genomes have not attempted to outline the essential machinery for proper translation in cells. Here, we present a proposal of a minimal translation machinery based on (1) a comparative analysis of bacterial genomes of insects’ endosymbionts using a machine learning classification algorithm, (2) the empiric genomic information obtained from Mycoplasma mycoides JCVI-syn3.0 the first minimal bacterial genome obtained by design and synthesis, and (3) a detailed functional analysis of the candidate genes based on essentiality according to the DEG database (Escherichia coli and Bacillus subtilis) and the literature. This proposed minimal translational machinery is composed by 142 genes which must be present in any synthetic prokaryotic cell designed for biotechnological purposes, 76.8% of which are shared with JCVI-syn3.0. Eight additional genes were manually included in the proposal for a proper and efficient translation.
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Affiliation(s)
| | - Mariana Reyes-Prieto
- Institute for Integrative Systems Biology, Universitat de València–Consejo Superior de Investigaciones Científicas, Paterna, Spain
- Sequencing and Bioinformatics Service, Foundation for the Promotion of Sanitary and Biomedical Research of the Valencian Community, Valencia, Spain
| | - Rosario Gil
- Departament de Genètica, Universitat de València, Burjassot, Spain
- Institute for Integrative Systems Biology, Universitat de València–Consejo Superior de Investigaciones Científicas, Paterna, Spain
- *Correspondence: Rosario Gil,
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4
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Nicholson D, Salamina M, Panek J, Helena-Bueno K, Brown CR, Hirt RP, Ranson NA, Melnikov SV. Adaptation to genome decay in the structure of the smallest eukaryotic ribosome. Nat Commun 2022; 13:591. [PMID: 35105900 PMCID: PMC8807834 DOI: 10.1038/s41467-022-28281-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Accepted: 01/14/2022] [Indexed: 12/18/2022] Open
Abstract
The evolution of microbial parasites involves the counterplay between natural selection forcing parasites to improve and genetic drifts forcing parasites to lose genes and accumulate deleterious mutations. Here, to understand how this counterplay occurs at the scale of individual macromolecules, we describe cryo-EM structure of ribosomes from Encephalitozoon cuniculi, a eukaryote with one of the smallest genomes in nature. The extreme rRNA reduction in E. cuniculi ribosomes is accompanied with unparalleled structural changes, such as the evolution of previously unknown molten rRNA linkers and bulgeless rRNA. Furthermore, E. cuniculi ribosomes withstand the loss of rRNA and protein segments by evolving an ability to use small molecules as structural mimics of degenerated rRNA and protein segments. Overall, we show that the molecular structures long viewed as reduced, degenerated, and suffering from debilitating mutations possess an array of compensatory mechanisms that allow them to remain active despite the extreme molecular reduction. Many parasitic organisms contain molecular structures that are drastically smaller than analogous structures in non-parasitic organisms. Here the authors describe a cryo-EM structure of the ribosome from E. cuniculi that reveals that it compensated rRNA truncations by evolving the ability to use small molecules as ribosomal building blocks.
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Affiliation(s)
- David Nicholson
- Astbury Centre for Structural Molecular Biology, School of Molecular & Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
| | - Marco Salamina
- Biosciences Institute, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Johan Panek
- Biosciences Institute, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Karla Helena-Bueno
- Biosciences Institute, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Charlotte R Brown
- Biosciences Institute, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Robert P Hirt
- Biosciences Institute, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Neil A Ranson
- Astbury Centre for Structural Molecular Biology, School of Molecular & Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK.
| | - Sergey V Melnikov
- Biosciences Institute, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK. .,Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK.
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5
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Perreau J, Moran NA. Genetic innovations in animal-microbe symbioses. Nat Rev Genet 2021; 23:23-39. [PMID: 34389828 DOI: 10.1038/s41576-021-00395-z] [Citation(s) in RCA: 41] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/28/2021] [Indexed: 02/07/2023]
Abstract
Animal hosts have initiated myriad symbiotic associations with microorganisms and often have maintained these symbioses for millions of years, spanning drastic changes in ecological conditions and lifestyles. The establishment and persistence of these relationships require genetic innovations on the parts of both symbionts and hosts. The nature of symbiont innovations depends on their genetic population structure, categorized here as open, closed or mixed. These categories reflect modes of inter-host transmission that result in distinct genomic features, or genomic syndromes, in symbionts. Although less studied, hosts also innovate in order to preserve and control symbiotic partnerships. New capabilities to sequence host-associated microbial communities and to experimentally manipulate both hosts and symbionts are providing unprecedented insights into how genetic innovations arise under different symbiont population structures and how these innovations function to support symbiotic relationships.
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Affiliation(s)
- Julie Perreau
- Department of Integrative Biology, University of Texas at Austin, Austin, Texas, USA
| | - Nancy A Moran
- Department of Integrative Biology, University of Texas at Austin, Austin, Texas, USA.
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6
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Gupta A, Nair S. Dynamics of Insect-Microbiome Interaction Influence Host and Microbial Symbiont. Front Microbiol 2020; 11:1357. [PMID: 32676060 PMCID: PMC7333248 DOI: 10.3389/fmicb.2020.01357] [Citation(s) in RCA: 85] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2020] [Accepted: 05/27/2020] [Indexed: 12/21/2022] Open
Abstract
Insects share an intimate relationship with their gut microflora and this symbiotic association has developed into an essential evolutionary outcome intended for their survival through extreme environmental conditions. While it has been clearly established that insects, with very few exceptions, associate with several microbes during their life cycle, information regarding several aspects of these associations is yet to be fully unraveled. Acquisition of bacteria by insects marks the onset of microbial symbiosis, which is followed by the adaptation of these bacterial species to the gut environment for prolonged sustenance and successful transmission across generations. Although several insect-microbiome associations have been reported and each with their distinctive features, diversifications and specializations, it is still unclear as to what led to these diversifications. Recent studies have indicated the involvement of various evolutionary processes operating within an insect body that govern the transition of a free-living microbe to an obligate or facultative symbiont and eventually leading to the establishment and diversification of these symbiotic relationships. Data from various studies, summarized in this review, indicate that the symbiotic partners, i.e., the bacteria and the insect undergo several genetic, biochemical and physiological changes that have profound influence on their life cycle and biology. An interesting outcome of the insect-microbe interaction is the compliance of the microbial partner to its eventual genome reduction. Endosymbionts possess a smaller genome as compared to their free-living forms, and thus raising the question what is leading to reductive evolution in the microbial partner. This review attempts to highlight the fate of microbes within an insect body and its implications for both the bacteria and its insect host. While discussion on each specific association would be too voluminous and outside the scope of this review, we present an overview of some recent studies that contribute to a better understanding of the evolutionary trajectory and dynamics of the insect-microbe association and speculate that, in the future, a better understanding of the nature of this interaction could pave the path to a sustainable and environmentally safe way for controlling economically important pests of crop plants.
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Affiliation(s)
| | - Suresh Nair
- Plant-Insect Interaction Group, International Centre for Genetic Engineering and Biotechnology, New Delhi, India
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7
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Narra HP, Sahni A, Walker DH, Sahni SK. Recent research milestones in the pathogenesis of human rickettsioses and opportunities ahead. Future Microbiol 2020; 15:753-765. [PMID: 32691620 PMCID: PMC7787141 DOI: 10.2217/fmb-2019-0266] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2019] [Accepted: 05/14/2020] [Indexed: 12/27/2022] Open
Abstract
Infections caused by pathogenic Rickettsia species continue to scourge human health across the globe. From the point of entry at the site of transmission by arthropod vectors, hematogenous dissemination of rickettsiae occurs to diverse host tissues leading to 'rickettsial vasculitis' as the salient feature of pathogenesis. This perspective article accentuates recent breakthrough developments in the context of host-pathogen-vector interactions during rickettsial infections. The subtopics include potential exploitation of circulating macrophages for spread, identification of new entry mechanisms and regulators of actin-based motility, appreciation of metabolites acquired from and effectors delivered into the host, importance of the toxin-antitoxin module in host-cell interactions, effects of the vector microbiome on rickettsial transmission, and niche-specific riboregulation and adaptation. Further research on these aspects will advance our understanding of the biology of rickettsiae as intracellular pathogens and should enable design and development of new approaches to counter rickettsioses in humans and other hosts.
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Affiliation(s)
- Hema P Narra
- Department of Pathology, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Abha Sahni
- Department of Pathology, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - David H Walker
- Department of Pathology, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Sanjeev K Sahni
- Department of Pathology, University of Texas Medical Branch, Galveston, TX 77555, USA
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8
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Chong RA, Park H, Moran NA. Genome Evolution of the Obligate Endosymbiont Buchnera aphidicola. Mol Biol Evol 2020; 36:1481-1489. [PMID: 30989224 DOI: 10.1093/molbev/msz082] [Citation(s) in RCA: 56] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
An evolutionary consequence of uniparentally transmitted symbiosis is degradation of symbiont genomes. We use the system of aphids and their maternally inherited obligate endosymbiont, Buchnera aphidicola, to explore the evolutionary process of genome degradation. We compared complete genome sequences for 39 Buchnera strains, including 23 newly sequenced symbiont genomes from diverse aphid hosts. We reconstructed the genome of the most recent shared Buchnera ancestor, which contained 616 protein-coding genes, and 39 RNA genes. The extent of subsequent gene loss varied across lineages, resulting in modern genomes ranging from 412 to 646 kb and containing 354-587 protein-coding genes. Loss events were highly nonrandom across loci. Genes involved in replication, transcription, translation, and amino acid biosynthesis are largely retained, whereas genes underlying ornithine biosynthesis, stress responses, and transcriptional regulation were lost repeatedly. Aside from losses, gene order is almost completely stable. The main exceptions involve movement between plasmid and chromosome locations of genes underlying tryptophan and leucine biosynthesis and supporting nutrition of aphid hosts. This set of complete genomes enabled tests for signatures of positive diversifying selection. Of 371 Buchnera genes tested, 29 genes show strong support for ongoing positive selection. These include genes encoding outer membrane porins that are expected to be involved in direct interactions with hosts. Collectively, these results indicate that extensive genome reduction occurred in the ancestral Buchnera prior to aphid diversification and that reduction has continued since, with losses greater in some lineages and for some loci.
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Affiliation(s)
- Rebecca A Chong
- Department of Integrative Biology, University of Texas at Austin, Austin, TX
- Department of Biology, University of Hawaii at Mānoa, Honolulu, HI
| | - Hyunjin Park
- Department of Integrative Biology, University of Texas at Austin, Austin, TX
| | - Nancy A Moran
- Department of Integrative Biology, University of Texas at Austin, Austin, TX
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9
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Coordination of host and symbiont gene expression reveals a metabolic tug-of-war between aphids and Buchnera. Proc Natl Acad Sci U S A 2020; 117:2113-2121. [PMID: 31964845 DOI: 10.1073/pnas.1916748117] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Symbioses between animals and microbes are often described as mutualistic, but are subject to tradeoffs that may manifest as shifts in host and symbiont metabolism, cellular processes, or symbiont density. In pea aphids, the bacterial symbiont Buchnera is confined to specialized aphid cells called bacteriocytes, where it produces essential amino acids needed by hosts. This relationship is dynamic; Buchnera titer varies within individual aphids and among different clonal aphid lineages, and is affected by environmental and host genetic factors. We examined how host genotypic variation relates to host and symbiont function among seven aphid clones differing in Buchnera titer. We found that bacteriocyte gene expression varies among individual aphids and among aphid clones, and that Buchnera gene expression changes in response. By comparing hosts with low and high Buchnera titer, we found that aphids and Buchnera oppositely regulate genes underlying amino acid biosynthesis and cell growth. In high-titer hosts, both bacteriocytes and symbionts show elevated expression of genes underlying energy metabolism. Several eukaryotic cell signaling pathways are differentially expressed in bacteriocytes of low- versus high-titer hosts: Cell-growth pathways are up-regulated in low-titer genotypes, while membrane trafficking, lysosomal processes, and mechanistic target of rapamycin (mTOR) and cytokine pathways are up-regulated in high-titer genotypes. Specific Buchnera functions are up-regulated within different bacteriocyte environments, with genes underlying flagellar body secretion and flagellar assembly overexpressed in low- and high-titer hosts, respectively. Overall, our results reveal allowances and demands made by both host and symbiont engaged in a metabolic "tug-of-war."
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10
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Abstract
Bacteria participate in a wide diversity of symbiotic associations with eukaryotic hosts that require precise interactions for bacterial recognition and persistence. Most commonly, host-associated bacteria interfere with host gene expression to modulate the immune response to the infection. However, many of these bacteria also interfere with host cellular differentiation pathways to create a hospitable niche, resulting in the formation of novel cell types, tissues, and organs. In both of these situations, bacterial symbionts must interact with eukaryotic regulatory pathways. Here, we detail what is known about how bacterial symbionts, from pathogens to mutualists, control host cellular differentiation across the central dogma, from epigenetic chromatin modifications, to transcription and mRNA processing, to translation and protein modifications. We identify four main trends from this survey. First, mechanisms for controlling host gene expression appear to evolve from symbionts co-opting cross-talk between host signaling pathways. Second, symbiont regulatory capacity is constrained by the processes that drive reductive genome evolution in host-associated bacteria. Third, the regulatory mechanisms symbionts exhibit correlate with the cost/benefit nature of the association. And, fourth, symbiont mechanisms for interacting with host genetic regulatory elements are not bound by native bacterial capabilities. Using this knowledge, we explore how the ubiquitous intracellular Wolbachia symbiont of arthropods and nematodes may modulate host cellular differentiation to manipulate host reproduction. Our survey of the literature on how infection alters gene expression in Wolbachia and its hosts revealed that, despite their intermediate-sized genomes, different strains appear capable of a wide diversity of regulatory manipulations. Given this and Wolbachia's diversity of phenotypes and eukaryotic-like proteins, we expect that many symbiont-induced host differentiation mechanisms will be discovered in this system.
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Affiliation(s)
- Shelbi L Russell
- Department of Molecular Cell and Developmental Biology, University of California, Santa Cruz, CA, USA.
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11
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Thairu MW, Hansen AK. It's a small, small world: unravelling the role and evolution of small RNAs in organelle and endosymbiont genomes. FEMS Microbiol Lett 2019; 366:5371121. [PMID: 30844054 DOI: 10.1093/femsle/fnz049] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2018] [Accepted: 03/05/2019] [Indexed: 12/19/2022] Open
Abstract
Organelles and host-restricted bacterial symbionts are characterized by having highly reduced genomes that lack many key regulatory genes and elements. Thus, it has been hypothesized that the eukaryotic nuclear genome is primarily responsible for regulating these symbioses. However, with the discovery of organelle- and symbiont-expressed small RNAs (sRNAs) there is emerging evidence that these sRNAs may play a role in gene regulation as well. Here, we compare the diversity of organelle and bacterial symbiont sRNAs recently identified using genome-enabled '-omic' technologies and discuss their potential role in gene regulation. We also discuss how the genome architecture of small genomes may influence the evolution of these sRNAs and their potential function. Additionally, these new studies suggest that some sRNAs are conserved within organelle and symbiont taxa and respond to changes in the environment and/or their hosts. In summary, these results suggest that organelle and symbiont sRNAs may play a role in gene regulation in addition to nuclear-encoded host mechanisms.
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Affiliation(s)
- Margaret W Thairu
- Department of Entomology, University of California, Riverside, Riverside, CA, USA
| | - Allison K Hansen
- Department of Entomology, University of California, Riverside, Riverside, CA, USA
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12
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Thairu MW, Hansen AK. Changes in Aphid Host Plant Diet Influence the Small-RNA Expression Profiles of Its Obligate Nutritional Symbiont, Buchnera. mBio 2019; 10:e01733-19. [PMID: 31744912 PMCID: PMC6867890 DOI: 10.1128/mbio.01733-19] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2019] [Accepted: 10/08/2019] [Indexed: 12/31/2022] Open
Abstract
Plants are a difficult food resource to use, and herbivorous insects have evolved a variety of mechanisms that allow them to fully exploit this poor nutritional resource. One such mechanism is the maintenance of bacterial symbionts that aid in host plant feeding and development. The majority of these intracellular symbionts have highly eroded genomes that lack many key regulatory genes; consequently, it is unclear if these symbionts can respond to changes in the insect's diet to facilitate host plant use. There is emerging evidence that symbionts with highly eroded genomes express small RNAs (sRNAs), some of which potentially regulate gene expression. In this study, we sought to determine if the reduced genome of the nutritional symbiont (Buchnera) in the pea aphid responds to changes in the aphid's host plant diet. Using transcriptome sequencing (RNA-seq), Buchnera sRNA expression profiles were characterized within two Buchnera life stages when pea aphids fed on either alfalfa or fava bean. Overall, this study demonstrates that Buchnera sRNA expression changes not only with life stage but also with changes in aphid host plant diet. Of the 321 sRNAs characterized in this study, 47% were previously identified and 22% showed evidence of conservation in two or more Buchnera taxa. Functionally, 13 differentially expressed sRNAs were predicted to target genes related to pathways involved in essential amino acid biosynthesis. Overall, results from this study reveal that host plant diet influences the expression of conserved and lineage-specific sRNAs in Buchnera and that these sRNAs display distinct host plant-specific expression profiles among biological replicates.IMPORTANCE In general, the genomes of intracellular bacterial symbionts are reduced compared to those of free-living relatives and lack many key regulatory genes. Many of these reduced genomes belong to obligate mutualists of insects that feed on a diet that is deficient in essential nutrients, such as essential amino acids. It is unclear if these symbionts respond with their host to changes in insect diet, because of their reduced regulatory capacity. Emerging evidence suggests that these symbionts express small RNAs (sRNAs) that regulate gene expression at the posttranscriptional level. Therefore, in this study, we sought to determine if the reduced genome of the nutritional symbiont Buchnera in the pea aphid responds to changes in the aphid's host plant diet. This study demonstrates for the first time that Buchnera sRNAs, some conserved in two or more Buchnera lineages, are differentially expressed when aphids feed on different plant species and potentially target genes within essential amino acid biosynthesis pathways.
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Affiliation(s)
- Margaret W Thairu
- Department of Entomology, University of California, Riverside, Riverside, California, USA
- Department of Bacteriology, University of Wisconsin, Madison, Madison, Wisconsin, USA
| | - Allison K Hansen
- Department of Entomology, University of California, Riverside, Riverside, California, USA
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13
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Wang Y, Zhu FC, He LS, Danchin A. Unique tRNA gene profile suggests paucity of nucleotide modifications in anticodons of a deep-sea symbiotic Spiroplasma. Nucleic Acids Res 2019; 46:2197-2203. [PMID: 29390076 PMCID: PMC5861454 DOI: 10.1093/nar/gky045] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2017] [Accepted: 01/18/2018] [Indexed: 12/22/2022] Open
Abstract
The position 34 of a tRNA is always modified for efficient recognition of codons and accurate integration of amino acids by the translation machinery. Here, we report genomics features of a deep-sea gut symbiotic Spiroplasma, which suggests that the organism does not require tRNA(34) anticodon modifications. In the genome, there is a novel set of tRNA genes composed of 32 species for recognition of the 20 amino acids. Among the anticodons of the tRNAs, we witnessed the presence of both U34- and C34-containing tRNAs required to decode NNR (A/G) 2:2 codons as countermeasure of probable loss of anticodon modification genes. In the tRNA fragments detected in the gut transcriptome, mismatches expected to be caused by some tRNA modifications were not shown in their alignments with the corresponding genes. However, the probable paucity of modified anticodons did not fundamentally change the codon usage pattern of the Spiroplasma. The tRNA gene profile that probably resulted from the paucity of tRNA(34) modifications was not observed in other symbionts and deep-sea bacteria, indicating that this phenomenon was an evolutionary dead-end. This study provides insights on co-evolution of translation machine and tRNA genes and steric constraints of codon-anticodon interactions in deep-sea extreme environment.
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Affiliation(s)
- Yong Wang
- Institute of Deep-Sea Science and Engineering, Chinese Academy of Sciences, Sanya, Hainan, China
| | - Fang-Chao Zhu
- Institute of Deep-Sea Science and Engineering, Chinese Academy of Sciences, Sanya, Hainan, China
| | - Li-Sheng He
- Institute of Deep-Sea Science and Engineering, Chinese Academy of Sciences, Sanya, Hainan, China
| | - Antoine Danchin
- Institute of Cardiometabolism and Nutrition, Hôpital de la Pitié-Salpêtrière, 47 boulevard de l'Hôpital, 75013 Paris, France.,School of Biomedical Sciences, Li Kashing Faculty of Medicine, University of Hong Kong, 21 Sassoon Road, SAR Hong Kong, China
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14
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Cicada Endosymbionts Have tRNAs That Are Correctly Processed Despite Having Genomes That Do Not Encode All of the tRNA Processing Machinery. mBio 2019; 10:mBio.01950-18. [PMID: 31213566 PMCID: PMC6581868 DOI: 10.1128/mbio.01950-18] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The smallest bacterial genomes, in the range of about 0.1 to 0.5 million base pairs, are commonly found in the nutritional endosymbionts of insects. These tiny genomes are missing genes that encode proteins and RNAs required for the translation of mRNAs, one of the most highly conserved and important cellular processes. In this study, we found that the bacterial endosymbionts of cicadas have genomes which encode incomplete tRNA sets and lack genes required for tRNA processing. Nevertheless, we found that endosymbiont tRNAs are correctly processed at their 5′ and 3′ ends and, surprisingly, that mostly exist as tRNA halves. We hypothesize that the cicada host must supply its symbionts with these missing tRNA processing activities. Gene loss and genome reduction are defining characteristics of endosymbiotic bacteria. The most highly reduced endosymbiont genomes have lost numerous essential genes related to core cellular processes such as replication, transcription, and translation. Computational gene predictions performed for the genomes of the two bacterial symbionts of the cicada Diceroprocta semicincta, “Candidatus Hodgkinia cicadicola” (Alphaproteobacteria) and “Ca. Sulcia muelleri” (Bacteroidetes), have found only 26 and 16 tRNA genes and 15 and 10 aminoacyl tRNA synthetase genes, respectively. Furthermore, the original “Ca. Hodgkinia cicadicola” genome annotation was missing several essential genes involved in tRNA processing, such as those encoding RNase P and CCA tRNA nucleotidyltransferase as well as several RNA editing enzymes required for tRNA maturation. How these cicada endosymbionts perform basic translation-related processes remains unknown. Here, by sequencing eukaryotic mRNAs and total small RNAs, we show that the limited tRNA set predicted by computational annotation of “Ca. Sulcia muelleri” and “Ca. Hodgkinia cicadicola” is likely correct. Furthermore, we show that despite the absence of genes encoding tRNA processing activities in the symbiont genomes, symbiont tRNAs have correctly processed 5′ and 3′ ends and seem to undergo nucleotide modification. Surprisingly, we found that most “Ca. Hodgkinia cicadicola” and “Ca. Sulcia muelleri” tRNAs exist as tRNA halves. We hypothesize that “Ca. Sulcia muelleri” and “Ca. Hodgkinia cicadicola” tRNAs function in bacterial translation but require host-encoded enzymes to do so.
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15
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Thairu MW, Cheng S, Hansen AK. A sRNA in a reduced mutualistic symbiont genome regulates its own gene expression. Mol Ecol 2017; 27:1766-1776. [PMID: 29134727 DOI: 10.1111/mec.14424] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2017] [Revised: 10/29/2017] [Accepted: 10/31/2017] [Indexed: 01/10/2023]
Abstract
Similar to other nutritional endosymbionts that are obligate for host survival, the mutualistic aphid endosymbiont, Buchnera, has a highly reduced genome with few regulatory elements. Until recently, it was thought that aphid hosts were primarily responsible for regulating their symbiotic relationship. However, we recently revealed that Buchnera displays differential protein regulation, but not mRNA expression. We also identified a number of conserved small RNAs (sRNAs) that are expressed among Buchnera taxa. In this study, we investigate whether differential protein regulation in Buchnera is the result of post-transcriptional gene regulation via sRNAs. We characterize the sRNA profile of two Buchnera life stages: (i) when Buchnera is transitioning from an extracellular proliferating state in aphid embryos and (ii) when Buchnera is in an intracellular nonproliferating state in aphid bacteriocytes (specialized symbiont cells). Overall, we identified 90 differentially expressed sRNAs, 97% of which were upregulated in aphid embryos. Of these sRNAs, the majority were predicted to be involved in the regulation of various metabolic processes, including arginine biosynthesis. Using a heterologous dual expression vector, we reveal for the first time that a Buchnera antisense sRNA can post-transcriptionally interact with its cognate Buchnera coding sequence, carB, a gene involved in arginine biosynthesis. These results corroborate our in vivo RNAseq and proteomic data, where the candidate antisense sRNA carB and the protein CarB are significantly upregulated in aphid embryos. Overall, we demonstrate that Buchnera may regulate gene expression independently from its host by utilizing sRNAs.
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Affiliation(s)
- Margaret W Thairu
- Department of Entomology, University of Illinois, Urbana-Champaign, Urbana, IL, USA.,Department of Entomology, University of California Riverside, Riverside, CA, USA
| | - Siyuan Cheng
- Department of Entomology, University of Illinois, Urbana-Champaign, Urbana, IL, USA.,Program in Biological and Biomedical Sciences, Yale University, New Haven, CT, USA
| | - Allison K Hansen
- Department of Entomology, University of Illinois, Urbana-Champaign, Urbana, IL, USA.,Department of Entomology, University of California Riverside, Riverside, CA, USA
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16
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Thairu MW, Skidmore IH, Bansal R, Nováková E, Hansen TE, Li-Byarlay H, Wickline SA, Hansen AK. Efficacy of RNA interference knockdown using aerosolized short interfering RNAs bound to nanoparticles in three diverse aphid species. INSECT MOLECULAR BIOLOGY 2017; 26:356-368. [PMID: 28314050 DOI: 10.1111/imb.12301] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
RNA interference (RNAi) has emerged as a promising method for validating gene function; however, its utility in nonmodel insects has proven problematic, with delivery methods being one of the main obstacles. This study investigates a novel method of RNAi delivery in aphids, the aerosolization of short interfering RNA (siRNA)-nanoparticle complexes. By using nanoparticles as a siRNA carrier, the likelihood of cellular uptake is increased, when compared to methods previously used in insects. To determine the efficacy of this RNAi delivery system, siRNAs were aerosolized with and without nanoparticles in three aphid species: Acyrthosiphon pisum, Aphis glycines and Schizaphis graminum. The genes targeted for knockdown were carotene dehydrogenase (tor), which is important for pigmentation in Ac. pisum, and branched chain-amino acid transaminase (bcat), which is essential in the metabolism of branched-chain amino acids in all three aphid species. Overall, we observed modest gene knockdown of tor in Ac. pisum and moderate gene knockdown of bcat in Ap. glycines along with its associated phenotype. We also determined that the nanoparticle emulsion significantly increased the efficacy of gene knockdown. Overall, these results suggest that the aerosolized siRNA-nanoparticle delivery method is a promising new high-throughput and non-invasive RNAi delivery method in some aphid species.
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Affiliation(s)
- M W Thairu
- Department of Entomology, University of Illinois, Urbana-Champaign, IL, USA
| | - I H Skidmore
- Department of Entomology, University of Illinois, Urbana-Champaign, IL, USA
| | - R Bansal
- Department of Entomology, The Ohio State University, Wooster, OH, USA
| | - E Nováková
- Department of Entomology, University of Illinois, Urbana-Champaign, IL, USA
| | - T E Hansen
- Department of Entomology, University of Illinois, Urbana-Champaign, IL, USA
| | - H Li-Byarlay
- Department of Entomology, North Carolina State University, Raleigh, NC, USA
| | - S A Wickline
- School of Medicine, Washington University in St. Louis, MO, USA
| | - A K Hansen
- Department of Entomology, University of Illinois, Urbana-Champaign, IL, USA
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17
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Mao M, Yang X, Poff K, Bennett G. Comparative Genomics of the Dual-Obligate Symbionts from the Treehopper, Entylia carinata (Hemiptera: Membracidae), Provide Insight into the Origins and Evolution of an Ancient Symbiosis. Genome Biol Evol 2017; 9:1803-1815. [PMID: 28854637 PMCID: PMC5533117 DOI: 10.1093/gbe/evx134] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/08/2017] [Indexed: 12/20/2022] Open
Abstract
Insect species in the Auchenorrhyncha suborder (Hemiptera) maintain ancient obligate symbioses with bacteria that provide essential amino acids (EAAs) deficient in their plant-sap diets. Molecular studies have revealed that two complementary symbiont lineages, "Candidatus Sulcia muelleri" and a betaproteobacterium ("Ca. Zinderia insecticola" in spittlebugs [Cercopoidea] and "Ca. Nasuia deltocephalinicola" in leafhoppers [Cicadellidae]) may have persisted in the suborder since its origin ∼300 Ma. However, investigation of how this pair has co-evolved on a genomic level is limited to only a few host lineages. We sequenced the complete genomes of Sulcia and a betaproteobacterium from the treehopper, Entylia carinata (Membracidae: ENCA), as the first representative from this species-rich group. It also offers the opportunity to compare symbiont evolution across a major insect group, the Membracoidea (leafhoppers + treehoppers). Genomic analyses show that the betaproteobacteria in ENCA is a member of the Nasuia lineage. Both symbionts have larger genomes (Sulcia = 218 kb and Nasuia = 144 kb) than related lineages in Deltocephalinae leafhoppers, retaining genes involved in basic cellular functions and information processing. Nasuia-ENCA further exhibits few unique gene losses, suggesting that its parent lineage in the common ancestor to the Membracoidea was already highly reduced. Sulcia-ENCA has lost the abilities to synthesize menaquinone cofactor and to complete the synthesis of the branched-chain EAAs. Both capabilities are conserved in other Sulcia lineages sequenced from across the Auchenorrhyncha. Finally, metagenomic sequencing recovered the partial genome of an Arsenophonus symbiont, although it infects only 20% of individuals indicating a facultative role.
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Affiliation(s)
- Meng Mao
- Department of Plant and Environmental Protection Sciences, University of Hawaii at Mānoa
| | - Xiushuai Yang
- Department of Plant and Environmental Protection Sciences, University of Hawaii at Mānoa
| | - Kirsten Poff
- Department of Plant and Environmental Protection Sciences, University of Hawaii at Mānoa
| | - Gordon Bennett
- Department of Plant and Environmental Protection Sciences, University of Hawaii at Mānoa
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18
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Ardell DH, Hou YM. Initiator tRNA genes template the 3' CCA end at high frequencies in bacteria. BMC Genomics 2016; 17:1003. [PMID: 27927177 PMCID: PMC5143459 DOI: 10.1186/s12864-016-3314-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2016] [Accepted: 11/18/2016] [Indexed: 01/06/2023] Open
Abstract
Background While the CCA sequence at the mature 3′ end of tRNAs is conserved and critical for translational function, a genetic template for this sequence is not always contained in tRNA genes. In eukaryotes and Archaea, the CCA ends of tRNAs are synthesized post-transcriptionally by CCA-adding enzymes. In Bacteria, tRNA genes template CCA sporadically. Results In order to understand the variation in how prokaryotic tRNA genes template CCA, we re-annotated tRNA genes in tRNAdb-CE database version 0.8. Among 132,129 prokaryotic tRNA genes, initiator tRNA genes template CCA at the highest average frequency (74.1%) over all functional classes except selenocysteine and pyrrolysine tRNA genes (88.1% and 100% respectively). Across bacterial phyla and a wide range of genome sizes, many lineages exist in which predominantly initiator tRNA genes template CCA. Convergent and parallel retention of CCA templating in initiator tRNA genes evolved in independent histories of reductive genome evolution in Bacteria. Also, in a majority of cyanobacterial and actinobacterial genera, predominantly initiator tRNA genes template CCA. We also found that a surprising fraction of archaeal tRNA genes template CCA. Conclusions We suggest that cotranscriptional synthesis of initiator tRNA CCA 3′ ends can complement inefficient processing of initiator tRNA precursors, “bootstrap” rapid initiation of protein synthesis from a non-growing state, or contribute to an increase in cellular growth rates by reducing overheads of mass and energy to maintain nonfunctional tRNA precursor pools. More generally, CCA templating in structurally non-conforming tRNA genes can afford cells robustness and greater plasticity to respond rapidly to environmental changes and stimuli. Electronic supplementary material The online version of this article (doi:10.1186/s12864-016-3314-x) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- David H Ardell
- Program in Quantitative and Systems Biology, University of California, 5200 North Lake Road, CA, 95343, Merced, USA. .,Molecular and Cell Biology Unit, School of Natural Sciences, University of California, 5200 North Lake Road, Merced, CA, 95343, USA.
| | - Ya-Ming Hou
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, 233 South 10th Street, BLSB 220, Philadelphia, PA, 19107, USA
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19
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Kim D, Thairu MW, Hansen AK. Novel Insights into Insect-Microbe Interactions-Role of Epigenomics and Small RNAs. FRONTIERS IN PLANT SCIENCE 2016; 7:1164. [PMID: 27540386 PMCID: PMC4972996 DOI: 10.3389/fpls.2016.01164] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2016] [Accepted: 07/20/2016] [Indexed: 05/23/2023]
Abstract
It has become increasingly clear that microbes form close associations with the vast majority of animal species, especially insects. In fact, an array of diverse microbes is known to form shared metabolic pathways with their insect hosts. A growing area of research in insect-microbe interactions, notably for hemipteran insects and their mutualistic symbionts, is to elucidate the regulation of this inter-domain metabolism. This review examines two new emerging mechanisms of gene regulation and their importance in host-microbe interactions. Specifically, we highlight how the incipient areas of research on regulatory "dark matter" such as epigenomics and small RNAs, can play a pivotal role in the evolution of both insect and microbe gene regulation. We then propose specific models of how these dynamic forms of gene regulation can influence insect-symbiont-plant interactions. Future studies in this area of research will give us a systematic understanding of how these symbiotic microbes and animals reciprocally respond to and regulate their shared metabolic processes.
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20
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Hansen AK, Degnan PH. Widespread expression of conserved small RNAs in small symbiont genomes. THE ISME JOURNAL 2014; 8:2490-502. [PMID: 25012903 PMCID: PMC4260695 DOI: 10.1038/ismej.2014.121] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2014] [Revised: 06/02/2014] [Accepted: 06/05/2014] [Indexed: 12/17/2022]
Abstract
Genome architecture of a microbe markedly changes when it transitions from a free-living lifestyle to an obligate symbiotic association within eukaryotic cells. These symbiont genomes experience numerous rearrangements and massive gene loss, which is expected to radically alter gene regulatory networks compared with those of free-living relatives. As such, it remains unclear whether and how these small symbiont genomes regulate gene expression. Here, using a label-free mass-spec quantification approach we found that differential protein regulation occurs in Buchnera, a model symbiont with a reduced genome, when it transitions between two distinct life stages. However, differential mRNA expression could not be detected between Buchnera life stages, despite the presence of a small number of putative transcriptional regulators. Instead a comparative analysis of small RNA expression profiles among five divergent Buchnera lineages, spanning a variety of Buchnera life stages, reveals 140 novel intergenic and antisense small RNAs and 517 untranslated regions that were significantly expressed, some of which have been conserved for ∼65 million years. In addition, the majority of these small RNAs exhibit both sequence covariation and thermodynamic stability, indicators of a potential structural RNA role. Together, these data suggest that gene regulation at the post-transcriptional level may be important in Buchnera. This is the first study to empirically identify Buchnera small RNAs, and we propose that these novel small RNAs may facilitate post-transcriptional regulation through translational inhibition/activation, and/or transcript stability. Ultimately, post-transcriptional regulation may shape metabolic complementation between Buchnera and its aphid host, thus impacting the animal's ecology and evolution.
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Affiliation(s)
- Allison K Hansen
- Department of Entomology, School of Integrative Biology, University of Illinois at Urbana-Champaign, Urbana, IL, USA
- Department of Ecology and Evolutionary Biology, Microbial Diversity Institute, Yale University, New Haven, CT, USA
| | - Patrick H Degnan
- Department of Microbiology, University of Illinois at Urbana-Champaign, Urbana, IL, USA
- Department of Microbial Pathogenesis, Microbial Diversity Institute, Yale University, New Haven, CT, USA
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21
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Reductive genome evolution at both ends of the bacterial population size spectrum. Nat Rev Microbiol 2014; 12:841-50. [DOI: 10.1038/nrmicro3331] [Citation(s) in RCA: 111] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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22
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Affiliation(s)
- Nancy A. Moran
- Department of Integrative Biology, University of Texas at Austin, Texas 78712; ,
| | - Gordon M. Bennett
- Department of Integrative Biology, University of Texas at Austin, Texas 78712; ,
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23
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Wald N, Margalit H. Auxiliary tRNAs: large-scale analysis of tRNA genes reveals patterns of tRNA repertoire dynamics. Nucleic Acids Res 2014; 42:6552-66. [PMID: 24782525 PMCID: PMC4041420 DOI: 10.1093/nar/gku245] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Decoding of all codons can be achieved by a subset of tRNAs. In bacteria, certain tRNA species are mandatory, while others are auxiliary and are variably used. It is currently unknown how this variability has evolved and whether it provides an adaptive advantage. Here we shed light on the subset of auxiliary tRNAs, using genomic data from 319 bacteria. By reconstructing the evolution of tRNAs we show that the auxiliary tRNAs are highly dynamic, being frequently gained and lost along the phylogenetic tree, with a clear dominance of loss events for most auxiliary tRNA species. We reveal distinct co-gain and co-loss patterns for subsets of the auxiliary tRNAs, suggesting that they are subjected to the same selection forces. Controlling for phylogenetic dependencies, we find that the usage of these tRNA species is positively correlated with GC content and may derive directly from nucleotide bias or from preference of Watson-Crick codon-anticodon interactions. Our results highlight the highly dynamic nature of these tRNAs and their complicated balance with codon usage.
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Affiliation(s)
- Naama Wald
- Department of Microbiology and Molecular Genetics, IMRIC, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem 91120, Israel
| | - Hanah Margalit
- Department of Microbiology and Molecular Genetics, IMRIC, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem 91120, Israel
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