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Chen Z, Wang X, Li S, Yao J, Shao Z, Duan D. Verification of the Saccharina japonica Translocon Tic20 and its Localization in the Chloroplast Membrane in Diatoms. Int J Mol Sci 2019; 20:E4000. [PMID: 31426420 PMCID: PMC6720183 DOI: 10.3390/ijms20164000] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2019] [Revised: 08/01/2019] [Accepted: 08/15/2019] [Indexed: 12/21/2022] Open
Abstract
Tic20 is an important translocon protein that plays a role in protein transport in the chloroplast. The sequence of Tic20 was determined in the lower brown alga Saccharina japonica. Structural analysis of SjTic20 revealed a noncanonical structure consisting of an N-terminal non-cyanobacterium-originated EF-hand domain (a helix-loop-helix structural domain) and a C-terminal cyanobacterium-originated Tic20 domain. Subcellular localization and transmembrane analysis indicated that SjTic20 featured an "M"-type Nin-Cin-terminal orientation, with four transmembrane domains in the innermost membrane of the chloroplast in the microalga Phaeodactylum tricornutum, and the EF-hand domain was entirely extruded into the chloroplast stroma. Our study provides information on the structure, localization, and topological features of SjTic20, and further functional analysis of SjTic20 in S. japonica is needed.
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Affiliation(s)
- Zhihang Chen
- Key Laboratory of Experimental Marine Biology, Center for Ocean Mega-Science, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China
- Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266071, China
- University of Chinese Academy of Sciences, Beijing 100093, China
| | - Xiuliang Wang
- Key Laboratory of Experimental Marine Biology, Center for Ocean Mega-Science, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China.
- Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266071, China.
| | - Shuang Li
- Key Laboratory of Experimental Marine Biology, Center for Ocean Mega-Science, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China
- Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266071, China
- University of Chinese Academy of Sciences, Beijing 100093, China
| | - Jianting Yao
- Key Laboratory of Experimental Marine Biology, Center for Ocean Mega-Science, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China
- Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266071, China
| | - Zhanru Shao
- Key Laboratory of Experimental Marine Biology, Center for Ocean Mega-Science, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China
- Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266071, China
| | - Delin Duan
- Key Laboratory of Experimental Marine Biology, Center for Ocean Mega-Science, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China.
- Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266071, China.
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2
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Guo L, Liang S, Zhang Z, Liu H, Wang S, Pan K, Xu J, Ren X, Pei S, Yang G. Genome assembly of Nannochloropsis oceanica provides evidence of host nucleus overthrow by the symbiont nucleus during speciation. Commun Biol 2019; 2:249. [PMID: 31286066 PMCID: PMC6610115 DOI: 10.1038/s42003-019-0500-9] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2018] [Accepted: 05/29/2019] [Indexed: 11/08/2022] Open
Abstract
The species of the genus Nannochloropsis are unique in their maintenance of a nucleus-plastid continuum throughout their cell cycle, non-motility and asexual reproduction. These characteristics should have been endorsed in their gene assemblages (genomes). Here we show that N. oceanica has a genome of 29.3 Mb consisting of 32 pseudochromosomes and containing 7,330 protein-coding genes; and the host nucleus may have been overthrown by an ancient red alga symbiont nucleus during speciation through secondary endosymbiosis. In addition, N. oceanica has lost its flagella and abilities to undergo meiosis and sexual reproduction, and adopted a genome reduction strategy during speciation. We propose that N. oceanica emerged through the active fusion of a host protist and a photosynthesizing ancient red alga and the symbiont nucleus became dominant over the host nucleus while the chloroplast was wrapped by two layers of endoplasmic reticulum. Our findings evidenced an alternative speciation pathway of eukaryotes.
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Affiliation(s)
- Li Guo
- College of Marine Life Sciences, Ocean University of China (OUC), Qingdao, 266003 P. R. China
| | - Sijie Liang
- College of Marine Life Sciences, Ocean University of China (OUC), Qingdao, 266003 P. R. China
| | - Zhongyi Zhang
- College of Marine Life Sciences, Ocean University of China (OUC), Qingdao, 266003 P. R. China
| | - Hang Liu
- College of Marine Life Sciences, Ocean University of China (OUC), Qingdao, 266003 P. R. China
| | - Songwen Wang
- College of Agriculture and Resources and Environment, Tianjin Agricultural University, Tianjin, 300384 P. R. China
| | - Kehou Pan
- Laboratory of Applied Microalgae, College of Fisheries, OUC, Qingdao, 266003 P. R. China
| | - Jian Xu
- Functional Genomics Group, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, 266101 P. R. China
| | - Xue Ren
- Annoroad Gene Technology (Beijing) Co., Ltd, Beijing, 100176 P. R. China
| | - Surui Pei
- Annoroad Gene Technology (Beijing) Co., Ltd, Beijing, 100176 P. R. China
| | - Guanpin Yang
- College of Marine Life Sciences, Ocean University of China (OUC), Qingdao, 266003 P. R. China
- Institutes of Evolution and Marine Biodiversity, OUC, Qingdao, 266003 P. R. China
- Key Laboratory of Marine Genetics and Breeding of Ministry of Education, OUC, Qingdao, 266003 P. R. China
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3
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Åsman AKM, Curtis BA, Archibald JM. Nucleomorph Small RNAs in Cryptophyte and Chlorarachniophyte Algae. Genome Biol Evol 2019; 11:1117-1134. [PMID: 30949682 PMCID: PMC6461891 DOI: 10.1093/gbe/evz064] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/15/2019] [Indexed: 12/27/2022] Open
Abstract
The regulation of gene expression and RNA maturation underlies fundamental processes such as cell homeostasis, development, and stress acclimation. The biogenesis and modification of RNA is tightly controlled by an array of regulatory RNAs and nucleic acid-binding proteins. While the role of small RNAs (sRNAs) in gene expression has been studied in-depth in select model organisms, little is known about sRNA biology across the eukaryotic tree of life. We used deep sequencing to explore the repertoires of sRNAs encoded by the miniaturized, endosymbiotically derived “nucleomorph” genomes of two single-celled algae, the cryptophyte Guillardia theta and the chlorarachniophyte Bigelowiella natans. A total of 32.3 and 35.3 million reads were generated from G. theta and B. natans, respectively. In G. theta, we identified nucleomorph U1, U2, and U4 spliceosomal small nuclear RNAs (snRNAs) as well as 11 C/D box small nucleolar RNAs (snoRNAs), five of which have potential plant and animal homologs. The snoRNAs are predicted to perform 2′-O methylation of rRNA (but not snRNA). In B. natans, we found the previously undetected 5S rRNA as well as six orphan sRNAs. Analysis of chlorarachniophyte snRNAs shed light on the removal of the miniature 18–21 nt introns found in B. natans nucleomorph genes. Neither of the nucleomorph genomes appears to encode RNA pseudouridylation machinery, and U5 snRNA cannot be found in the cryptophyte G. theta. Considering the central roles of U5 snRNA and RNA modifications in other organisms, cytoplasm-to-nucleomorph RNA shuttling in cryptophyte algae is a distinct possibility.
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Affiliation(s)
- Anna K M Åsman
- Department of Biochemistry and Molecular Biology, Dalhousie University, Nova Scotia, Canada.,Department of Molecular Sciences, Uppsala BioCenter, Swedish University of Agricultural Sciences and Linnean Center for Plant Biology, Uppsala, Sweden
| | - Bruce A Curtis
- Department of Biochemistry and Molecular Biology, Dalhousie University, Nova Scotia, Canada
| | - John M Archibald
- Department of Biochemistry and Molecular Biology, Dalhousie University, Nova Scotia, Canada
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4
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Mallo N, Fellows J, Johnson C, Sheiner L. Protein Import into the Endosymbiotic Organelles of Apicomplexan Parasites. Genes (Basel) 2018; 9:E412. [PMID: 30110980 PMCID: PMC6115763 DOI: 10.3390/genes9080412] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2018] [Revised: 07/31/2018] [Accepted: 08/07/2018] [Indexed: 01/26/2023] Open
Abstract
: The organelles of endosymbiotic origin, plastids, and mitochondria, evolved through the serial acquisition of endosymbionts by a host cell. These events were accompanied by gene transfer from the symbionts to the host, resulting in most of the organellar proteins being encoded in the cell nuclear genome and trafficked into the organelle via a series of translocation complexes. Much of what is known about organelle protein translocation mechanisms is based on studies performed in common model organisms; e.g., yeast and humans or Arabidopsis. However, studies performed in divergent organisms are gradually accumulating. These studies provide insights into universally conserved traits, while discovering traits that are specific to organisms or clades. Apicomplexan parasites feature two organelles of endosymbiotic origin: a secondary plastid named the apicoplast and a mitochondrion. In the context of the diseases caused by apicomplexan parasites, the essential roles and divergent features of both organelles make them prime targets for drug discovery. This potential and the amenability of the apicomplexan Toxoplasma gondii to genetic manipulation motivated research about the mechanisms controlling both organelles' biogenesis. Here we provide an overview of what is known about apicomplexan organelle protein import. We focus on work done mainly in T. gondii and provide a comparison to model organisms.
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Affiliation(s)
- Natalia Mallo
- Wellcome Centre for Molecular Parasitology, University of Glasgow, 120 University Place Glasgow, Glasgow G12 8QQ, UK.
| | - Justin Fellows
- Genetics and Biochemistry Branch, National Institute for Diabetes and Digestive and Kidney Disease, National Institutes of Health, Bethesda, MD 20892, USA.
| | - Carla Johnson
- Wellcome Centre for Molecular Parasitology, University of Glasgow, 120 University Place Glasgow, Glasgow G12 8QQ, UK.
| | - Lilach Sheiner
- Wellcome Centre for Molecular Parasitology, University of Glasgow, 120 University Place Glasgow, Glasgow G12 8QQ, UK.
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Cavalier-Smith T. Kingdom Chromista and its eight phyla: a new synthesis emphasising periplastid protein targeting, cytoskeletal and periplastid evolution, and ancient divergences. PROTOPLASMA 2018; 255:297-357. [PMID: 28875267 PMCID: PMC5756292 DOI: 10.1007/s00709-017-1147-3] [Citation(s) in RCA: 74] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2017] [Accepted: 07/18/2017] [Indexed: 05/18/2023]
Abstract
In 1981 I established kingdom Chromista, distinguished from Plantae because of its more complex chloroplast-associated membrane topology and rigid tubular multipartite ciliary hairs. Plantae originated by converting a cyanobacterium to chloroplasts with Toc/Tic translocons; most evolved cell walls early, thereby losing phagotrophy. Chromists originated by enslaving a phagocytosed red alga, surrounding plastids by two extra membranes, placing them within the endomembrane system, necessitating novel protein import machineries. Early chromists retained phagotrophy, remaining naked and repeatedly reverted to heterotrophy by losing chloroplasts. Therefore, Chromista include secondary phagoheterotrophs (notably ciliates, many dinoflagellates, Opalozoa, Rhizaria, heliozoans) or walled osmotrophs (Pseudofungi, Labyrinthulea), formerly considered protozoa or fungi respectively, plus endoparasites (e.g. Sporozoa) and all chromophyte algae (other dinoflagellates, chromeroids, ochrophytes, haptophytes, cryptophytes). I discuss their origin, evolutionary diversification, and reasons for making chromists one kingdom despite highly divergent cytoskeletons and trophic modes, including improved explanations for periplastid/chloroplast protein targeting, derlin evolution, and ciliary/cytoskeletal diversification. I conjecture that transit-peptide-receptor-mediated 'endocytosis' from periplastid membranes generates periplastid vesicles that fuse with the arguably derlin-translocon-containing periplastid reticulum (putative red algal trans-Golgi network homologue; present in all chromophytes except dinoflagellates). I explain chromist origin from ancestral corticates and neokaryotes, reappraising tertiary symbiogenesis; a chromist cytoskeletal synapomorphy, a bypassing microtubule band dextral to both centrioles, favoured multiple axopodial origins. I revise chromist higher classification by transferring rhizarian subphylum Endomyxa from Cercozoa to Retaria; establishing retarian subphylum Ectoreta for Foraminifera plus Radiozoa, apicomonad subclasses, new dinozoan classes Myzodinea (grouping Colpovora gen. n., Psammosa), Endodinea, Sulcodinea, and subclass Karlodinia; and ranking heterokont Gyrista as phylum not superphylum.
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6
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Moog D. In Silico Tools for the Prediction of Protein Import into Secondary Plastids. Methods Mol Biol 2018; 1829:381-394. [PMID: 29987735 DOI: 10.1007/978-1-4939-8654-5_25] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The in silico identification of proteins targeting to secondary plastids is a difficult task. Such plastids are complex in structure and can be surrounded by up to four membranes, which have to be crossed during import. Nucleus-encoded plastidial preproteins in organisms with secondary plastids contain specific N-terminal targeting signals, the so-called bipartite targeting signal (BTS) sequences consisting of a classical signal peptide followed by a transit peptide-like sequence, mediating this intricate process. As these signal sequences differ significantly from transit peptides of plastid preproteins in plants and other organisms with primary plastids, existing in silico tools for primary plastid targeting prediction are not directly suitable to detect nucleus-encoded proteins destined for the import into secondary plastids. In this chapter I describe the current state-of-the-art methods to reliably predict proteins that might be imported into secondary plastids of red- and green-algal origin using either the "classical" approach, which involves a combination of bits of information produced by existing in silico tools, or, if available, via consulting specifically developed algorithms.
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Affiliation(s)
- Daniel Moog
- Laboratory for Cell Biology, Philipps University Marburg, Marburg, Germany.
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7
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Gentil J, Hempel F, Moog D, Zauner S, Maier UG. Review: origin of complex algae by secondary endosymbiosis: a journey through time. PROTOPLASMA 2017; 254:1835-1843. [PMID: 28290059 DOI: 10.1007/s00709-017-1098-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2016] [Accepted: 03/03/2017] [Indexed: 05/19/2023]
Abstract
Secondary endosymbiosis-the merging of two eukaryotic cells into one photosynthetic cellular unit-led to the evolution of ecologically and medically very important organisms. We review the biology of these organisms, starting from the first proposal of secondary endosymbiosis up to recent phylogenetic models on the origin of secondarily evolved protists. In addition, we discuss the organelle character of the symbionts based on morphological features, gene transfers from the symbiont into the host and re-import of nucleus-encoded plastid proteins. Finally, we hypothesize that secondary endosymbiosis is more than enslaving a eukaryotic, phototrophic cell, but reflects a complex interplay between host and symbiont, leading to the inseparability of the two symbiotic partners generating a cellular entity.
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Affiliation(s)
- J Gentil
- Laboratory for Cell Biology, Philipps University Marburg, Karl-von-Frisch-Str. 8, 35032, Marburg, Germany
| | - F Hempel
- LOEWE Center for Synthetic Microbiology (Synmikro), Hans-Meerwein-Str. 6, 35032, Marburg, Germany
| | - D Moog
- Laboratory for Cell Biology, Philipps University Marburg, Karl-von-Frisch-Str. 8, 35032, Marburg, Germany
| | - S Zauner
- Laboratory for Cell Biology, Philipps University Marburg, Karl-von-Frisch-Str. 8, 35032, Marburg, Germany
| | - U G Maier
- Laboratory for Cell Biology, Philipps University Marburg, Karl-von-Frisch-Str. 8, 35032, Marburg, Germany.
- LOEWE Center for Synthetic Microbiology (Synmikro), Hans-Meerwein-Str. 6, 35032, Marburg, Germany.
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8
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A Plastid Protein That Evolved from Ubiquitin and Is Required for Apicoplast Protein Import in Toxoplasma gondii. mBio 2017; 8:mBio.00950-17. [PMID: 28655825 PMCID: PMC5487736 DOI: 10.1128/mbio.00950-17] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Apicomplexan parasites cause a variety of important infectious diseases, including malaria, toxoplasma encephalitis, and severe diarrhea due to Cryptosporidium. Most apicomplexans depend on an organelle called the apicoplast which is derived from a red algal endosymbiont. The apicoplast is essential for the parasite as the compartment of fatty acid, heme, and isoprenoid biosynthesis. The majority of the approximate 500 apicoplast proteins are nucleus encoded and have to be imported across the four membranes that surround the apicoplast. Import across the second outermost membrane of the apicoplast, the periplastid membrane, depends on an apicoplast-specific endoplasmic reticulum-associated protein degradation (ERAD) complex and on enzymes of the associated ubiquitination cascade. However, identification of an apicoplast ubiquitin associated with this machinery has long been elusive. Here we identify a plastid ubiquitin-like protein (PUBL), an apicoplast protein that is derived from a ubiquitin ancestor but that has significantly changed in its primary sequence. PUBL is distinct from known ubiquitin-like proteins, and phylogenomic analyses suggest a clade specific to apicomplexans. We demonstrate that PUBL and the AAA ATPase CDC48AP both act to translocate apicoplast proteins across the periplastid membrane during protein import. Conditional null mutants and genetic complementation show that both proteins are critical for this process and for parasite survival. PUBL residues homologous to those that are required for ubiquitin conjugation onto target proteins are essential for this function, while those required for polyubiquitination and preprotein processing are dispensable. Our experiments provide a mechanistic understanding of the molecular machinery that drives protein import across the membranes of the apicoplast. Apicomplexan parasites are responsible for important human diseases. There are no effective vaccines for use in humans, and drug treatment faces multiple challenges, including emerging resistance, lack of efficacy across the lifecycle, and adverse drug effects. The apicoplast is a promising target for novel treatments: this chloroplast-like organelle is derived from an algal symbiont, is absent from the host, and is essential for parasite growth and pathogenesis. We use Toxoplasma gondii as a model to study the apicoplast due to its strong genetic tools and established functional assays. We identify a plastid ubiquitin-like protein (PUBL) which is a novel ubiquitin-like protein and demonstrate its importance and that of the motor protein CDC48AP for apicoplast protein import. These findings broaden our understanding of the evolution and mechanistic workings of a unique parasite organelle and may lead to new opportunities for treatments against important human pathogens.
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9
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Abstract
The number and nature of endosymbioses involving red algal endosymbionts are debated. Gene phylogenies have become the most popular tool to untangle this issue, but they deliver conflicting results. As gene and lineage sampling has increased, so have both the number of conflicting trees and the number of suggestions in the literature for multiple tertiary, and even quaternary, symbioses that might reconcile the tree conflicts. Independent lines of evidence that can address the issue are needed. Here we summarize the mechanism and machinery of protein import into complex red plastids. The process involves protein translocation machinery, known as SELMA, that arose once in evolution, that facilitates protein import across the second outermost of the four plastid membranes, and that is always targeted specifically to that membrane, regardless of where it is encoded today. It is widely accepted that the unity of protein import across the two membranes of primary plastids is strong evidence for their single cyanobacterial origin. Similarly, the unity of SELMA-dependent protein import across the second outermost plastid membrane constitutes strong evidence for the existence of a single red secondary endosymbiotic event at the common origin of all red complex plastids. We furthermore propose that the two outer membranes of red complex plastids are derived from host endoplasmic reticulum in the initial red secondary endosymbiotic event.
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Affiliation(s)
- Sven B Gould
- Institute of Molecular Evolution, Heinrich-Heine University, Düsseldorf, Germany.
| | - Uwe-G Maier
- Laboratory for Cell Biology and LOEWE Centre for Synthetic Microbiology (SYNMIKRO), Phillips University, Marburg, Germany
| | - William F Martin
- Institute of Molecular Evolution, Heinrich-Heine University, Düsseldorf, Germany
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10
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Evolution of the Tetrapyrrole Biosynthetic Pathway in Secondary Algae: Conservation, Redundancy and Replacement. PLoS One 2016; 11:e0166338. [PMID: 27861576 PMCID: PMC5115734 DOI: 10.1371/journal.pone.0166338] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Accepted: 10/26/2016] [Indexed: 11/29/2022] Open
Abstract
Tetrapyrroles such as chlorophyll and heme are indispensable for life because they are involved in energy fixation and consumption, i.e. photosynthesis and oxidative phosphorylation. In eukaryotes, the tetrapyrrole biosynthetic pathway is shaped by past endosymbioses. We investigated the origins and predicted locations of the enzymes of the heme pathway in the chlorarachniophyte Bigelowiella natans, the cryptophyte Guillardia theta, the “green” dinoflagellate Lepidodinium chlorophorum, and three dinoflagellates with diatom endosymbionts (“dinotoms”): Durinskia baltica, Glenodinium foliaceum and Kryptoperidinium foliaceum. Bigelowiella natans appears to contain two separate heme pathways analogous to those found in Euglena gracilis; one is predicted to be mitochondrial-cytosolic, while the second is predicted to be plastid-located. In the remaining algae, only plastid-type tetrapyrrole synthesis is present, with a single remnant of the mitochondrial-cytosolic pathway, a ferrochelatase of G. theta putatively located in the mitochondrion. The green dinoflagellate contains a single pathway composed of mostly rhodophyte-origin enzymes, and the dinotoms hold two heme pathways of apparently plastidal origin. We suggest that heme pathway enzymes in B. natans and L. chlorophorum share a predominantly rhodophytic origin. This implies the ancient presence of a rhodophyte-derived plastid in the chlorarachniophyte alga, analogous to the green dinoflagellate, or an exceptionally massive horizontal gene transfer.
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11
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Sheiner L, Fellows JD, Ovciarikova J, Brooks CF, Agrawal S, Holmes ZC, Bietz I, Flinner N, Heiny S, Mirus O, Przyborski JM, Striepen B. Toxoplasma gondii Toc75 Functions in Import of Stromal but not Peripheral Apicoplast Proteins. Traffic 2015; 16:1254-69. [PMID: 26381927 DOI: 10.1111/tra.12333] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2015] [Revised: 09/14/2015] [Accepted: 09/14/2015] [Indexed: 01/09/2023]
Abstract
Apicomplexa are unicellular parasites causing important human and animal diseases, including malaria and toxoplasmosis. Most of these pathogens possess a relict but essential plastid, the apicoplast. The apicoplast was acquired by secondary endosymbiosis between a red alga and a flagellated eukaryotic protist. As a result the apicoplast is surrounded by four membranes. This complex structure necessitates a system of transport signals and translocons allowing nuclear encoded proteins to find their way to specific apicoplast sub-compartments. Previous studies identified translocons traversing two of the four apicoplast membranes. Here we provide functional support for the role of an apicomplexan Toc75 homolog in apicoplast protein transport. We identify two apicomplexan genes encoding Toc75 and Sam50, both members of the Omp85 protein family. We localize the respective proteins to the apicoplast and the mitochondrion of Toxoplasma and Plasmodium. We show that the Toxoplasma Toc75 is essential for parasite growth and that its depletion results in a rapid defect in the import of apicoplast stromal proteins while the import of proteins of the outer compartments is affected only as the secondary consequence of organelle loss. These observations along with the homology to Toc75 suggest a potential role in transport through the second innermost membrane.
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Affiliation(s)
- Lilach Sheiner
- Center for Tropical and Emerging Global Diseases & Department of Cellular Biology, University of Georgia, 500 D.W. Brooks Drive, Athens, GA, 30602, USA.,Wellcome Trust Centre For Molecular Parasitology, Institute of Infection, Immunity & Inflammation, College of Medical, Veterinary & Life Sciences, Sir Graeme Davies Building, University of Glasgow, 120 University Place, Glasgow, G12 8TA, UK
| | - Justin D Fellows
- Center for Tropical and Emerging Global Diseases & Department of Cellular Biology, University of Georgia, 500 D.W. Brooks Drive, Athens, GA, 30602, USA
| | - Jana Ovciarikova
- Wellcome Trust Centre For Molecular Parasitology, Institute of Infection, Immunity & Inflammation, College of Medical, Veterinary & Life Sciences, Sir Graeme Davies Building, University of Glasgow, 120 University Place, Glasgow, G12 8TA, UK
| | - Carrie F Brooks
- Center for Tropical and Emerging Global Diseases & Department of Cellular Biology, University of Georgia, 500 D.W. Brooks Drive, Athens, GA, 30602, USA
| | - Swati Agrawal
- Center for Tropical and Emerging Global Diseases & Department of Cellular Biology, University of Georgia, 500 D.W. Brooks Drive, Athens, GA, 30602, USA
| | - Zachary C Holmes
- Center for Tropical and Emerging Global Diseases & Department of Cellular Biology, University of Georgia, 500 D.W. Brooks Drive, Athens, GA, 30602, USA
| | - Irine Bietz
- Department of Parasitology, Faculty of Biology, Philipps University Marburg, Marburg, Germany
| | - Nadine Flinner
- Molecular Cell Biology of Plants, Biocenter N200, 3. OG, Max-von-Laue-Str. 9, 60438, Frankfurt, Germany
| | - Sabrina Heiny
- Department of Parasitology, Faculty of Biology, Philipps University Marburg, Marburg, Germany
| | - Oliver Mirus
- Molecular Cell Biology of Plants, Biocenter N200, 3. OG, Max-von-Laue-Str. 9, 60438, Frankfurt, Germany
| | - Jude M Przyborski
- Department of Parasitology, Faculty of Biology, Philipps University Marburg, Marburg, Germany
| | - Boris Striepen
- Center for Tropical and Emerging Global Diseases & Department of Cellular Biology, University of Georgia, 500 D.W. Brooks Drive, Athens, GA, 30602, USA
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12
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Hehenberger E, Imanian B, Burki F, Keeling PJ. Evidence for the retention of two evolutionary distinct plastids in dinoflagellates with diatom endosymbionts. Genome Biol Evol 2015; 6:2321-34. [PMID: 25172904 PMCID: PMC4217693 DOI: 10.1093/gbe/evu182] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Dinoflagellates harboring diatom endosymbionts (termed “dinotoms”) have undergone a process often referred to as “tertiary endosymbiosis”—the uptake of algae containing secondary plastids and integration of those plastids into the new host. In contrast to other tertiary plastids, and most secondary plastids, the endosymbiont of dinotoms is distinctly less reduced, retaining a number of cellular features, such as their nucleus and mitochondria and others, in addition to their plastid. This has resulted in redundancy between host and endosymbiont, at least between some mitochondrial and cytosolic metabolism, where this has been investigated. The question of plastidial redundancy is particularly interesting as the fate of the host dinoflagellate plastid is unclear. The host cytosol possesses an eyespot that has been postulated to be a remnant of the ancestral peridinin plastid, but this has not been tested, nor has its possible retention of plastid functions. To investigate this possibility, we searched for plastid-associated pathways and functions in transcriptomic data sets from three dinotom species. We show that the dinoflagellate host has indeed retained genes for plastid-associated pathways and that these genes encode targeting peptides similar to those of other dinoflagellate plastid-targeted proteins. Moreover, we also identified one gene encoding an essential component of the dinoflagellate plastid protein import machinery, altogether suggesting the presence of a functioning plastid import system in the host, and by extension a relict plastid. The presence of the same plastid-associated pathways in the endosymbiont also extends the known functional redundancy in dinotoms, further confirming the unusual state of plastid integration in this group of dinoflagellates.
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Affiliation(s)
- Elisabeth Hehenberger
- Department of Botany, Canadian Institute for Advanced Research, University of British Columbia, Vancouver, British Columbia, Canada
| | - Behzad Imanian
- Department of Botany, Canadian Institute for Advanced Research, University of British Columbia, Vancouver, British Columbia, Canada
| | - Fabien Burki
- Department of Botany, Canadian Institute for Advanced Research, University of British Columbia, Vancouver, British Columbia, Canada
| | - Patrick J Keeling
- Department of Botany, Canadian Institute for Advanced Research, University of British Columbia, Vancouver, British Columbia, Canada
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Abstract
Many protists with high ecological and medical relevance harbor plastids surrounded by four membranes. Thus, nucleus-encoded proteins of these complex plastids have to traverse these barriers. Here we report on the identification of the protein translocators located in two of the plastid surrounding membranes and present recent findings on the mechanisms of protein import into the plastids of diatoms.
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Abstract
The endosymbiotic origin of plastids from cyanobacteria was a landmark event in the history of eukaryotic life. Subsequent to the evolution of primary plastids, photosynthesis spread from red and green algae to unrelated eukaryotes by secondary and tertiary endosymbiosis. Although the movement of cyanobacterial genes from endosymbiont to host is well studied, less is known about the migration of eukaryotic genes from one nucleus to the other in the context of serial endosymbiosis. Here I explore the magnitude and potential impact of nucleus-to-nucleus endosymbiotic gene transfer in the evolution of complex algae, and the extent to which such transfers compromise our ability to infer the deep structure of the eukaryotic tree of life. In addition to endosymbiotic gene transfer, horizontal gene transfer events occurring before, during, and after endosymbioses further confound our efforts to reconstruct the ancient mergers that forged multiple lines of photosynthetic microbial eukaryotes.
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15
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Lau JB, Stork S, Moog D, Sommer MS, Maier UG. N-terminal lysines are essential for protein translocation via a modified ERAD system in complex plastids. Mol Microbiol 2015; 96:609-20. [PMID: 25644868 DOI: 10.1111/mmi.12959] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/01/2015] [Indexed: 01/01/2023]
Abstract
Nuclear-encoded pre-proteins being imported into complex plastids of red algal origin have to cross up to five membranes. Thereby, transport across the second outermost or periplastidal membrane (PPM) is facilitated by SELMA (symbiont-specific ERAD-like machinery), an endoplasmic reticulum-associated degradation (ERAD)-derived machinery. Core components of SELMA are enzymes involved in ubiquitination (E1-E3), a Cdc48 ATPase complex and Derlin proteins. These components are present in all investigated organisms with four membrane-bound complex plastids of red algal origin, suggesting a ubiquitin-dependent translocation process of substrates mechanistically similar to the process of retro-translocation in ERAD. Even if, according to the current model, translocation via SELMA does not end up in the classical poly-ubiquitination, transient mono-/oligo-ubiquitination of pre-proteins might be required for the mechanism of translocation. We investigated the import mechanism of SELMA and were able to show that protein transport across the PPM depends on lysines in the N-terminal but not in the C-terminal part of pre-proteins. These lysines are predicted to be targets of ubiquitination during the translocation process. As proteins lacking the N-terminal lysines get stuck in the PPM, a 'frozen intermediate' of the translocation process could be envisioned and initially characterized.
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Affiliation(s)
- Julia B Lau
- Laboratory for Cell Biology, Philipps Universität Marburg, Karl-von-Frisch Str. 8, D-35043, Marburg, Germany
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16
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The periplastidal compartment: a naturally minimized eukaryotic cytoplasm. Curr Opin Microbiol 2014; 22:88-93. [DOI: 10.1016/j.mib.2014.09.017] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2014] [Revised: 09/15/2014] [Accepted: 09/24/2014] [Indexed: 11/24/2022]
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17
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Zimorski V, Ku C, Martin WF, Gould SB. Endosymbiotic theory for organelle origins. Curr Opin Microbiol 2014; 22:38-48. [PMID: 25306530 DOI: 10.1016/j.mib.2014.09.008] [Citation(s) in RCA: 217] [Impact Index Per Article: 21.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2014] [Revised: 09/01/2014] [Accepted: 09/12/2014] [Indexed: 11/19/2022]
Abstract
Endosymbiotic theory goes back over 100 years. It explains the similarity of chloroplasts and mitochondria to free-living prokaryotes by suggesting that the organelles arose from prokaryotes through (endo)symbiosis. Gene trees provide important evidence in favour of symbiotic theory at a coarse-grained level, but the finer we get into the details of branches in trees containing dozens or hundreds of taxa, the more equivocal evidence for endosymbiotic events sometimes becomes. It seems that either the interpretation of some endosymbiotic events are wrong, or something is wrong with the interpretations of some gene trees having many leaves. There is a need for evidence that is independent of gene trees and that can help outline the course of symbiosis in eukaryote evolution. Protein import is the strongest evidence we have for the single origin of chloroplasts and mitochondria. It is probably also the strongest evidence we have to sort out the number and nature of secondary endosymbiotic events that have occurred in evolution involving the red plastid lineage. If we relax our interpretation of individual gene trees, endosymbiotic theory can tell us a lot.
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Affiliation(s)
- Verena Zimorski
- Institute of Molecular Evolution, Heinrich-Heine-University of Düsseldorf, 40225 Düsseldorf, Germany
| | - Chuan Ku
- Institute of Molecular Evolution, Heinrich-Heine-University of Düsseldorf, 40225 Düsseldorf, Germany
| | - William F Martin
- Institute of Molecular Evolution, Heinrich-Heine-University of Düsseldorf, 40225 Düsseldorf, Germany.
| | - Sven B Gould
- Institute of Molecular Evolution, Heinrich-Heine-University of Düsseldorf, 40225 Düsseldorf, Germany
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Hovde BT, Starkenburg SR, Hunsperger HM, Mercer LD, Deodato CR, Jha RK, Chertkov O, Monnat RJ, Cattolico RA. The mitochondrial and chloroplast genomes of the haptophyte Chrysochromulina tobin contain unique repeat structures and gene profiles. BMC Genomics 2014; 15:604. [PMID: 25034814 PMCID: PMC4226036 DOI: 10.1186/1471-2164-15-604] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2014] [Accepted: 07/09/2014] [Indexed: 01/22/2023] Open
Abstract
BACKGROUND Haptophytes are widely and abundantly distributed in both marine and freshwater ecosystems. Few genomic analyses of representatives within this taxon have been reported, despite their early evolutionary origins and their prominent role in global carbon fixation. RESULTS The complete mitochondrial and chloroplast genome sequences of the haptophyte Chrysochromulina tobin (Prymnesiales) provide insight into the architecture and gene content of haptophyte organellar genomes. The mitochondrial genome (~34 kb) encodes 21 protein coding genes and contains a complex, 9 kb tandem repeat region. Similar to other haptophytes and rhodophytes, but not cryptophytes or stramenopiles, the mitochondrial genome has lost the nad7, nad9 and nad11 genes. The ~105 kb chloroplast genome encodes 112 protein coding genes, including ycf39 which has strong structural homology to NADP-binding nitrate transcriptional regulators; a divergent 'CheY-like' two-component response regulator (ycf55) and Tic/Toc (ycf60 and ycf80) membrane transporters. Notably, a zinc finger domain has been identified in the rpl36 ribosomal protein gene of all chloroplasts sequenced to date with the exception of haptophytes and cryptophytes--algae that have gained (via lateral gene transfer) an alternative rpl36 lacking the zinc finger motif. The two C. tobin chloroplast ribosomal RNA operon spacer regions differ in tRNA content. Additionally, each ribosomal operon contains multiple single nucleotide polymorphisms (SNPs)--a pattern observed in rhodophytes and cryptophytes, but few stramenopiles. Analysis of small (<200 bp) chloroplast encoded tandem and inverted repeats in C. tobin and 78 other algal chloroplast genomes show that repeat type, size and location are correlated with gene identity and taxonomic clade. CONCLUSION The Chrysochromulina tobin organellar genomes provide new insight into organellar function and evolution. These are the first organellar genomes to be determined for the prymnesiales, a taxon that is present in both oceanic and freshwater systems and represents major primary photosynthetic producers and contributors to global ecosystem stability.
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Stork S, Lau J, Moog D, Maier UG. Three old and one new: protein import into red algal-derived plastids surrounded by four membranes. PROTOPLASMA 2013; 250:1013-1023. [PMID: 23612938 DOI: 10.1007/s00709-013-0498-7] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2013] [Accepted: 04/08/2013] [Indexed: 06/02/2023]
Abstract
Engulfment of a red or green alga by another eukaryote and subsequent reduction of the symbiont to an organelle, termed a complex plastid, is a process known as secondary endosymbiosis and is shown in a diverse group of eukaryotic organisms. Important members are heterokontophytes, haptophytes, cryptophytes, and apicomplexan parasites, all of them with complex plastids of red algal origin surrounded by four membranes. Although the evolutionary relationship between these organisms is still debated, they share common mechanisms for plastid protein import. In this review, we describe recent findings and current models on preprotein import into complex plastids with a special focus on the second outermost plastid membrane. Derived from the plasma membrane of the former endosymbiont, the evolution of protein transport across this so-called periplastidal membrane most likely represented the challenge in the transition from an endosymbiont to a host-dependent organelle. Here, remodeling and relocation of the symbiont endoplasmic reticulum-associated degradation (ERAD) machinery gave rise to a translocon complex termed symbiont-specific ERAD-like machinery and provides a fascinating insight into complex cellular evolution.
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Affiliation(s)
- Simone Stork
- Laboratory for Cell Biology, Philipps-Universität Marburg, Karl-von-Frisch Str.8, 35032, Marburg, Germany
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20
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Peschke M, Hempel F. Glycoprotein import: a common feature of complex plastids? PLANT SIGNALING & BEHAVIOR 2013; 8:26050. [PMID: 24220152 PMCID: PMC4091080 DOI: 10.4161/psb.26050] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2013] [Accepted: 08/05/2013] [Indexed: 06/02/2023]
Abstract
Complex plastids evolved by secondary endosymbiosis and are, in contrast to primary plastids, surrounded by 3 or 4 envelope membranes. Recently, we provided evidence that in diatoms proteins exist that get N-glycosylated during transport across the outermost membrane of the complex plastid. This gives rise to unique questions on the transport mechanisms of these bulky proteins, which get transported across up to 3 further membranes into the plastid stroma. Here we discuss our results in an evolutionary context and speculate about the existence of plastidal glycoproteins in other organisms with complex plastids.
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Affiliation(s)
- Madeleine Peschke
- Department of Cell Biology of the Philipps University Marburg; Marburg, Germany
- Current Affiliation: Department of Biomolecular Mechanisms; Max-Planck-Institute for Medical Research; Heidelberg, Germany
| | - Franziska Hempel
- LOEWE Centre for Synthetic Microbiology (SYNMIKRO); Marburg, Germany
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21
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Hopkins JF, Spencer DF, Laboissiere S, Neilson JAD, Eveleigh RJM, Durnford DG, Gray MW, Archibald JM. Proteomics reveals plastid- and periplastid-targeted proteins in the chlorarachniophyte alga Bigelowiella natans. Genome Biol Evol 2013; 4:1391-406. [PMID: 23221610 PMCID: PMC3542566 DOI: 10.1093/gbe/evs115] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Chlorarachniophytes are unicellular marine algae with plastids (chloroplasts) of secondary endosymbiotic origin. Chlorarachniophyte cells retain the remnant nucleus (nucleomorph) and cytoplasm (periplastidial compartment, PPC) of the green algal endosymbiont from which their plastid was derived. To characterize the diversity of nucleus-encoded proteins targeted to the chlorarachniophyte plastid, nucleomorph, and PPC, we isolated plastid–nucleomorph complexes from the model chlorarachniophyte Bigelowiella natans and subjected them to high-pressure liquid chromatography-tandem mass spectrometry. Our proteomic analysis, the first of its kind for a nucleomorph-bearing alga, resulted in the identification of 324 proteins with 95% confidence. Approximately 50% of these proteins have predicted bipartite leader sequences at their amino termini. Nucleus-encoded proteins make up >90% of the proteins identified. With respect to biological function, plastid-localized light-harvesting proteins were well represented, as were proteins involved in chlorophyll biosynthesis. Phylogenetic analyses revealed that many, but by no means all, of the proteins identified in our proteomic screen are of apparent green algal ancestry, consistent with the inferred evolutionary origin of the plastid and nucleomorph in chlorarachniophytes.
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Affiliation(s)
- Julia F Hopkins
- Department of Biochemistry and Molecular Biology, Dalhousie University, Nova Scotia, Canada
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Keeling PJ. The number, speed, and impact of plastid endosymbioses in eukaryotic evolution. ANNUAL REVIEW OF PLANT BIOLOGY 2013; 64:583-607. [PMID: 23451781 DOI: 10.1146/annurev-arplant-050312-120144] [Citation(s) in RCA: 265] [Impact Index Per Article: 24.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Plastids (chloroplasts) have long been recognized to have originated by endosymbiosis of a cyanobacterium, but their subsequent evolutionary history has proved complex because they have also moved between eukaryotes during additional rounds of secondary and tertiary endosymbioses. Much of this history has been revealed by genomic analyses, but some debates remain unresolved, in particular those relating to secondary red plastids of the chromalveolates, especially cryptomonads. Here, I examine several fundamental questions and assumptions about endosymbiosis and plastid evolution, including the number of endosymbiotic events needed to explain plastid diversity, whether the genetic contribution of the endosymbionts to the host genome goes far beyond plastid-targeted genes, and whether organelle origins are best viewed as a singular transition involving one symbiont or as a gradual transition involving a long line of transient food/symbionts. I also discuss a possible link between transporters and the evolution of protein targeting in organelle integration.
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Affiliation(s)
- Patrick J Keeling
- Canadian Institute for Advanced Research and Department of Botany, University of British Columbia, Vancouver, Canada V6T 1Z4.
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Sheiner L, Striepen B. Protein sorting in complex plastids. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2012; 1833:352-9. [PMID: 22683761 DOI: 10.1016/j.bbamcr.2012.05.030] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2012] [Revised: 05/25/2012] [Accepted: 05/28/2012] [Indexed: 12/11/2022]
Abstract
Taming a cyanobacterium in a pivitol event of endosymbiosis brought photosynthesis to eukaryotes, and gave rise to the plastids found in glaucophytes, red and green algae, and the descendants of the latter, the plants. Ultrastructural as well as molecular research over the last two decades has demonstrated that plastids have enjoyed surprising lateral mobility across the tree of life. Numerous independent secondary and tertiary endosymbiosis have led to a spread of plastids into a variety of, up to that point, non-photosynthetic lineages. Happily eating and subsequently domesticating one another protists conquered a wide variety of ecological niches. The elaborate evolution of secondary, or complex, plastids is reflected in the numerous membranes that bound them (three or four compared to the two membranes of the primary plastids). Gene transfer to the host nucleus is a hallmark of endosymbiosis and provides centralized cellular control. Here we review how these proteins find their way back into the stroma of the organelle and describe the advances in the understanding of the molecular mechanisms that allow protein translocation across four membranes. This article is part of a Special Issue entitled: Protein Import and Quality Control in Mitochondria and Plastids.
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Affiliation(s)
- Lilach Sheiner
- Center for Tropical and Emerging Global Diseases & Department of Cellular Biology, University of Georgia, 500 D.W. Brooks Drive, Athens, GA 30602, USA.
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