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Johnston IG. The Nitroplast and Its Relatives Support a Universal Model of Features Predicting Gene Retention in Endosymbiont and Organelle Genomes. Genome Biol Evol 2024; 16:evae132. [PMID: 38900924 PMCID: PMC11221429 DOI: 10.1093/gbe/evae132] [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: 04/22/2024] [Revised: 06/03/2024] [Accepted: 06/14/2024] [Indexed: 06/22/2024] Open
Abstract
Endosymbiotic relationships have shaped eukaryotic life. As endosymbionts coevolve with their host, toward full integration as organelles, their genomes tend to shrink, with genes being completely lost or transferred to the host nucleus. Modern endosymbionts and organelles show diverse patterns of gene retention, and why some genes and not others are retained in these genomes is not fully understood. Recent bioinformatic study has explored hypothesized influences on these evolutionary processes, finding that hydrophobicity and amino acid chemistry predict patterns of gene retention, both in organelles across eukaryotes and in less mature endosymbiotic relationships. The exciting ongoing elucidation of endosymbiotic relationships affords an independent set of instances to test this theory. Here, we compare the properties of retained genes in the nitroplast, recently reported to be an integrated organelle, two related cyanobacterial endosymbionts that form "spheroid bodies" in their host cells, and a range of other endosymbionts, with free-living relatives of each. We find that in each case, the symbiont's genome encodes proteins with higher hydrophobicity and lower amino pKa than their free-living relative, supporting the data-derived model predicting the retention propensity of genes across endosymbiont and organelle genomes.
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Affiliation(s)
- Iain G Johnston
- Department of Mathematics, University of Bergen, Bergen, Norway
- Computational Biology Unit, University of Bergen, Bergen, Norway
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2
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Gabr A, Stephens TG, Reinfelder JR, Liau P, Calatrava V, Grossman AR, Bhattacharya D. Evidence of a putative CO 2 delivery system to the chromatophore in the photosynthetic amoeba Paulinella. ENVIRONMENTAL MICROBIOLOGY REPORTS 2024; 16:e13304. [PMID: 38923306 PMCID: PMC11194058 DOI: 10.1111/1758-2229.13304] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2024] [Accepted: 05/22/2024] [Indexed: 06/28/2024]
Abstract
The photosynthetic amoeba, Paulinella provides a recent (ca. 120 Mya) example of primary plastid endosymbiosis. Given the extensive data demonstrating host lineage-driven endosymbiont integration, we analysed nuclear genome and transcriptome data to investigate mechanisms that may have evolved in Paulinella micropora KR01 (hereinafter, KR01) to maintain photosynthetic function in the novel organelle, the chromatophore. The chromatophore is of α-cyanobacterial provenance and has undergone massive gene loss due to Muller's ratchet, but still retains genes that encode the ancestral α-carboxysome and the shell carbonic anhydrase, two critical components of the biophysical CO2 concentrating mechanism (CCM) in cyanobacteria. We identified KR01 nuclear genes potentially involved in the CCM that arose via duplication and divergence and are upregulated in response to high light and downregulated under elevated CO2. We speculate that these genes may comprise a novel CO2 delivery system (i.e., a biochemical CCM) to promote the turnover of the RuBisCO carboxylation reaction and counteract photorespiration. We posit that KR01 has an inefficient photorespiratory system that cannot fully recycle the C2 product of RuBisCO oxygenation back to the Calvin-Benson cycle. Nonetheless, both these systems appear to be sufficient to allow Paulinella to persist in environments dominated by faster-growing phototrophs.
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Affiliation(s)
- Arwa Gabr
- Graduate Program in Molecular Bioscience and Program in Microbiology and Molecular GeneticsRutgers UniversityNew BrunswickNew JerseyUSA
| | - Timothy G. Stephens
- Department of Biochemistry and MicrobiologyRutgers UniversityNew BrunswickNew JerseyUSA
| | - John R. Reinfelder
- Department of Environmental SciencesRutgers UniversityNew BrunswickNew JerseyUSA
| | - Pinky Liau
- Department of Biochemistry and MicrobiologyRutgers UniversityNew BrunswickNew JerseyUSA
| | - Victoria Calatrava
- Department of Plant BiologyThe Carnegie Institution for ScienceStanfordCaliforniaUSA
| | - Arthur R. Grossman
- Department of Plant BiologyThe Carnegie Institution for ScienceStanfordCaliforniaUSA
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3
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Dai GZ, Song WY, Xu HF, Tu M, Yu C, Li ZK, Shang JL, Jin CL, Ding CS, Zuo LZ, Liu YR, Yan WW, Zang SS, Liu K, Zhang Z, Bock R, Qiu BS. Hypothetical chloroplast reading frame 51 encodes a photosystem I assembly factor in cyanobacteria. THE PLANT CELL 2024; 36:1844-1867. [PMID: 38146915 PMCID: PMC11062458 DOI: 10.1093/plcell/koad330] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/06/2023] [Revised: 09/29/2023] [Accepted: 12/20/2023] [Indexed: 12/27/2023]
Abstract
Hypothetical chloroplast open reading frames (ycfs) are putative genes in the plastid genomes of photosynthetic eukaryotes. Many ycfs are also conserved in the genomes of cyanobacteria, the presumptive ancestors of present-day chloroplasts. The functions of many ycfs are still unknown. Here, we generated knock-out mutants for ycf51 (sll1702) in the cyanobacterium Synechocystis sp. PCC 6803. The mutants showed reduced photoautotrophic growth due to impaired electron transport between photosystem II (PSII) and PSI. This phenotype results from greatly reduced PSI content in the ycf51 mutant. The ycf51 disruption had little effect on the transcription of genes encoding photosynthetic complex components and the stabilization of the PSI complex. In vitro and in vivo analyses demonstrated that Ycf51 cooperates with PSI assembly factor Ycf3 to mediate PSI assembly. Furthermore, Ycf51 interacts with the PSI subunit PsaC. Together with its specific localization in the thylakoid membrane and the stromal exposure of its hydrophilic region, our data suggest that Ycf51 is involved in PSI complex assembly. Ycf51 is conserved in all sequenced cyanobacteria, including the earliest branching cyanobacteria of the Gloeobacter genus, and is also present in the plastid genomes of glaucophytes. However, Ycf51 has been lost from other photosynthetic eukaryotic lineages. Thus, Ycf51 is a PSI assembly factor that has been functionally replaced during the evolution of oxygenic photosynthetic eukaryotes.
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Affiliation(s)
- Guo-Zheng Dai
- School of Life Sciences, and Hubei Key Laboratory of Genetic Regulation and Integrative Biology, Central China Normal University, Wuhan 430079, Hubei, PR China
| | - Wei-Yu Song
- School of Life Sciences, and Hubei Key Laboratory of Genetic Regulation and Integrative Biology, Central China Normal University, Wuhan 430079, Hubei, PR China
| | - Hai-Feng Xu
- School of Life Sciences, and Hubei Key Laboratory of Genetic Regulation and Integrative Biology, Central China Normal University, Wuhan 430079, Hubei, PR China
| | - Miao Tu
- School of Life Sciences, and Hubei Key Laboratory of Genetic Regulation and Integrative Biology, Central China Normal University, Wuhan 430079, Hubei, PR China
| | - Chen Yu
- School of Life Sciences, and Hubei Key Laboratory of Genetic Regulation and Integrative Biology, Central China Normal University, Wuhan 430079, Hubei, PR China
| | - Zheng-Ke Li
- School of Life Sciences, and Hubei Key Laboratory of Genetic Regulation and Integrative Biology, Central China Normal University, Wuhan 430079, Hubei, PR China
| | - Jin-Long Shang
- School of Life Sciences, and Hubei Key Laboratory of Genetic Regulation and Integrative Biology, Central China Normal University, Wuhan 430079, Hubei, PR China
| | - Chun-Lei Jin
- School of Life Sciences, and Hubei Key Laboratory of Genetic Regulation and Integrative Biology, Central China Normal University, Wuhan 430079, Hubei, PR China
| | - Chao-Shun Ding
- School of Life Sciences, and Hubei Key Laboratory of Genetic Regulation and Integrative Biology, Central China Normal University, Wuhan 430079, Hubei, PR China
| | - Ling-Zi Zuo
- School of Life Sciences, and Hubei Key Laboratory of Genetic Regulation and Integrative Biology, Central China Normal University, Wuhan 430079, Hubei, PR China
| | - Yan-Ru Liu
- School of Life Sciences, and Hubei Key Laboratory of Genetic Regulation and Integrative Biology, Central China Normal University, Wuhan 430079, Hubei, PR China
| | - Wei-Wei Yan
- School of Life Sciences, and Hubei Key Laboratory of Genetic Regulation and Integrative Biology, Central China Normal University, Wuhan 430079, Hubei, PR China
| | - Sha-Sha Zang
- School of Life Sciences, and Hubei Key Laboratory of Genetic Regulation and Integrative Biology, Central China Normal University, Wuhan 430079, Hubei, PR China
| | - Ke Liu
- School of Life Sciences, and Hubei Key Laboratory of Genetic Regulation and Integrative Biology, Central China Normal University, Wuhan 430079, Hubei, PR China
| | - Zheng Zhang
- School of Life Sciences, and Hubei Key Laboratory of Genetic Regulation and Integrative Biology, Central China Normal University, Wuhan 430079, Hubei, PR China
| | - Ralph Bock
- Department III, Max-Planck-Institut für Molekulare Pflanzenphysiologie, D-14476 Potsdam-Golm, Germany
| | - Bao-Sheng Qiu
- School of Life Sciences, and Hubei Key Laboratory of Genetic Regulation and Integrative Biology, Central China Normal University, Wuhan 430079, Hubei, PR China
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4
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Liu SJ, Lin GM, Yuan YQ, Chen W, Zhang JY, Zhang CC. A conserved protein inhibitor brings under check the activity of RNase E in cyanobacteria. Nucleic Acids Res 2024; 52:404-419. [PMID: 38000383 PMCID: PMC10783494 DOI: 10.1093/nar/gkad1094] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2023] [Revised: 09/21/2023] [Accepted: 10/31/2023] [Indexed: 11/26/2023] Open
Abstract
The bacterial ribonuclease RNase E plays a key role in RNA metabolism. Yet, with a large substrate spectrum and poor substrate specificity, its activity must be well controlled under different conditions. Only a few regulators of RNase E are known, limiting our understanding on posttranscriptional regulatory mechanisms in bacteria. Here we show that, RebA, a protein universally present in cyanobacteria, interacts with RNase E in the cyanobacterium Anabaena PCC 7120. Distinct from those known regulators of RNase E, RebA interacts with the catalytic region of RNase E, and suppresses the cleavage activities of RNase E for all tested substrates. Consistent with the inhibitory function of RebA on RNase E, depletion of RNase E and overproduction of RebA caused formation of elongated cells, whereas the absence of RebA and overproduction of RNase E resulted in a shorter-cell phenotype. We further showed that the morphological changes caused by altered levels of RNase E or RebA are dependent on their physical interaction. The action of RebA represents a new mechanism, potentially conserved in cyanobacteria, for RNase E regulation. Our findings provide insights into the regulation and the function of RNase E, and demonstrate the importance of balanced RNA metabolism in bacteria.
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Affiliation(s)
- Su-Juan Liu
- Key Laboratory of Algal Biology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430070, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Gui-Ming Lin
- Key Laboratory of Algal Biology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430070, China
| | - Yu-Qi Yuan
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan 430070, China
| | - Wenli Chen
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan 430070, China
| | - Ju-Yuan Zhang
- Key Laboratory of Algal Biology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430070, China
| | - Cheng-Cai Zhang
- Key Laboratory of Algal Biology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430070, China
- Key Laboratory of Lake and Watershed Science for Water Security, Chinese Academy of Sciences, Nanjing 210008, China
- Hubei Hongshan Laboratory, Wuhan 430070, China
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5
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Macorano L, Binny TM, Spiegl T, Klimenko V, Singer A, Oberleitner L, Applegate V, Seyffert S, Stefanski A, Gremer L, Gertzen CGW, Höppner A, Smits SHJ, Nowack ECM. DNA-binding and protein structure of nuclear factors likely acting in genetic information processing in the Paulinella chromatophore. Proc Natl Acad Sci U S A 2023; 120:e2221595120. [PMID: 37364116 PMCID: PMC10319021 DOI: 10.1073/pnas.2221595120] [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: 12/20/2022] [Accepted: 05/25/2023] [Indexed: 06/28/2023] Open
Abstract
The chromatophores in Paulinella are evolutionary-early-stage photosynthetic organelles. Biological processes in chromatophores depend on a combination of chromatophore and nucleus-encoded proteins. Interestingly, besides proteins carrying chromatophore-targeting signals, a large arsenal of short chromatophore-targeted proteins (sCTPs; <90 amino acids) without recognizable targeting signals were found in chromatophores. This situation resembles endosymbionts in plants and insects that are manipulated by host-derived antimicrobial peptides. Previously, we identified an expanded family of sCTPs of unknown function, named here "DNA-binding (DB)-sCTPs". DB-sCTPs contain a ~45 amino acid motif that is conserved in some bacterial proteins with predicted functions in DNA processing. Here, we explored antimicrobial activity, DNA-binding capacity, and structures of three purified recombinant DB-sCTPs. All three proteins exhibited antimicrobial activity against bacteria involving membrane permeabilization, and bound to bacterial lipids in vitro. A combination of in vitro assays demonstrated binding of recombinant DB-sCTPs to chromatophore-derived genomic DNA sequences with an affinity in the low nM range. Additionally, we report the 1.2 Å crystal structure of one DB-sCTP. In silico docking studies suggest that helix α2 inserts into the DNA major grove and the exposed residues, that are highly variable between different DB-sCTPs, confer interaction with the DNA bases. Identification of photosystem II subunit CP43 as a potential interaction partner of one DB-sCTP, suggests DB-sCTPs to be involved in more complex regulatory mechanisms. We hypothesize that membrane binding of DB-sCTPs is related to their import into chromatophores. Once inside, they interact with the chromatophore genome potentially providing nuclear control over genetic information processing.
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Affiliation(s)
- Luis Macorano
- Institute of Microbial Cell Biology, Department of Biology, Heinrich Heine University Düsseldorf, 40225Düsseldorf, Germany
| | - Taniya M. Binny
- Institute of Microbial Cell Biology, Department of Biology, Heinrich Heine University Düsseldorf, 40225Düsseldorf, Germany
| | - Tobias Spiegl
- Institute of Microbial Cell Biology, Department of Biology, Heinrich Heine University Düsseldorf, 40225Düsseldorf, Germany
| | - Victoria Klimenko
- Institute of Microbial Cell Biology, Department of Biology, Heinrich Heine University Düsseldorf, 40225Düsseldorf, Germany
| | - Anna Singer
- Institute of Microbial Cell Biology, Department of Biology, Heinrich Heine University Düsseldorf, 40225Düsseldorf, Germany
| | - Linda Oberleitner
- Institute of Microbial Cell Biology, Department of Biology, Heinrich Heine University Düsseldorf, 40225Düsseldorf, Germany
| | - Violetta Applegate
- Center for Structural Studies, Heinrich Heine University Düsseldorf, 40225Düsseldorf, Germany
| | - Sarah Seyffert
- Institute of Microbial Cell Biology, Department of Biology, Heinrich Heine University Düsseldorf, 40225Düsseldorf, Germany
| | - Anja Stefanski
- Molecular Proteomics Laboratory, Medical Faculty and University Hospital, Heinrich Heine University Düsseldorf, 40225Düsseldorf, Germany
| | - Lothar Gremer
- Institute of Biological Information Processing (IBI-7 Structural Biochemistry) and JuStruct Jülich Center of Structural Biology, Forschungszentrum Jülich, 52428Jülich, Germany
- Institute of Physical Biology, Department of Biology, Heinrich Heine University Düsseldorf, 40225Düsseldorf, Germany
| | - Christoph G. W. Gertzen
- Center for Structural Studies, Heinrich Heine University Düsseldorf, 40225Düsseldorf, Germany
- Institute for Pharmaceutical and Medicinal Chemistry, Department of Pharmacy, Heinrich Heine University Düsseldorf, 40225Düsseldorf, Germany
| | - Astrid Höppner
- Center for Structural Studies, Heinrich Heine University Düsseldorf, 40225Düsseldorf, Germany
| | - Sander H. J. Smits
- Center for Structural Studies, Heinrich Heine University Düsseldorf, 40225Düsseldorf, Germany
- Institute of Biochemistry, Department of Chemistry, Heinrich Heine University Düsseldorf, 40225Düsseldorf, Germany
| | - Eva C. M. Nowack
- Institute of Microbial Cell Biology, Department of Biology, Heinrich Heine University Düsseldorf, 40225Düsseldorf, Germany
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6
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Flores Tinoco V, Herrera-Estrella L, Lopez-Arredondo D. Back to primary endosymbiosis: from plastids to artificial photosynthetic life-forms. TRENDS IN PLANT SCIENCE 2023; 28:743-745. [PMID: 37085412 DOI: 10.1016/j.tplants.2023.03.026] [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: 02/20/2023] [Revised: 03/29/2023] [Accepted: 03/30/2023] [Indexed: 05/03/2023]
Abstract
Throughout evolution, only two known primary photosynthetic endosymbiosis occurred, which originated the Archaeplastida and the Paulinella spp. Fundamental questions regarding primary endosymbiosis remain unsolved, but may now be addressed with the recent development of chimeric photosynthetic life-form. Cournoyer et al. could establish artificial photosynthetic endosymbiosis between yeast and cyanobacteria.
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Affiliation(s)
- Valeria Flores Tinoco
- Institute of Genomics for Crop Abiotic Stress Tolerance, Department of Plant and Soil Science, Texas Tech University, Lubbock, TX 79409, USA
| | - Luis Herrera-Estrella
- Institute of Genomics for Crop Abiotic Stress Tolerance, Department of Plant and Soil Science, Texas Tech University, Lubbock, TX 79409, USA; Unidad de Genómica Avanzada/LANGEBIO, Centro de Investigación y de Estudios Avanzados, Irapuato, México
| | - Damar Lopez-Arredondo
- Institute of Genomics for Crop Abiotic Stress Tolerance, Department of Plant and Soil Science, Texas Tech University, Lubbock, TX 79409, USA.
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7
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Van Etten J, Benites LF, Stephens TG, Yoon HS, Bhattacharya D. Algae obscura: The potential of rare species as model systems. JOURNAL OF PHYCOLOGY 2023; 59:293-300. [PMID: 36764681 DOI: 10.1111/jpy.13321] [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: 01/26/2023] [Accepted: 01/28/2023] [Indexed: 05/28/2023]
Abstract
Model organism research has provided invaluable knowledge about foundational biological principles. However, most of these studies have focused on species that are in high abundance, easy to cultivate in the lab, and represent only a small fraction of extant biodiversity. Here, we present three examples of rare algae with unusual features that we refer to as "algae obscura." The Cyanidiophyceae (Rhodophyta), Glaucophyta, and Paulinella (rhizarian) lineages have all transitioned out of obscurity to become models for fundamental evolutionary research. Insights have been gained into the prevalence and importance of eukaryotic horizontal gene transfer, early Earth microbial community dynamics, primary plastid endosymbiosis, and the origin of Archaeplastida. By reviewing the research that has come from the exploration of these organisms, we demonstrate that underappreciated algae have the potential to help us formulate, refine, and substantiate core hypotheses and that such organisms should be considered when establishing future model systems.
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Affiliation(s)
- Julia Van Etten
- Graduate Program in Ecology and Evolution, Rutgers, The State University of New Jersey, New Brunswick, New Jersey, USA
| | - Luiz Felipe Benites
- Department of Biochemistry and Microbiology, Rutgers, The State University of New Jersey, New Brunswick, New Jersey, USA
| | - Timothy G Stephens
- Department of Biochemistry and Microbiology, Rutgers, The State University of New Jersey, New Brunswick, New Jersey, USA
| | - Hwan Su Yoon
- Department of Biological Sciences, Sungkyunkwan University, Suwon, South Korea
| | - Debashish Bhattacharya
- Department of Biochemistry and Microbiology, Rutgers, The State University of New Jersey, New Brunswick, New Jersey, USA
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8
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Kalu EI, Reyes-Prieto A, Barbeau MA. Community dynamics of microbial eukaryotes in intertidal mudflats in the hypertidal Bay of Fundy. ISME COMMUNICATIONS 2023; 3:21. [PMID: 36918616 PMCID: PMC10014957 DOI: 10.1038/s43705-023-00226-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2022] [Revised: 02/15/2023] [Accepted: 02/28/2023] [Indexed: 03/16/2023]
Abstract
Protists (microbial eukaryotes) are a critically important but understudied group of microorganisms. They are ubiquitous, represent most of the genetic and functional diversity among eukaryotes, and play essential roles in nutrient and energy cycling. Yet, protists remain a black box in marine sedimentary ecosystems like the intertidal mudflats in the Bay of Fundy. The harsh conditions of the intertidal zone and high energy nature of tides in the Bay of Fundy provide an ideal system for gaining insights into the major food web players, diversity patterns and potential structuring influences of protist communities. Our 18S rDNA metabarcoding study quantified seasonal variations and vertical stratification of protist communities in Bay of Fundy mudflat sediments. Three 'SAR' lineages were consistently dominant (in terms of abundance, richness, and prevalence), drove overall community dynamics and formed the core microbiome in sediments. They are Cercozoa (specifically thecate, benthic gliding forms), Bacillariophyta (mainly cosmopolitan, typically planktonic diatoms), and Dinophyceae (dominated by a toxigenic, bloom-forming species). Consumers were the dominant trophic functional group and were comprised mostly of eukaryvorous and bacterivorous Cercozoa, and omnivorous Ciliophora, while phototrophs were dominated by Bacillariophyta. The codominance of Apicomplexa (invertebrate parasites) and Syndiniales (protist parasites) in parasite assemblages, coupled with broader diversity patterns, highlighted the combined marine and terrestrial influences on microbial communities inhabiting intertidal sediments. Our findings, the most comprehensive in a hypertidal benthic system, suggest that synergistic interactions of both local and regional processes (notably benthic-pelagic coupling) may drive heterogenous microbial distribution in high-energy coastal systems.
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Affiliation(s)
- Eke I Kalu
- Department of Biology, University of New Brunswick, Fredericton, NB, Canada.
| | | | - Myriam A Barbeau
- Department of Biology, University of New Brunswick, Fredericton, NB, Canada
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9
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Mitsi K, Richter DJ, Arroyo AS, López-Escardó D, Antó M, Oterino AG, Ruiz-Trillo I. Taxonomic composition, community structure and molecular novelty of microeukaryotes in a temperate oligomesotrophic lake as revealed by metabarcoding. Sci Rep 2023; 13:3119. [PMID: 36813945 PMCID: PMC9947120 DOI: 10.1038/s41598-023-30228-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2022] [Accepted: 02/18/2023] [Indexed: 02/24/2023] Open
Abstract
Microbial eukaryotes are diverse and ecologically important organisms, yet sampling constraints have hindered the understanding of their distribution and diversity in freshwater ecosystems. Metabarcoding has provided a powerful complement to traditional limnological studies, revealing an unprecedented diversity of protists in freshwater environments. Here, we aim to expand our knowledge of the ecology and diversity of protists in lacustrine ecosystems by targeting the V4 hypervariable region of the 18S rRNA gene in water column, sediment and biofilm samples collected from Sanabria Lake (Spain) and surrounding freshwater ecosystems. Sanabria is a temperate lake, which are relatively understudied by metabarcoding in comparison to alpine and polar lakes. The phylogenetic diversity of microbial eukaryotes detected in Sanabria spans all currently recognized eukaryotic supergroups, with Stramenopiles being the most abundant and diverse supergroup in all sampling sites. Parasitic microeukaryotes account for 21% of the total protist ASVs identified in our study and were dominated by Chytridiomycota, both in terms of richness and abundance, in all sampling sites. Sediments, biofilms and water column samples harbour distinct microbial communities. Phylogenetic placement of poorly assigned and abundant ASVs indicates molecular novelty inside Rhodophyta, Bigyra, early-branching Nucletmycea and Apusomonadida. In addition, we report the first freshwater incidence of the previously exclusively marine genera Abeoforma and Sphaeroforma. Our results contribute to a deeper understanding of microeukaryotic communities in freshwater ecosystems, and provide the first molecular reference for future biomonitoring surveys in Sanabria Lake.
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Affiliation(s)
- Konstantina Mitsi
- Institut de Biologia Evolutiva (CSIC-Universitat Pompeu Fabra), Passeig Marítim de La Barceloneta, 37-49, 08033, Barcelona, Spain.
| | - Daniel J. Richter
- grid.507636.10000 0004 0424 5398Institut de Biologia Evolutiva (CSIC-Universitat Pompeu Fabra), Passeig Marítim de La Barceloneta, 37-49, 08033 Barcelona, Spain
| | - Alicia S. Arroyo
- grid.507636.10000 0004 0424 5398Institut de Biologia Evolutiva (CSIC-Universitat Pompeu Fabra), Passeig Marítim de La Barceloneta, 37-49, 08033 Barcelona, Spain
| | - David López-Escardó
- grid.418218.60000 0004 1793 765XInstitut de Ciències del Mar (CSIC), Passeig Marítim de La Barceloneta, 37-49, 08033 Barcelona, Spain
| | - Meritxell Antó
- grid.507636.10000 0004 0424 5398Institut de Biologia Evolutiva (CSIC-Universitat Pompeu Fabra), Passeig Marítim de La Barceloneta, 37-49, 08033 Barcelona, Spain
| | | | - Iñaki Ruiz-Trillo
- grid.507636.10000 0004 0424 5398Institut de Biologia Evolutiva (CSIC-Universitat Pompeu Fabra), Passeig Marítim de La Barceloneta, 37-49, 08033 Barcelona, Spain ,grid.425902.80000 0000 9601 989XInstitució Catalana de Recerca I Estudis Avançats (ICREA), Passeig Lluís Companys, 23, 08010 Barcelona, Spain
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10
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Phycobilisomes and Phycobiliproteins in the Pigment Apparatus of Oxygenic Photosynthetics: From Cyanobacteria to Tertiary Endosymbiosis. Int J Mol Sci 2023; 24:ijms24032290. [PMID: 36768613 PMCID: PMC9916406 DOI: 10.3390/ijms24032290] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2022] [Revised: 01/15/2023] [Accepted: 01/19/2023] [Indexed: 01/26/2023] Open
Abstract
Eukaryotic photosynthesis originated in the course of evolution as a result of the uptake of some unstored cyanobacterium and its transformation to chloroplasts by an ancestral heterotrophic eukaryotic cell. The pigment apparatus of Archaeplastida and other algal phyla that emerged later turned out to be arranged in the same way. Pigment-protein complexes of photosystem I (PS I) and photosystem II (PS II) are characterized by uniform structures, while the light-harvesting antennae have undergone a series of changes. The phycobilisome (PBS) antenna present in cyanobacteria was replaced by Chl a/b- or Chl a/c-containing pigment-protein complexes in most groups of photosynthetics. In the form of PBS or phycobiliprotein aggregates, it was inherited by members of Cyanophyta, Cryptophyta, red algae, and photosynthetic amoebae. Supramolecular organization and architectural modifications of phycobiliprotein antennae in various algal phyla in line with the endosymbiotic theory of chloroplast origin are the subject of this review.
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11
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Kroth PG. On the origin of plastids. Bioessays 2023; 45:e2200217. [PMID: 36385390 DOI: 10.1002/bies.202200217] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2022] [Accepted: 11/07/2022] [Indexed: 11/19/2022]
Affiliation(s)
- Peter G Kroth
- Department of Biology, Universität Konstanz, Konstanz, Germany
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12
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Evolutionary inference across eukaryotes identifies universal features shaping organelle gene retention. Cell Syst 2022; 13:874-884.e5. [PMID: 36115336 DOI: 10.1016/j.cels.2022.08.007] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Revised: 06/24/2022] [Accepted: 08/22/2022] [Indexed: 01/26/2023]
Abstract
Mitochondria and plastids power complex life. Why some genes and not others are retained in their organelle DNA (oDNA) genomes remains a debated question. Here, we attempt to identify the properties of genes and associated underlying mechanisms that determine oDNA retention. We harness over 15k oDNA sequences and over 300 whole genome sequences across eukaryotes with tools from structural biology, bioinformatics, machine learning, and Bayesian model selection. Previously hypothesized features, including the hydrophobicity of a protein product, and less well-known features, including binding energy centrality within a protein complex, predict oDNA retention across eukaryotes, with additional influences of nucleic acid and amino acid biochemistry. Notably, the same features predict retention in both organelles, and retention models learned from one organelle type quantitatively predict retention in the other, supporting the universality of these features-which also distinguish gene profiles in more recent, independent endosymbiotic relationships. A record of this paper's transparent peer review process is included in the supplemental information.
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Loss of key endosymbiont genes may facilitate early host control of the chromatophore in Paulinella. iScience 2022; 25:104974. [PMID: 36093053 PMCID: PMC9450145 DOI: 10.1016/j.isci.2022.104974] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Revised: 07/14/2022] [Accepted: 08/15/2022] [Indexed: 01/12/2023] Open
Abstract
The primary plastid endosymbiosis (∼124 Mya) that occurred in the heterotrophic amoeba lineage, Paulinella, is at an earlier stage of evolution than in Archaeplastida, and provides an excellent model for studying organelle integration. Using genomic data from photosynthetic Paulinella, we identified a plausible mechanism for the evolution of host control of endosymbiont (termed the chromatophore) biosynthetic pathways and functions. Specifically, random gene loss from the chromatophore and compensation by nuclear-encoded gene copies enables host control of key pathways through a minimal number of evolutionary innovations. These gene losses impact critical enzymatic steps in nucleotide biosynthesis and the more peripheral components of multi-protein DNA replication complexes. Gene retention in the chromatophore likely reflects the need to maintain a specific stoichiometric balance of the encoded products (e.g., involved in DNA replication) rather than redox state, as in the highly reduced plastid genomes of algae and plants. Endosymbiont DNA replication cannot be completed without several key host proteins Endosymbiont nucleotide biosynthesis is completed by import of host proteins Limited gene loss allowed the host to gain control of endosymbiont division Paulinella regulates chromatophore function using the stringent response pathway
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14
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Gabr A, Stephens TG, Bhattacharya D. Hypothesis: Trans-splicing Generates Evolutionary Novelty in the Photosynthetic Amoeba Paulinella. JOURNAL OF PHYCOLOGY 2022; 58:392-405. [PMID: 35255163 PMCID: PMC9311404 DOI: 10.1111/jpy.13247] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2021] [Revised: 02/10/2022] [Accepted: 02/14/2022] [Indexed: 05/19/2023]
Abstract
Plastid primary endosymbiosis has occurred twice, once in the Archaeplastida ancestor and once in the Paulinella (Rhizaria) lineage. Both events precipitated massive evolutionary changes, including the recruitment and activation of genes that are horizontally acquired (HGT) and the redeployment of existing genes and pathways in novel contexts. Here we address the latter aspect in Paulinella micropora KR01 (hereafter, KR01) that has independently evolved spliced leader (SL) trans-splicing (SLTS) of nuclear-derived transcripts. We investigated the role of this process in gene regulation, novel gene origination, and endosymbiont integration. Our analysis shows that 20% of KR01 genes give rise to transcripts with at least one (but in some cases, multiple) sites of SL addition. This process, which often occurs at canonical cis-splicing acceptor sites (internal introns), results in shorter transcripts that may produce 5'-truncated proteins with novel functions. SL-truncated transcripts fall into four categories that may show: (i) altered protein localization, (ii) altered protein function, structure, or regulation, (iii) loss of valid alternative start codons, preventing translation, or (iv) multiple SL addition sites at the 5'-terminus. The SL RNA genes required for SLTS are putatively absent in the heterotrophic sister lineage of photosynthetic Paulinella species. Moreover, a high proportion of transcripts derived from genes of endosymbiotic gene transfer (EGT) and HGT origin contain SL sequences. We hypothesize that truncation of transcripts by SL addition may facilitate the generation and expression of novel gene variants and that SLTS may have enhanced the activation and fixation of foreign genes in the host genome of the photosynthetic lineages, playing a key role in primary endosymbiont integration.
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Affiliation(s)
- Arwa Gabr
- Graduate Program in Molecular Bioscience and Program in Microbiology and Molecular GeneticsRutgers UniversityNew BrunswickNew Jersey08901USA
| | - Timothy G. Stephens
- Department of Biochemistry and MicrobiologyRutgers UniversityNew BrunswickNew Jersey08901USA
| | - Debashish Bhattacharya
- Department of Biochemistry and MicrobiologyRutgers UniversityNew BrunswickNew Jersey08901USA
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15
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Oberleitner L, Perrar A, Macorano L, Huesgen PF, Nowack ECM. A bipartite chromatophore transit peptide and N-terminal protein processing in the Paulinella chromatophore. PLANT PHYSIOLOGY 2022; 189:152-164. [PMID: 35043947 PMCID: PMC9070848 DOI: 10.1093/plphys/kiac012] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2021] [Accepted: 12/06/2021] [Indexed: 05/19/2023]
Abstract
The amoeba Paulinella chromatophora contains photosynthetic organelles, termed chromatophores, which evolved independently from plastids in plants and algae. At least one-third of the chromatophore proteome consists of nucleus-encoded (NE) proteins that are imported across the chromatophore double envelope membranes. Chromatophore-targeted proteins exceeding 250 amino acids (aa) carry a conserved N-terminal extension presumably involved in protein targeting, termed the chromatophore transit peptide (crTP). Short imported proteins do not carry discernable targeting signals. To explore whether the import of proteins is accompanied by their N-terminal processing, here we identified N-termini of 208 chromatophore-localized proteins by a mass spectrometry-based approach. Our study revealed extensive N-terminal acetylation and proteolytic processing in both NE and chromatophore-encoded (CE) fractions of the chromatophore proteome. Mature N-termini of 37 crTP-carrying proteins were identified, of which 30 were cleaved in a common processing region. Surprisingly, only the N-terminal ∼50 aa (part 1) become cleaved upon import. This part contains a conserved adaptor protein-1 complex-binding motif known to mediate protein sorting at the trans-Golgi network followed by a predicted transmembrane helix, implying that part 1 anchors the protein co-translationally in the endoplasmic reticulum and mediates trafficking to the chromatophore via the Golgi. The C-terminal part 2 contains conserved secondary structural elements, remains attached to the mature proteins, and might mediate translocation across the chromatophore inner membrane. Short imported proteins remain largely unprocessed. Finally, this work illuminates N-terminal processing of proteins encoded in an evolutionary-early-stage organelle and suggests host-derived posttranslationally acting factors involved in regulation of the CE chromatophore proteome.
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Affiliation(s)
- Linda Oberleitner
- Department of Biology, Institute of Microbial Cell Biology, Heinrich Heine University Düsseldorf, 40225 Düsseldorf, Germany
| | - Andreas Perrar
- Central Institute for Engineering, Electronics and Analytics, ZEA-3, Forschungszentrum Jülich, 52425 Jülich, Germany
- Cologne Excellence Cluster on Stress Responses in Ageing-Associated Diseases, CECAD, Medical Faculty and University Hospital, University of Cologne, 50931 Cologne, Germany
| | - Luis Macorano
- Department of Biology, Institute of Microbial Cell Biology, Heinrich Heine University Düsseldorf, 40225 Düsseldorf, Germany
| | - Pitter F Huesgen
- Central Institute for Engineering, Electronics and Analytics, ZEA-3, Forschungszentrum Jülich, 52425 Jülich, Germany
- Cologne Excellence Cluster on Stress Responses in Ageing-Associated Diseases, CECAD, Medical Faculty and University Hospital, University of Cologne, 50931 Cologne, Germany
- Department of Chemistry, Institute of Biochemistry, University of Cologne, 50674 Cologne, Germany
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16
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Gabr A, Zournas A, Stephens TG, Dismukes GC, Bhattacharya D. Evidence for a robust photosystem II in the photosynthetic amoeba Paulinella. THE NEW PHYTOLOGIST 2022; 234:934-945. [PMID: 35211975 DOI: 10.1111/nph.18052] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2021] [Accepted: 02/06/2022] [Indexed: 06/14/2023]
Abstract
Paulinella represents the only known case of an independent primary plastid endosymbiosis, outside Archaeplastida, that occurred c. 120 (million years ago) Ma. These photoautotrophs grow very slowly in replete culture medium with a doubling time of 6-7 d at optimal low light, and are highly sensitive to photodamage under moderate light levels. We used genomic and biophysical methods to investigate the extreme slow growth rate and light sensitivity of Paulinella, which are key to photosymbiont integration. All photosystem II (PSII) genes except psb28-2 and all cytochrome b6 f complex genes except petM and petL are present in Paulinella micropora KR01 (hereafter, KR01). Biophysical measurements of the water oxidation complex, variable chlorophyll fluorescence, and photosynthesis-irradiance curves show no obvious evidence of PSII impairment. Analysis of photoacclimation under high-light suggests that although KR01 can perform charge separation, it lacks photoprotection mechanisms present in cyanobacteria. We hypothesize that Paulinella species are restricted to low light environments because they are deficient in mitigating the formation of reactive oxygen species formed within the photosystems under peak solar intensities. The finding that many photoprotection genes have been lost or transferred to the host-genome during endosymbiont genome reduction, and may lack light-regulation, is consistent with this hypothesis.
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Affiliation(s)
- Arwa Gabr
- Graduate Program in Molecular Bioscience and Program in Microbiology and Molecular Genetics, Rutgers University, Nelson Lab-604 Allison Road, Piscataway, NJ, 08854, USA
| | - Apostolos Zournas
- Graduate Program in Chemical and Biochemical Engineering, Rutgers University, 98 Brett Road, Piscataway, NJ, 08854, USA
- The Waksman Institute, Rutgers University, 190 Frelinghuysen Road, Piscataway, NJ, 08854, USA
| | - Timothy G Stephens
- Department of Biochemistry and Microbiology, Rutgers University, Lipman Drive, New Brunswick, NJ, 08901, USA
| | - G Charles Dismukes
- The Waksman Institute, Rutgers University, 190 Frelinghuysen Road, Piscataway, NJ, 08854, USA
- Department of Chemistry and Chemical Biology, Rutgers University, 123 Bevier Road, Piscataway, NJ, 08854, USA
| | - Debashish Bhattacharya
- Department of Biochemistry and Microbiology, Rutgers University, Lipman Drive, New Brunswick, NJ, 08901, USA
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Sanders WB. The photoaerogens: algae and plants reunited conceptually. AMERICAN JOURNAL OF BOTANY 2022; 109:363-365. [PMID: 35257370 DOI: 10.1002/ajb2.1828] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2021] [Revised: 12/16/2021] [Accepted: 12/22/2021] [Indexed: 06/14/2023]
Affiliation(s)
- William B Sanders
- Department of Biological Sciences, Florida Gulf Coast University, Ft. Myers, FL 33965-6565, USA
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18
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Uthanumallian K, Iha C, Repetti SI, Chan CX, Bhattacharya D, Duchene S, Verbruggen H. Tightly Constrained Genome Reduction and Relaxation of Purifying Selection during Secondary Plastid Endosymbiosis. Mol Biol Evol 2022; 39:msab295. [PMID: 34613411 PMCID: PMC8763093 DOI: 10.1093/molbev/msab295] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Endosymbiosis, the establishment of a former free-living prokaryotic or eukaryotic cell as an organelle inside a host cell, can dramatically alter the genomic architecture of the endosymbiont. Plastids or chloroplasts, the light-harvesting organelle of photosynthetic eukaryotes, are excellent models to study this phenomenon because plastid origin has occurred multiple times in evolution. Here, we investigate the genomic signature of molecular processes acting through secondary plastid endosymbiosis-the origination of a new plastid from a free-living eukaryotic alga. We used phylogenetic comparative methods to study gene loss and changes in selective regimes on plastid genomes, focusing on green algae that have given rise to three independent lineages with secondary plastids (euglenophytes, chlorarachniophytes, and Lepidodinium). Our results show an overall increase in gene loss associated with secondary endosymbiosis, but this loss is tightly constrained by the retention of genes essential for plastid function. The data show that secondary plastids have experienced temporary relaxation of purifying selection during secondary endosymbiosis. However, this process is tightly constrained, with selection relaxed only relative to the background in primary plastids. Purifying selection remains strong in absolute terms even during the endosymbiosis events. Selection intensity rebounds to pre-endosymbiosis levels following endosymbiosis events, demonstrating the changes in selection efficiency during different origin phases of secondary plastids. Independent endosymbiosis events in the euglenophytes, chlorarachniophytes, and Lepidodinium differ in their degree of relaxation of selection, highlighting the different evolutionary contexts of these events. This study reveals the selection-drift interplay during secondary endosymbiosis and evolutionary parallels during organellogenesis.
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Affiliation(s)
| | - Cintia Iha
- School of BioSciences, University of Melbourne, Melbourne, VIC, Australia
| | - Sonja I Repetti
- School of BioSciences, University of Melbourne, Melbourne, VIC, Australia
| | - Cheong Xin Chan
- Australian Centre for Ecogenomics, School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, QLD, Australia
| | | | - Sebastian Duchene
- Deptartment of Microbiology and Immunology, Peter Doherty Institute for Infection and Immunity, University of Melbourne, Melbourne, VIC, Australia
| | - Heroen Verbruggen
- School of BioSciences, University of Melbourne, Melbourne, VIC, Australia
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Stephens TG, Gabr A, Calatrava V, Grossman AR, Bhattacharya D. Why is primary endosymbiosis so rare? THE NEW PHYTOLOGIST 2021; 231:1693-1699. [PMID: 34018613 PMCID: PMC8711089 DOI: 10.1111/nph.17478] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Accepted: 05/05/2021] [Indexed: 05/05/2023]
Abstract
Endosymbiosis is a relationship between two organisms wherein one cell resides inside the other. This affiliation, when stable and beneficial for the 'host' cell, can result in massive genetic innovation with the foremost examples being the evolution of eukaryotic organelles, the mitochondria and plastids. Despite its critical evolutionary role, there is limited knowledge about how endosymbiosis is initially established and how host-endosymbiont biology is integrated. Here, we explore this issue, using as our model the rhizarian amoeba Paulinella, which represents an independent case of primary plastid origin that occurred c. 120 million yr ago. We propose the 'chassis and engine' model that provides a theoretical framework for understanding primary plastid endosymbiosis, potentially explaining why it is so rare.
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Affiliation(s)
- Timothy G. Stephens
- Department of Biochemistry and Microbiology, Rutgers University, New Brunswick, NJ 08901, USA
| | - Arwa Gabr
- Graduate Program in Molecular Bioscience and Program in Microbiology and Molecular Genetics, Rutgers University, Piscataway, NJ 08854, USA
| | - Victoria Calatrava
- Department of Plant Biology, The Carnegie Institution, Stanford, CA 94305, USA
| | - Arthur R. Grossman
- Department of Plant Biology, The Carnegie Institution, Stanford, CA 94305, USA
| | - Debashish Bhattacharya
- Department of Biochemistry and Microbiology, Rutgers University, New Brunswick, NJ 08901, USA
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20
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Horizontal Gene Transfer in Eukaryotes: Not if, but How Much? Trends Genet 2020; 36:915-925. [DOI: 10.1016/j.tig.2020.08.006] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2020] [Revised: 07/31/2020] [Accepted: 08/10/2020] [Indexed: 12/17/2022]
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21
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Oberleitner L, Poschmann G, Macorano L, Schott-Verdugo S, Gohlke H, Stühler K, Nowack ECM. The Puzzle of Metabolite Exchange and Identification of Putative Octotrico Peptide Repeat Expression Regulators in the Nascent Photosynthetic Organelles of Paulinella chromatophora. Front Microbiol 2020; 11:607182. [PMID: 33329499 PMCID: PMC7729196 DOI: 10.3389/fmicb.2020.607182] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2020] [Accepted: 11/05/2020] [Indexed: 12/12/2022] Open
Abstract
The endosymbiotic acquisition of mitochondria and plastids more than one billion years ago was central for the evolution of eukaryotic life. However, owing to their ancient origin, these organelles provide only limited insights into the initial stages of organellogenesis. The cercozoan amoeba Paulinella chromatophora contains photosynthetic organelles-termed chromatophores-that evolved from a cyanobacterium ∼100 million years ago, independently from plastids in plants and algae. Despite the more recent origin of the chromatophore, it shows tight integration into the host cell. It imports hundreds of nucleus-encoded proteins, and diverse metabolites are continuously exchanged across the two chromatophore envelope membranes. However, the limited set of chromatophore-encoded solute transporters appears insufficient for supporting metabolic connectivity or protein import. Furthermore, chromatophore-localized biosynthetic pathways as well as multiprotein complexes include proteins of dual genetic origin, suggesting that mechanisms evolved that coordinate gene expression levels between chromatophore and nucleus. These findings imply that similar to the situation in mitochondria and plastids, also in P. chromatophora nuclear factors evolved that control metabolite exchange and gene expression in the chromatophore. Here we show by mass spectrometric analyses of enriched insoluble protein fractions that, unexpectedly, nucleus-encoded transporters are not inserted into the chromatophore inner envelope membrane. Thus, despite the apparent maintenance of its barrier function, canonical metabolite transporters are missing in this membrane. Instead we identified several expanded groups of short chromatophore-targeted orphan proteins. Members of one of these groups are characterized by a single transmembrane helix, and others contain amphipathic helices. We hypothesize that these proteins are involved in modulating membrane permeability. Thus, the mechanism generating metabolic connectivity of the chromatophore fundamentally differs from the one for mitochondria and plastids, but likely rather resembles the poorly understood mechanism in various bacterial endosymbionts in plants and insects. Furthermore, our mass spectrometric analysis revealed an expanded family of chromatophore-targeted helical repeat proteins. These proteins show similar domain architectures as known organelle-targeted expression regulators of the octotrico peptide repeat type in algae and plants. Apparently these chromatophore-targeted proteins evolved convergently to plastid-targeted expression regulators and are likely involved in gene expression control in the chromatophore.
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Affiliation(s)
- Linda Oberleitner
- Department of Biology, Institute of Microbial Cell Biology, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
| | - Gereon Poschmann
- Medical Faculty, Institute for Molecular Medicine, Proteome Research, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
| | - Luis Macorano
- Department of Biology, Institute of Microbial Cell Biology, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
| | - Stephan Schott-Verdugo
- Department of Pharmacy, Institute for Pharmaceutical and Medicinal Chemistry, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
- Faculty of Engineering, Centro de Bioinformática y Simulación Molecular, Universidad de Talca, Talca, Chile
| | - Holger Gohlke
- Department of Pharmacy, Institute for Pharmaceutical and Medicinal Chemistry, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
- Jülich Supercomputing Centre, John von Neumann Institute for Computing, Institute of Biological Information Processing (IBI-7: Structural Biochemistry), Forschungszentrum Jülich GmbH, Jülich, Germany
| | - Kai Stühler
- Medical Faculty, Institute for Molecular Medicine, Proteome Research, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
- Molecular Proteomics Laboratory, Biologisch-Medizinisches Forschungszentrum, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
| | - Eva C. M. Nowack
- Department of Biology, Institute of Microbial Cell Biology, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
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