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Doré H, Eisenberg AR, Junkins EN, Leventhal GE, Ganesh A, Cordero OX, Paul BG, Valentine DL, O’Malley MA, Wilbanks EG. Targeted hypermutation of putative antigen sensors in multicellular bacteria. Proc Natl Acad Sci U S A 2024; 121:e2316469121. [PMID: 38354254 PMCID: PMC10907252 DOI: 10.1073/pnas.2316469121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2023] [Accepted: 01/10/2024] [Indexed: 02/16/2024] Open
Abstract
Diversity-generating retroelements (DGRs) are used by bacteria, archaea, and viruses as a targeted mutagenesis tool. Through error-prone reverse transcription, DGRs introduce random mutations at specific genomic loci, enabling rapid evolution of these targeted genes. However, the function and benefits of DGR-diversified proteins in cellular hosts remain elusive. We find that 82% of DGRs from one of the major monophyletic lineages of DGR reverse transcriptases are encoded by multicellular bacteria, which often have two or more DGR loci in their genomes. Using the multicellular purple sulfur bacterium Thiohalocapsa sp. PB-PSB1 as an example, we characterized nine distinct DGR loci capable of generating 10282 different combinations of target proteins. With environmental metagenomes from individual Thiohalocapsa aggregates, we show that most of PB-PSB1's DGR target genes are diversified across its biogeographic range, with spatial heterogeneity in the diversity of each locus. In Thiohalocapsa PB-PSB1 and other bacteria hosting this lineage of cellular DGRs, the diversified target genes are associated with NACHT-domain anti-phage defenses and putative ternary conflict systems previously shown to be enriched in multicellular bacteria. We propose that these DGR-diversified targets act as antigen sensors that confer a form of adaptive immunity to their multicellular consortia, though this remains to be experimentally tested. These findings could have implications for understanding the evolution of multicellularity, as the NACHT-domain anti-phage systems and ternary systems share both domain homology and conceptual similarities with the innate immune and programmed cell death pathways of plants and metazoans.
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Affiliation(s)
- H. Doré
- Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, CA93106
| | - A. R. Eisenberg
- Department of Chemical Engineering, University of California, Santa Barbara, CA93106
| | - E. N. Junkins
- Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, CA93106
| | - G. E. Leventhal
- Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, MA02139
| | - Anakha Ganesh
- Bay Paul Center, Marine Biological Laboratory, Woods Hole, MA02543
| | - O. X. Cordero
- Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, MA02139
| | - B. G. Paul
- Bay Paul Center, Marine Biological Laboratory, Woods Hole, MA02543
| | - D. L. Valentine
- Department of Earth Science, University of California, Santa Barbara, CA93106
- Marine Science Institute, University of California, Santa Barbara, CA93106
| | - M. A. O’Malley
- Department of Chemical Engineering, University of California, Santa Barbara, CA93106
- Department of Bioengineering, University of California, Santa Barbara, CA93106
| | - E. G. Wilbanks
- Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, CA93106
- Department of Bioengineering, University of California, Santa Barbara, CA93106
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Arkhipova IR, Yushenova IA. To Be Mobile or Not: The Variety of Reverse Transcriptases and Their Recruitment by Host Genomes. BIOCHEMISTRY. BIOKHIMIIA 2023; 88:1754-1762. [PMID: 38105196 DOI: 10.1134/s000629792311007x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2023] [Revised: 09/18/2023] [Accepted: 09/20/2023] [Indexed: 12/19/2023]
Abstract
Reverse transcriptases (RT), or RNA-dependent DNA polymerases, are unorthodox enzymes that originally added a new angle to the conventional view of the unidirectional flow of genetic information in the cell from DNA to RNA to protein. First discovered in vertebrate retroviruses, RTs were since re-discovered in most eukaryotes, bacteria, and archaea, spanning essentially all domains of life. For retroviruses, RTs provide the ability to copy the RNA genome into DNA for subsequent incorporation into the host genome, which is essential for their replication and survival. In cellular organisms, most RT sequences originate from retrotransposons, the type of self-replicating genetic elements that rely on reverse transcription to copy and paste their sequences into new genomic locations. Some retroelements, however, can undergo domestication, eventually becoming a valuable addition to the overall repertoire of cellular enzymes. They can be beneficial yet accessory, like the diversity-generating elements, or even essential, like the telomerase reverse transcriptases. Nowadays, ever-increasing numbers of domesticated RT-carrying genetic elements are being discovered. It may be argued that domesticated RTs and reverse transcription in general is more widespread in cellular organisms than previously thought, and that many important cellular functions, such as chromosome end maintenance, may evolve from an originally selfish process of converting RNA into DNA.
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Affiliation(s)
- Irina R Arkhipova
- Josephine Bay Paul Center for Comparative Molecular Biology and Evolution, Marine Biological Laboratory, Woods Hole, MA 02543, USA.
| | - Irina A Yushenova
- Josephine Bay Paul Center for Comparative Molecular Biology and Evolution, Marine Biological Laboratory, Woods Hole, MA 02543, USA.
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Webb EA, Held NA, Zhao Y, Graham ED, Conover AE, Semones J, Lee MD, Feng Y, Fu FX, Saito MA, Hutchins DA. Importance of mobile genetic element immunity in numerically abundant Trichodesmium clades. ISME COMMUNICATIONS 2023; 3:15. [PMID: 36823453 PMCID: PMC9950141 DOI: 10.1038/s43705-023-00214-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/15/2022] [Revised: 12/13/2022] [Accepted: 01/12/2023] [Indexed: 02/25/2023]
Abstract
The colony-forming cyanobacteria Trichodesmium spp. are considered one of the most important nitrogen-fixing genera in the warm, low nutrient ocean. Despite this central biogeochemical role, many questions about their evolution, physiology, and trophic interactions remain unanswered. To address these questions, we describe Trichodesmium pangenomic potential via significantly improved genomic assemblies from two isolates and 15 new >50% complete Trichodesmium metagenome-assembled genomes from hand-picked, Trichodesmium colonies spanning the Atlantic Ocean. Phylogenomics identified ~four N2 fixing clades of Trichodesmium across the transect, with T. thiebautii dominating the colony-specific reads. Pangenomic analyses showed that all T. thiebautii MAGs are enriched in COG defense mechanisms and encode a vertically inherited Type III-B Clustered Regularly Interspaced Short Palindromic Repeats and associated protein-based immunity system (CRISPR-Cas). Surprisingly, this CRISPR-Cas system was absent in all T. erythraeum genomes, vertically inherited by T. thiebautii, and correlated with increased signatures of horizontal gene transfer. Additionally, the system was expressed in metaproteomic and transcriptomic datasets and CRISPR spacer sequences with 100% identical hits to field-assembled, putative phage genome fragments were identified. While the currently CO2-limited T. erythraeum is expected to be a 'winner' of anthropogenic climate change, their genomic dearth of known phage resistance mechanisms, compared to T. thiebautii, could put this outcome in question. Thus, the clear demarcation of T. thiebautii maintaining CRISPR-Cas systems, while T. erythraeum does not, identifies Trichodesmium as an ecologically important CRISPR-Cas model system, and highlights the need for more research on phage-Trichodesmium interactions.
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Affiliation(s)
- Eric A Webb
- Marine and Environmental Biology, Department of Biological Sciences, University of Southern California, Los Angeles, CA, 90089, USA.
| | - Noelle A Held
- Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA, 02543, USA
- Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
- Department of Environmental Systems Science, ETH, Zurich, Switzerland
| | - Yiming Zhao
- Marine and Environmental Biology, Department of Biological Sciences, University of Southern California, Los Angeles, CA, 90089, USA
| | - Elaina D Graham
- Marine and Environmental Biology, Department of Biological Sciences, University of Southern California, Los Angeles, CA, 90089, USA
| | - Asa E Conover
- Marine and Environmental Biology, Department of Biological Sciences, University of Southern California, Los Angeles, CA, 90089, USA
| | - Jake Semones
- Marine and Environmental Biology, Department of Biological Sciences, University of Southern California, Los Angeles, CA, 90089, USA
| | - Michael D Lee
- Blue Marble Space Institute of Science, NASA Ames Research Center, Mountain View, CA, 94035, USA
| | - Yuanyuan Feng
- College of Marine and Environmental Sciences, Tianjin University of Science and Technology, Tianjin, 300457, China
| | - Fei-Xue Fu
- Marine and Environmental Biology, Department of Biological Sciences, University of Southern California, Los Angeles, CA, 90089, USA
| | - Mak A Saito
- Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA, 02543, USA
| | - David A Hutchins
- Marine and Environmental Biology, Department of Biological Sciences, University of Southern California, Los Angeles, CA, 90089, USA
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Macadangdang BR, Makanani SK, Miller JF. Accelerated Evolution by Diversity-Generating Retroelements. Annu Rev Microbiol 2022; 76:389-411. [PMID: 35650669 DOI: 10.1146/annurev-micro-030322-040423] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Diversity-generating retroelements (DGRs) create vast amounts of targeted, functional diversity by facilitating the rapid evolution of ligand-binding protein domains. Thousands of DGRs have been identified in bacteria, archaea, and their respective viruses. They are broadly distributed throughout the microbial world, with enrichment observed in certain taxa and environments. The diversification machinery works through a novel mechanism termed mutagenic retrohoming, whereby nucleotide sequence information is copied from an invariant DNA template repeat (TR) into an RNA intermediate, selectively mutagenized at TR adenines during cDNA synthesis by a DGR-encoded reverse transcriptase, and transferred to a variable repeat (VR) region within a variable-protein gene (54). This unidirectional flow of information leaves TR-DNA sequences unmodified, allowing for repeated rounds of mutagenic retrohoming to optimize variable-protein function. DGR target genes are often modular and can encode one or more of a wide variety of discrete functional domains appended to a diversifiable ligand-binding motif. Bacterial variable proteins often localize to cell surfaces, although a subset appear to be cytoplasmic, while phage-encoded DGRs commonly diversify tail fiber-associated receptor-binding proteins. Here, we provide a comprehensive review of the mechanism and consequences of accelerated protein evolution by these unique and beneficial genetic elements. Expected final online publication date for the Annual Review of Microbiology, Volume 76 is September 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
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Affiliation(s)
- Benjamin R Macadangdang
- Division of Neonatology and Developmental Biology, Department of Pediatrics, David Geffen School of Medicine, University of California, Los Angeles, California, USA; .,California NanoSystems Institute, University of California, Los Angeles, California, USA
| | - Sara K Makanani
- California NanoSystems Institute, University of California, Los Angeles, California, USA.,Department of Ecology and Evolutionary Biology, University of California, Los Angeles, California, USA; .,Department of Microbiology, Immunology and Molecular Genetics, David Geffen School of Medicine, University of California, Los Angeles, California, USA;
| | - Jeff F Miller
- California NanoSystems Institute, University of California, Los Angeles, California, USA.,Department of Microbiology, Immunology and Molecular Genetics, David Geffen School of Medicine, University of California, Los Angeles, California, USA; .,Molecular Biology Institute, University of California, Los Angeles, California, USA
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