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Ban H, Sato S, Yoshikawa S, Yamada K, Nakamura Y, Ichinomiya M, Sato N, Blanc-Mathieu R, Endo H, Kuwata A, Ogata H. Genome analysis of Parmales, the sister group of diatoms, reveals the evolutionary specialization of diatoms from phago-mixotrophs to photoautotrophs. Commun Biol 2023; 6:697. [PMID: 37420035 PMCID: PMC10328945 DOI: 10.1038/s42003-023-05002-x] [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: 10/13/2022] [Accepted: 05/31/2023] [Indexed: 07/09/2023] Open
Abstract
The order Parmales (class Bolidophyceae) is a minor group of pico-sized eukaryotic marine phytoplankton that contains species with cells surrounded by silica plates. Previous studies revealed that Parmales is a member of ochrophytes and sister to diatoms (phylum Bacillariophyta), the most successful phytoplankton group in the modern ocean. Therefore, parmalean genomes can serve as a reference to elucidate both the evolutionary events that differentiated these two lineages and the genomic basis for the ecological success of diatoms vs. the more cryptic lifestyle of parmaleans. Here, we compare the genomes of eight parmaleans and five diatoms to explore their physiological and evolutionary differences. Parmaleans are predicted to be phago-mixotrophs. By contrast, diatoms have lost genes related to phagocytosis, indicating the ecological specialization from phago-mixotrophy to photoautotrophy in their early evolution. Furthermore, diatoms show significant enrichment in gene sets involved in nutrient uptake and metabolism, including iron and silica, in comparison with parmaleans. Overall, our results suggest a strong evolutionary link between the loss of phago-mixotrophy and specialization to a silicified photoautotrophic life stage early in diatom evolution after diverging from the Parmales lineage.
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Affiliation(s)
- Hiroki Ban
- Bioinformatics Center, Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto, 611-0011, Japan
| | - Shinya Sato
- Department of Marine Science and Technology, Fukui Prefectural University, 1-1 Gakuen-cho, Obama City, Fukui, 917-0003, Japan
| | - Shinya Yoshikawa
- Department of Marine Science and Technology, Fukui Prefectural University, 1-1 Gakuen-cho, Obama City, Fukui, 917-0003, Japan
| | - Kazumasa Yamada
- Department of Marine Science and Technology, Fukui Prefectural University, 1-1 Gakuen-cho, Obama City, Fukui, 917-0003, Japan
| | - Yoji Nakamura
- Bioinformatics and Biosciences Division, Fisheries Stock Assessment Center, Fisheries Resources Institute, Japan Fisheries Research and Education Agency, 2-12-4 Fuku-ura, Kanazawa, Yokohama, Kanagawa, 236-8648, Japan
| | - Mutsuo Ichinomiya
- Prefectural University of Kumamoto, 3-1-100 Tsukide, Kumamoto, 862-8502, Japan
| | - Naoki Sato
- Graduate School of Arts and Sciences, University of Tokyo, Komaba, Meguro-ku, Tokyo, 153-8902, Japan
| | - Romain Blanc-Mathieu
- Bioinformatics Center, Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto, 611-0011, Japan
- Laboratoire de Physiologie Cellulaire & Végétale, CEA, Univ. Grenoble Alpes, CNRS, INRA, IRIG, Grenoble, France
| | - Hisashi Endo
- Bioinformatics Center, Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto, 611-0011, Japan
| | - Akira Kuwata
- Shiogama field station, Fisheries Resources Institute, Japan Fisheries Research and Education Agency, 3-27-5 Shinhama-cho, Shiogama, Miyagi, Japan.
| | - Hiroyuki Ogata
- Bioinformatics Center, Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto, 611-0011, Japan.
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Liu F, Wang Y, Huang H, Chen N. Evolutionary dynamics of plastomes in coscinodiscophycean diatoms revealed by comparative genomics. Front Microbiol 2023; 14:1203780. [PMID: 37396366 PMCID: PMC10307964 DOI: 10.3389/fmicb.2023.1203780] [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: 04/11/2023] [Accepted: 06/01/2023] [Indexed: 07/04/2023] Open
Abstract
To understand the evolution of coscinodiscophycean diatoms, plastome sequences of six coscinodiscophycean diatom species were constructed and analyzed in this study, doubling the number of constructed plastome sequences in Coscinodiscophyceae (radial centrics). The platome sizes varied substantially in Coscinodiscophyceae, ranging from 119.1 kb of Actinocyclus subtilis to 135.8 kb of Stephanopyxis turris. Plastomes in Paraliales and Stephanopyxales tended to be larger than those in Rhizosoleniales and Coscinodiacales, which were due to the expansion of the inverted repeats (IRs) and to the marked increase of the large single copy (LSC). Phylogenomic analysis indicated that Paralia and Stephanopyxis clustered tightly to form the Paraliales-Stephanopyxales complex, which was sister to the Rhizosoleniales-Coscinodiscales complex. The divergence time between Paraliales and Stephanopyxales was estimated at 85 MYA in the middle Upper Cretaceous, indicating that Paraliales and Stephanopyxales appeared later than Coscinodiacales and Rhizosoleniales according to their phylogenetic relationships. Frequent losses of housekeeping protein-coding genes (PCGs) were observed in these coscinodiscophycean plastomes, indicating that diatom plastomes showed an ongoing reduction in gene content during evolution. Two acpP genes (acpP1 and acpP2) detected in diatom plastomes were found to be originated from an early gene duplication event occurred in the common progenitor after diatom emergence, rather than multiple independent gene duplications occurring in different lineages of diatoms. The IRs in Stephanopyxis turris and Rhizosolenia fallax-imbricata exhibited a similar trend of large expansion to the small single copy (SSC) and slightly small contraction from the LSC, which eventually led to the conspicuous increase in IR size. Gene order was highly conserved in Coscinodiacales, while multiple rearrangements were observed in Rhizosoleniales and between Paraliales and Stephanopyxales. Our results greatly expanded the phylogenetic breadth in Coscinodiscophyceae and gained novel insights into the evolution of plastomes in diatoms.
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Affiliation(s)
- Feng Liu
- CAS Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, Shandong, China
- Marine Ecology and Environmental Science Laboratory, Laoshan Laboratory, Qingdao, Shandong, China
- Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao, Shandong, China
| | - Yichao Wang
- Chinese Academy of Fishery Sciences, Beijing, China
| | - Hailong Huang
- School of Marine Sciences, Ningbo University, Ningbo, Zhejiang, China
| | - Nansheng Chen
- CAS Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, Shandong, China
- Marine Ecology and Environmental Science Laboratory, Laoshan Laboratory, Qingdao, Shandong, China
- Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao, Shandong, China
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3
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Zhang M, Chen N. Comparative analysis of Thalassionema chloroplast genomes revealed hidden biodiversity. BMC Genomics 2022; 23:327. [PMID: 35477350 PMCID: PMC9044688 DOI: 10.1186/s12864-022-08532-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2021] [Accepted: 04/04/2022] [Indexed: 11/22/2022] Open
Abstract
The cosmopolitan Thalassionema species are often dominant components of the plankton diatom flora and sediment diatom assemblages in all but the Polar regions, making important ecological contribution to primary productivity. Historical studies concentrated on their indicative function for the marine environment based primarily on morphological features and essentially ignored their genomic information, hindering in-depth investigation on Thalassionema biodiversity. In this project, we constructed the complete chloroplast genomes (cpDNAs) of seven Thalassionema strains representing three different species, which were also the first cpDNAs constructed for any species in the order Thalassionematales that includes 35 reported species and varieties. The sizes of these Thalassionema cpDNAs, which showed typical quadripartite structures, varied from 124,127 bp to 140,121 bp. Comparative analysis revealed that Thalassionema cpDNAs possess conserved gene content inter-species and intra-species, along with several gene losses and transfers. Besides, their cpDNAs also have expanded inverted repeat regions (IRs) and preserve large intergenic spacers compared to other diatom cpDNAs. In addition, substantial genome rearrangements were discovered not only among different Thalassionema species but also among strains of a same species T. frauenfeldii, suggesting much higher diversity than previous reports. In addition to confirming the phylogenetic position of Thalassionema species, this study also estimated their emergence time at approximately 38 Mya. The availability of the Thalassionema species cpDNAs not only helps understand the Thalassionema species, but also facilitates phylogenetic analysis of diatoms.
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Affiliation(s)
- Mengjia Zhang
- CAS Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, 266071, China.,Laboratory of Marine Ecology and Environmental Science, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266200, China.,College of Marine Science, University of Chinese Academy of Sciences, Beijing, 10039, China.,Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao, 266071, China
| | - Nansheng Chen
- CAS Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, 266071, China. .,Laboratory of Marine Ecology and Environmental Science, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266200, China. .,Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao, 266071, China. .,Department of Molecular Biology and Biochemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC, V5A 1S6, Canada.
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4
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Gann ER, Truchon AR, Papoulis SE, Dyhrman ST, Gobler CJ, Wilhelm SW. Aureococcus anophagefferens (Pelagophyceae) genomes improve evaluation of nutrient acquisition strategies involved in brown tide dynamics. JOURNAL OF PHYCOLOGY 2022; 58:146-160. [PMID: 34773248 DOI: 10.1111/jpy.13221] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Revised: 10/29/2021] [Accepted: 11/02/2021] [Indexed: 06/13/2023]
Abstract
The pelagophyte Aureococcus anophagefferens causes harmful brown tide blooms in marine embayments on three continents. Aureococcus anophagefferens was the first harmful algal bloom species to have its genome sequenced, an advance that evidenced genes important for adaptation to environmental conditions that prevail during brown tides. To expand the genomic tools available for this species, genomes for four strains were assembled, including three newly sequenced strains and one assembled from publicly available data. These genomes ranged from 57.11 to 73.62 Mb, encoding 13,191-17,404 potential proteins. All strains shared ~90% of their encoded proteins as determined by homology searches and shared most functional orthologs as determined by KEGG, although each strain also possessed coding sequences with unique functions. Like the original reference genome, the genomes assembled in this study possessed genes hypothesized to be important in bloom proliferation, including genes involved in organic compound metabolism and growth at low light. Cross-strain informatics and culture experiments suggest that the utilization of purines is a potentially important source of organic nitrogen for brown tides. Analyses of metatranscriptomes from a brown tide event demonstrated that use of a single genome yielded a lower read mapping percentage (~30% of library reads) as compared to a database generated from all available genomes (~43%), suggesting novel information about bloom ecology can be gained from expanding genomic space. This work demonstrates the continued need to sequence ecologically relevant algae to understand the genomic potential and their ecology in the environment.
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Affiliation(s)
- Eric R Gann
- Department of Microbiology, University of Tennessee, Knoxville, Tennessee, 37996, USA
| | - Alexander R Truchon
- Department of Microbiology, University of Tennessee, Knoxville, Tennessee, 37996, USA
| | - Spiridon E Papoulis
- Department of Microbiology, University of Tennessee, Knoxville, Tennessee, 37996, USA
| | - Sonya T Dyhrman
- Biology and Paleo Environment Division, Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York, 10964, USA
- Department of Earth and Environmental Sciences, Columbia University, Palisades, New York, 10964, USA
| | - Christopher J Gobler
- School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, New York, 11790, USA
| | - Steven W Wilhelm
- Department of Microbiology, University of Tennessee, Knoxville, Tennessee, 37996, USA
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5
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Spatiotemporal Variations in Antarctic Protistan Communities Highlight Phytoplankton Diversity and Seasonal Dominance by a Novel Cryptophyte Lineage. mBio 2021; 12:e0297321. [PMID: 34903046 PMCID: PMC8669470 DOI: 10.1128/mbio.02973-21] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
The Andvord fjord in the West Antarctic Peninsula (WAP) is known for its productivity and abundant megafauna. Nevertheless, seasonal patterns of the molecular diversity and abundance of protistan community members underpinning WAP productivity remain poorly resolved. We performed spring and fall expeditions pursuing protistan diversity, abundance of photosynthetic taxa, and the connection to changing conditions. 18S rRNA amplicon sequence variant (ASV) profiles revealed diverse predatory protists spanning multiple eukaryotic supergroups, alongside enigmatic heterotrophs like the Picozoa. Among photosynthetic protists, cryptophyte contributions were notable. Analysis of plastid-derived 16S rRNA ASVs supported 18S ASV results, including a dichotomy between cryptophytes and diatom contributions previously reported in other Antarctic regions. We demonstrate that stramenopile and cryptophyte community structures have distinct attributes. Photosynthetic stramenopiles exhibit high diversity, with the polar diatom Fragilariopsis cylindrus, unidentified Chaetoceros species, and others being prominent. Conversely, ASV analyses followed by environmental full-length rRNA gene sequencing, electron microscopy, and flow cytometry revealed that a novel alga dominates the cryptophytes. Phylogenetic analyses established that TPG clade VII, as named here, is evolutionarily distinct from cultivated cryptophyte lineages. Additionally, cryptophyte cell abundance correlated with increased water temperature. Analyses of global data sets showed that clade VII dominates cryptophyte ASVs at Southern Ocean sites and appears to be endemic, whereas in the Arctic and elsewhere, Teleaulax amphioxeia and Plagioselmis prolonga dominate, although both were undetected in Antarctic waters. Collectively, our studies provide baseline data against which future change can be assessed, identify different diversification patterns between stramenopiles and cryptophytes, and highlight an evolutionarily distinct cryptophyte clade that thrives under conditions enhanced by warming.
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Barcytė D, Eikrem W, Engesmo A, Seoane S, Wohlmann J, Horák A, Yurchenko T, Eliáš M. Olisthodiscus represents a new class of Ochrophyta. JOURNAL OF PHYCOLOGY 2021; 57:1094-1118. [PMID: 33655496 DOI: 10.1111/jpy.13155] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Revised: 12/08/2020] [Accepted: 01/04/2021] [Indexed: 06/12/2023]
Abstract
The phylogenetic diversity of Ochrophyta, a diverse and ecologically important radiation of algae, is still incompletely understood even at the level of the principal lineages. One taxon that has eluded simple classification is the marine flagellate genus Olisthodiscus. We investigated Olisthodiscus luteus K-0444 and documented its morphological and genetic differences from the NIES-15 strain, which we described as Olisthodiscus tomasii sp. nov. Phylogenetic analyses of combined 18S and 28S rRNA sequences confirmed that Olisthodiscus constitutes a separate, deep, ochrophyte lineage, but its position could not be resolved. To overcome this problem, we sequenced the plastid genome of O. luteus K-0444 and used the new data in multigene phylogenetic analyses, which suggested that Olisthodiscus is a sister lineage of the class Pinguiophyceae within a broader clade additionally including Chrysophyceae, Synchromophyceae, and Eustigmatophyceae. Surprisingly, the Olisthodiscus plastid genome contained three genes, ycf80, cysT, and cysW, inherited from the rhodophyte ancestor of the ochrophyte plastid yet lost from all other ochrophyte groups studied so far. Combined with nuclear genes for CysA and Sbp proteins, Olisthodiscus is the only known ochrophyte possessing a plastidial sulfate transporter SulT. In addition, the finding of a cemA gene in the Olisthodiscus plastid genome and an updated phylogenetic analysis ruled out the previously proposed hypothesis invoking horizontal cemA transfer from a green algal plastid into Synurales. Altogether, Olisthodiscus clearly represents a novel phylogenetically distinct ochrophyte lineage, which we have proposed as a new class, Olisthodiscophyceae.
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Affiliation(s)
- Dovilė Barcytė
- Department of Biology and Ecology, Faculty of Science, University of Ostrava, 710 00, Ostrava, Czech Republic
| | - Wenche Eikrem
- Norwegian Institute for Water Research, Gaustadallèen 21, 0349, Oslo, Norway
- Natural history Museum, University of Oslo, P.O. Box 1172 Blindern, 0318, Oslo, Norway
- Department of Biosciences, University of Oslo, P.O. Box 1066 Blindern, 0316, Oslo, Norway
| | - Anette Engesmo
- Norwegian Institute for Water Research, Gaustadallèen 21, 0349, Oslo, Norway
- Department of Biosciences, University of Oslo, P.O. Box 1066 Blindern, 0316, Oslo, Norway
| | - Sergio Seoane
- Department of Plant Biology and Ecology, University of the Basque Country (UPV/EHU), 48940, Leioa, Spain
| | - Jens Wohlmann
- Department of Biosciences, University of Oslo, P.O. Box 1066 Blindern, 0316, Oslo, Norway
| | - Aleš Horák
- Biology Centre, Czech Academy of Sciences, Institute of Parasitology, Branišovská 31, 37005, České Budějovice, Czech Republic
- Department of Molecular Biology, Faculty of Science, University of South Bohemia, Branišovská 31, 37005, České Budějovice, Czech Republic
| | - Tatiana Yurchenko
- Department of Biology and Ecology, Faculty of Science, University of Ostrava, 710 00, Ostrava, Czech Republic
| | - Marek Eliáš
- Department of Biology and Ecology, Faculty of Science, University of Ostrava, 710 00, Ostrava, Czech Republic
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7
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Yao Y, Liu F, Chen N. Complete mitochondrial genome of Rhizosolenia setigera (Coscinodiscophyceae, Bacillariophyta). MITOCHONDRIAL DNA PART B-RESOURCES 2021; 6:2319-2321. [PMID: 34291170 PMCID: PMC8279148 DOI: 10.1080/23802359.2021.1950059] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Rhizosolenia is a species-rich genus with 144 described species, many of which are harmful algal species (HABs) with significant negative ecological impact. Despite their significance in primary production and their potential to induce HABs, genome data of these species remain extremely limited. In this study, the complete mitochondrial genome (mtDNA) of Rhizosolenia setigera Brightwell 1858 was determined for the first time, which also represented the first mtDNA of the order Rhizosoleniales. The circular mtDNA was 34,792 bp in length with GC content of 23.28%. It encoded 63 genes including 35 protein-coding genes (PCGs), 24 transfer RNA (tRNA) genes, 2 ribosomal RNA (rRNA) genes, and 2 conserved open reading frames (orfs). Phylogenetic analysis using concatenated PCGs revealed that R. setigera and Melosira undulate, which also belongs to the class Coscinodiscophyceae, clustered together as expected. However, comparison of these two mtDNAs revealed extensive genome rearrangement events, suggesting large evolutionary distance. The complete mtDNA of R. setigera will facilitate research on the phylogenetic relationship among Rhizosolenia species, which will in turn facilitate exploration of the evolutionary relationships in the class of Coscinodiscophyceae.
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Affiliation(s)
- Yanxin Yao
- CAS Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China.,Laboratory of Marine Ecology and Environmental Science, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China.,School of Earth and Planetary, University of Chinese Academy of Sciences, Beijing, China.,Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao, China
| | - Feng Liu
- CAS Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China.,Laboratory of Marine Ecology and Environmental Science, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China.,Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao, China
| | - Nansheng Chen
- CAS Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China.,Laboratory of Marine Ecology and Environmental Science, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China.,Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao, China.,Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, Canada
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8
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Draft Whole-Genome Sequence of Triparma laevis f. inornata (Parmales, Bolidophyceae), Isolated from the Oyashio Region, Western North Pacific Ocean. Microbiol Resour Announc 2020; 9:9/33/e00367-20. [PMID: 32817146 PMCID: PMC7427184 DOI: 10.1128/mra.00367-20] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We present the first draft whole-genome sequence for the Parmales (Bolidophyceae, Heterokonta), a picoplanktonic sister group of diatoms, using a Triparma laevis f. inornata strain that was isolated from the Oyashio region in the western North Pacific Ocean. We present the first draft whole-genome sequence for the Parmales (Bolidophyceae, Heterokonta), a picoplanktonic sister group of diatoms, using a Triparma laevis f. inornata strain that was isolated from the Oyashio region in the western North Pacific Ocean.
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9
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Li Q, Ren Y, Xiang D, Shi X, Zhao J, Peng L, Zhao G. Comparative mitogenome analysis of two ectomycorrhizal fungi ( Paxillus) reveals gene rearrangement, intron dynamics, and phylogeny of basidiomycetes. IMA Fungus 2020; 11:12. [PMID: 32670777 PMCID: PMC7333402 DOI: 10.1186/s43008-020-00038-8] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2019] [Accepted: 06/23/2020] [Indexed: 02/07/2023] Open
Abstract
In this study, the mitogenomes of two Paxillus species were assembled, annotated and compared. The two mitogenomes of Paxillus involutus and P. rubicundulus comprised circular DNA molecules, with the size of 39,109 bp and 41,061 bp, respectively. Evolutionary analysis revealed that the nad4L gene had undergone strong positive selection in the two Paxillus species. In addition, 10.64 and 36.50% of the repetitive sequences were detected in the mitogenomes of P. involutus and P. rubicundulus, respectively, which might transfer between mitochondrial and nuclear genomes. Large-scale gene rearrangements and frequent intron gain/loss events were detected in 61 basidiomycete species, which revealed large variations in mitochondrial organization and size in Basidiomycota. In addition, the insertion sites of the basidiomycete introns were found to have a base preference. Phylogenetic analysis of the combined mitochondrial gene set gave identical and well-supported tree topologies, indicating that mitochondrial genes were reliable molecular markers for analyzing the phylogenetic relationships of Basidiomycota. This study is the first report on the mitogenomes of Paxillus, which will promote a better understanding of their contrasted ecological strategies, molecular evolution and phylogeny of these important ectomycorrhizal fungi and related basidiomycete species.
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Affiliation(s)
- Qiang Li
- Key Laboratory of Coarse Cereal Processing, Ministry of Agriculture and Rural Affairs, College of Pharmacy and Biological Engineering, Chengdu University, Chengdu, 610106 Sichuan China
| | - Yuanhang Ren
- Key Laboratory of Coarse Cereal Processing, Ministry of Agriculture and Rural Affairs, College of Pharmacy and Biological Engineering, Chengdu University, Chengdu, 610106 Sichuan China
| | - Dabing Xiang
- Key Laboratory of Coarse Cereal Processing, Ministry of Agriculture and Rural Affairs, College of Pharmacy and Biological Engineering, Chengdu University, Chengdu, 610106 Sichuan China
| | - Xiaodong Shi
- Key Laboratory of Coarse Cereal Processing, Ministry of Agriculture and Rural Affairs, College of Pharmacy and Biological Engineering, Chengdu University, Chengdu, 610106 Sichuan China
| | - Jianglin Zhao
- Key Laboratory of Coarse Cereal Processing, Ministry of Agriculture and Rural Affairs, College of Pharmacy and Biological Engineering, Chengdu University, Chengdu, 610106 Sichuan China
| | - Lianxin Peng
- Key Laboratory of Coarse Cereal Processing, Ministry of Agriculture and Rural Affairs, College of Pharmacy and Biological Engineering, Chengdu University, Chengdu, 610106 Sichuan China
- Present address: Key Laboratory of Coarse Cereal Processing, Ministry of Agriculture and Rural Affairs, 2025 # Chengluo Avenue, Chengdu, 610106 Sichuan China
| | - Gang Zhao
- Key Laboratory of Coarse Cereal Processing, Ministry of Agriculture and Rural Affairs, College of Pharmacy and Biological Engineering, Chengdu University, Chengdu, 610106 Sichuan China
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10
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Sato N. Complex origins of chloroplast membranes with photosynthetic machineries: multiple transfers of genes from divergent organisms at different times or a single endosymbiotic event? JOURNAL OF PLANT RESEARCH 2020; 133:15-33. [PMID: 31811433 PMCID: PMC6946739 DOI: 10.1007/s10265-019-01157-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2019] [Accepted: 12/01/2019] [Indexed: 05/10/2023]
Abstract
The paradigm "cyanobacterial origin of chloroplasts" is currently viewed as an established fact. However, we may have to re-consider the origin of chloroplast membranes, because membranes are not replicated by their own. It is the genes for lipid biosynthetic enzymes that are inherited. In the current understandings, these enzymes became encoded by the nuclear genome as a result of endosymbiotic gene transfer from the endosymbiont. However, we previously showed that many enzymes involved in the synthesis of chloroplast peptidoglycan and glycolipids did not originate from cyanobacteria. Here I present results of comprehensive phylogenetic analysis of chloroplast enzymes involved in fatty acid and lipid biosynthesis, as well as additional chloroplast components related to photosynthesis and gene expression. Four types of phylogenetic relationship between chloroplast enzymes (encoded by the chloroplast and nuclear genomes) and cyanobacterial counterparts were found: type 1, chloroplast enzymes diverged from inside of cyanobacterial clade; type 2, chloroplast and cyanobacterial enzymes are sister groups; type 3, chloroplast enzymes originated from homologs of bacteria other than cyanobacteria; type 4, chloroplast enzymes diverged from eukaryotic homologs. Estimation of evolutionary distances suggested that the acquisition times of chloroplast enzymes were diverse, indicating that multiple gene transfers accounted for the chloroplast enzymes analyzed. Based on the results, I try to relax the tight logic of the endosymbiotic origin of chloroplasts involving a single endosymbiotic event by proposing alternative hypotheses. The hypothesis of host-directed chloroplast formation proposes that glycolipid synthesis ability had been acquired by the eukaryotic host before the acquisition of chloroplast ribosomes. Chloroplast membrane system could have been provided by the host, whereas cyanobacteria contributed to the genes for the genetic and photosynthesis systems, at various times, either before or after the formation of chloroplast membranes. The origin(s) of chloroplasts seems to be more complicated than the single event of primary endosymbiosis.
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Affiliation(s)
- Naoki Sato
- Department of Life Sciences, Graduate School of Arts and Sciences, University of Tokyo, Tokyo, 153-8902, Japan.
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11
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Han KY, Maciszewski K, Graf L, Yang JH, Andersen RA, Karnkowska A, Yoon HS. Dictyochophyceae Plastid Genomes Reveal Unusual Variability in Their Organization. JOURNAL OF PHYCOLOGY 2019; 55:1166-1180. [PMID: 31325913 DOI: 10.1111/jpy.12904] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2019] [Accepted: 07/01/2019] [Indexed: 05/22/2023]
Abstract
Dictyochophyceae (silicoflagellates) are unicellular freshwater and marine algae (Heterokontophyta, stramenopiles). Despite their abundance in global oceans and potential ecological significance, discovered in recent years, neither nuclear nor organellar genomes of representatives of this group were sequenced until now. Here, we present the first complete plastid genome sequences of Dictyochophyceae, obtained from four species: Dictyocha speculum, Rhizochromulina marina, Florenciella parvula and Pseudopedinella elastica. Despite their comparable size and genetic content, these four plastid genomes exhibit variability in their organization: plastid genomes of F. parvula and P. elastica possess conventional quadripartite structure with a pair of inverted repeats, R. marina instead possesses two direct repeats with the same orientation and D. speculum possesses no repeats at all. We also observed a number of unusual traits in the plastid genome of D. speculum, including expansion of the intergenic regions, presence of an intron in the otherwise non-intron-bearing psaA gene, and an additional copy of the large subunit of RuBisCO gene (rbcL), the last of which has never been observed in any plastid genome. We conclude that despite noticeable gene content similarities between the plastid genomes of Dictyochophyceae and their relatives (pelagophytes, diatoms), the number of distinctive features observed in this lineage strongly suggests that additional taxa require further investigation.
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Affiliation(s)
- Kwi Young Han
- Department of Biological Science, Sungkyunkwan University, Suwon, 16419, Korea
| | - Kacper Maciszewski
- Department of Molecular Phylogenetics and Evolution, Faculty of Biology, Biological and Chemical Research Centre, University of Warsaw, Żwirki i Wigury 101, 02-089, Warsaw, Poland
| | - Louis Graf
- Department of Biological Science, Sungkyunkwan University, Suwon, 16419, Korea
| | - Ji Hyun Yang
- Department of Biological Science, Sungkyunkwan University, Suwon, 16419, Korea
| | - Robert A Andersen
- Friday Harbor Laboratories, University of Washington, Friday Harbor, Washington, 98250, USA
| | - Anna Karnkowska
- Department of Molecular Phylogenetics and Evolution, Faculty of Biology, Biological and Chemical Research Centre, University of Warsaw, Żwirki i Wigury 101, 02-089, Warsaw, Poland
| | - Hwan Su Yoon
- Department of Biological Science, Sungkyunkwan University, Suwon, 16419, Korea
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12
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Ševcíková T, Yurchenko T, Fawley KP, Amaral R, Strnad H, Santos LMA, Fawley MW, Eliáš M. Plastid Genomes and Proteins Illuminate the Evolution of Eustigmatophyte Algae and Their Bacterial Endosymbionts. Genome Biol Evol 2019; 11:362-379. [PMID: 30629162 PMCID: PMC6367104 DOI: 10.1093/gbe/evz004] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/05/2019] [Indexed: 12/26/2022] Open
Abstract
Eustigmatophytes, a class of stramenopile algae (ochrophytes), include not only the extensively studied biotechnologically important genus Nannochloropsis but also a rapidly expanding diversity of lineages with much less well characterized biology. Recent discoveries have led to exciting additions to our knowledge about eustigmatophytes. Some proved to harbor bacterial endosymbionts representing a novel genus, Candidatus Phycorickettsia, and an operon of unclear function (ebo) obtained by horizontal gene transfer from the endosymbiont lineage was found in the plastid genomes of still other eustigmatophytes. To shed more light on the latter event, as well as to generally improve our understanding of the eustigmatophyte evolutionary history, we sequenced plastid genomes of seven phylogenetically diverse representatives (including new isolates representing undescribed taxa). A phylogenomic analysis of plastid genome-encoded proteins resolved the phylogenetic relationships among the main eustigmatophyte lineages and provided a framework for the interpretation of plastid gene gains and losses in the group. The ebo operon gain was inferred to have probably occurred within the order Eustigmatales, after the divergence of the two basalmost lineages (a newly discovered hitherto undescribed strain and the Pseudellipsoidion group). When looking for nuclear genes potentially compensating for plastid gene losses, we noticed a gene for a plastid-targeted acyl carrier protein that was apparently acquired by horizontal gene transfer from Phycorickettsia. The presence of this gene in all eustigmatophytes studied, including representatives of both principal clades (Eustigmatales and Goniochloridales), is a genetic footprint indicating that the eustigmatophyte-Phycorickettsia partnership started no later than in the last eustigmatophyte common ancestor.
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Affiliation(s)
- Tereza Ševcíková
- Department of Biology and Ecology Faculty of Science, University of Ostrava, Ostrava, Czech Republic
| | - Tatiana Yurchenko
- Faculty of Science, Institute of Environmental Technologies, University of Ostrava, Ostrava, Czech Republic
| | - Karen P Fawley
- Division of Sciences and Mathematics, University of the Ozarks, Clarksville, Arkansas
| | - Raquel Amaral
- Coimbra Collection of Algae (ACOI), Department of Life Sciences, University of Coimbra, Coimbra, Portugal
| | - Hynek Strnad
- Laboratory of Genomics and Bioinformatics, Institute of Molecular Genetics of the CAS, v.v.i., Prague, Czech Republic
| | - Lilia M A Santos
- Coimbra Collection of Algae (ACOI), Department of Life Sciences, University of Coimbra, Coimbra, Portugal
| | - Marvin W Fawley
- Division of Sciences and Mathematics, University of the Ozarks, Clarksville, Arkansas.,School of Mathematical and Natural Sciences, University of Arkansas at Monticello, Monticello, Arkansas
| | - Marek Eliáš
- Department of Biology and Ecology Faculty of Science, University of Ostrava, Ostrava, Czech Republic.,Faculty of Science, Institute of Environmental Technologies, University of Ostrava, Ostrava, Czech Republic
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13
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Yamada K, Katsura H, Noël MH, Ichinomiya M, Kuwata A, Sato S, Yoshikawa S. Ontogenetic analysis of siliceous cell wall formation in Triparma laevis f. inornata (Parmales, Stramenopiles). JOURNAL OF PHYCOLOGY 2019; 55:196-203. [PMID: 30320892 DOI: 10.1111/jpy.12800] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2018] [Accepted: 10/07/2018] [Indexed: 06/08/2023]
Abstract
Triparma laevis f. inornata is a unicellular alga belonging to the Bolidophyceae, which is most closely related to diatoms. Like diatoms, T. laevis f. inornata has a siliceous cell wall. The cell wall of T. laevis f. inornata consists of four round plates (three shields and one ventral plate) and one dorsal and three girdle plates. But, unlike diatoms, T. laevis f. inornata cells can grow when concentrations of silica are depleted. We took advantage of this ability, using TEM to study the ontogeny of the siliceous plate, pattern center formation, and development. Two types of pattern centers (annulus and sternum) were observed in the early and middle stage of plate formation. During their formation, the annuli were initially crescent-shaped but eventually their ends fused to make a ring. Only outward silica deposition of the branching ribs occurred on the growing annulus until it became a ring, resulting in an unfilled circle inside the annulus. The pattern center of the shield plate was always an annulus, but in ventral plates both annulus and sternum were observed. The annuli and sterna in T. laevis f. inornata round plates were very similar to the annuli and sterna in diatom valves. These results suggested that the round plates of Parmales are homologous to diatom valves. This information on the plate ontogeny of T. laevis f. inornata provides new insights into the evolution of the siliceous cell wall in the Parmales and diatoms.
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Affiliation(s)
- Kazumasa Yamada
- Faculty of Environmental & Symbiotic Sciences, Prefectural University of Kumamoto, 3-1-100 Tsukide, Kumamoto, 862-8502, Japan
| | - Hirotaka Katsura
- Department of Marine Science and Technology, Fukui Prefectural University, 1-1 Gakuen-cho, Obama, Fukui, 917-0003, Japan
| | - Mary-Hélène Noël
- National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, 305-8506, Japan
| | - Mutsuo Ichinomiya
- Faculty of Environmental & Symbiotic Sciences, Prefectural University of Kumamoto, 3-1-100 Tsukide, Kumamoto, 862-8502, Japan
| | - Akira Kuwata
- Tohoku National Fisheries Research Institute, 3-27-5 Shinhama-cho, Shiogama, Miyagi, 985-0001, Japan
| | - Shinya Sato
- Department of Marine Science and Technology, Fukui Prefectural University, 1-1 Gakuen-cho, Obama, Fukui, 917-0003, Japan
| | - Shinya Yoshikawa
- Department of Marine Science and Technology, Fukui Prefectural University, 1-1 Gakuen-cho, Obama, Fukui, 917-0003, Japan
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14
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Kim JI, Shin H, Škaloud P, Jung J, Yoon HS, Archibald JM, Shin W. Comparative plastid genomics of Synurophyceae: inverted repeat dynamics and gene content variation. BMC Evol Biol 2019; 19:20. [PMID: 30634905 PMCID: PMC6330437 DOI: 10.1186/s12862-018-1316-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2018] [Accepted: 12/04/2018] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The Synurophyceae is one of most important photosynthetic stramenopile algal lineages in freshwater ecosystems. They are characterized by siliceous scales covering the cell or colony surface and possess plastids of red-algal secondary or tertiary endosymbiotic origin. Despite their ecological and evolutionary significance, the relationships amongst extant Synurophyceae are unclear, as is their relationship to most other stramenopiles. RESULTS Here we report a comparative analysis of plastid genomes sequenced from five representative synurophycean algae. Most of these plastid genomes are highly conserved with respect to genome structure and coding capacity, with the exception of gene re-arrangements and partial duplications at the boundary of the inverted repeat and single-copy regions. Several lineage-specific gene loss/gain events and intron insertions were detected (e.g., cemA, dnaB, syfB, and trnL). CONCLUSIONS Unexpectedly, the cemA gene of Synurophyceae shows a strong relationship with sequences from members of the green-algal lineage, suggesting the occurrence of a lateral gene transfer event. Using a molecular clock approach based on silica fossil record data, we infer the timing of genome re-arrangement and gene gain/loss events in the plastid genomes of Synurophyceae.
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Affiliation(s)
- Jong Im Kim
- Department of Biology, Chungnam National University, Daejeon, 34134, South Korea
| | - Hyunmoon Shin
- Department of Biology, Chungnam National University, Daejeon, 34134, South Korea
| | - Pavel Škaloud
- Department of Botany, Faculty of Science, Charles University, Benátská 2, CZ-12800, Prague 2, Czech Republic
| | - Jaehee Jung
- Department of General Education, Hongik University, Seoul, 04066, South Korea
| | - Hwan Su Yoon
- Department of Biological Sciences, Sungkyunkwan University, Suwon, 16419, South Korea
| | - John M Archibald
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova Scotia, B3H 4R2, Canada.
| | - Woongghi Shin
- Department of Biology, Chungnam National University, Daejeon, 34134, South Korea.
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15
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Liu F, Jin Z, Wang Y, Bi Y, Melton JT. Plastid Genome of Dictyopteris divaricata (Dictyotales, Phaeophyceae): Understanding the Evolution of Plastid Genomes in Brown Algae. MARINE BIOTECHNOLOGY (NEW YORK, N.Y.) 2017; 19:627-637. [PMID: 29164355 DOI: 10.1007/s10126-017-9781-5] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2017] [Accepted: 11/05/2017] [Indexed: 06/07/2023]
Abstract
Dictyotophycidae is a subclass of brown algae containing 395 species that are distributed worldwide. A complete plastid (chloroplast) genome (ptDNA or cpDNA) had not previously been sequenced from this group. In this study, the complete plastid genome of Dictyopteris divaricata (Okamura) Okamura (Dictyotales, Phaeophyceae) was characterized and compared to other brown algal ptDNAs. This plastid genome was 126,099 bp in size with two inverted repeats (IRs) of 6026 bp. The D. divaricata IRs contained rpl21, making its IRs larger than representatives from the orders Fucales and Laminariales, but was smaller than that from Ectocarpales. The G + C content of D. divaricata (31.19%) was the highest of the known ptDNAs of brown algae (28.94-31.05%). Two protein-coding genes, rbcR and rpl32, were present in ptDNAs of Laminariales, Ectocarpales (Ectocarpus siliculosus), and Fucales (LEF) but were absent in D. divaricata. Reduced intergenic space (13.11%) and eight pairs of overlapping genes in D. divaricata ptDNA made it the most compact plastid genome in brown algae so far. The architecture of D. divaricata ptDNA showed higher similarity to that of Laminariales compared with Fucales and Ectocarpales. The difference in general features, gene content, and architecture among the ptDNAs of D. divaricata and LEF clade revealed the diversity and evolutionary trends of plastid genomes in brown algae.
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Affiliation(s)
- Feng Liu
- Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, Shandong, 266071, People's Republic of China.
- Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, Shandong, 266237, People's Republic of China.
| | - Zhe Jin
- Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, Shandong, 266071, People's Republic of China
- College of Life Science, Shandong Normal University, Jinan, Shandong, 250014, People's Republic of China
| | - Yu Wang
- Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, Shandong, 266071, People's Republic of China
- School of Life Sciences, Shandong University, Jinan, Shandong, 250100, People's Republic of China
| | - Yuping Bi
- Biotechnology Research Center, Shandong Academy of Agricultural Sciences, Jinan, Shandong, 250100, People's Republic of China
| | - James T Melton
- Department of Biological Sciences, The University of Alabama, Tuscaloosa, AL, 35487-0345, USA
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16
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Yurchenko T, Ševčíková T, Strnad H, Butenko A, Eliáš M. The plastid genome of some eustigmatophyte algae harbours a bacteria-derived six-gene cluster for biosynthesis of a novel secondary metabolite. Open Biol 2017; 6:rsob.160249. [PMID: 27906133 PMCID: PMC5133447 DOI: 10.1098/rsob.160249] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2016] [Accepted: 10/31/2016] [Indexed: 01/26/2023] Open
Abstract
Acquisition of genes by plastid genomes (plastomes) via horizontal gene transfer (HGT) seems to be a rare phenomenon. Here, we report an interesting case of HGT revealed by sequencing the plastomes of the eustigmatophyte algae Monodopsis sp. MarTras21 and Vischeria sp. CAUP Q 202. These plastomes proved to harbour a unique cluster of six genes, most probably acquired from a bacterium of the phylum Bacteroidetes, with homologues in various bacteria, typically organized in a conserved uncharacterized putative operon. Sequence analyses of the six proteins encoded by the operon yielded the following annotation for them: (i) a novel family without discernible homologues; (ii) a new family within the superfamily of metallo-dependent hydrolases; (iii) a novel subgroup of the UbiA superfamily of prenyl transferases; (iv) a new clade within the sugar phosphate cyclase superfamily; (v) a new family within the xylose isomerase-like superfamily; and (vi) a hydrolase for a phosphate moiety-containing substrate. We suggest that the operon encodes enzymes of a pathway synthesizing an isoprenoid–cyclitol-derived compound, possibly an antimicrobial or other protective substance. To the best of our knowledge, this is the first report of an expansion of the metabolic capacity of a plastid mediated by HGT into the plastid genome.
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Affiliation(s)
- Tatiana Yurchenko
- Faculty of Science, Department of Biology and Ecology, Life Science Research Centre, University of Ostrava, Chittussiho 10, 710 00 Ostrava, Czech Republic.,Faculty of Science, Institute of Environmental Technologies, University of Ostrava, Chittussiho 10, 710 00 Ostrava, Czech Republic
| | - Tereza Ševčíková
- Faculty of Science, Department of Biology and Ecology, Life Science Research Centre, University of Ostrava, Chittussiho 10, 710 00 Ostrava, Czech Republic
| | - Hynek Strnad
- Institute of Molecular Genetics of the ASCR, v. v. i., Prague, Czech Republic
| | - Anzhelika Butenko
- Faculty of Science, Department of Biology and Ecology, Life Science Research Centre, University of Ostrava, Chittussiho 10, 710 00 Ostrava, Czech Republic
| | - Marek Eliáš
- Faculty of Science, Department of Biology and Ecology, Life Science Research Centre, University of Ostrava, Chittussiho 10, 710 00 Ostrava, Czech Republic .,Faculty of Science, Institute of Environmental Technologies, University of Ostrava, Chittussiho 10, 710 00 Ostrava, Czech Republic
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17
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Ruck EC, Linard SR, Nakov T, Theriot EC, Alverson AJ. Hoarding and horizontal transfer led to an expanded gene and intron repertoire in the plastid genome of the diatom, Toxarium undulatum (Bacillariophyta). Curr Genet 2016; 63:499-507. [PMID: 27655214 DOI: 10.1007/s00294-016-0652-9] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2016] [Revised: 09/12/2016] [Accepted: 09/16/2016] [Indexed: 11/25/2022]
Abstract
Although the plastid genomes of diatoms maintain a conserved architecture and core gene set, considerable variation about this core theme exists and can be traced to several different processes. Gene duplication, pseudogenization, and loss, as well as intracellular transfer of genes to the nuclear genome, have all contributed to variation in gene content among diatom species. In addition, some noncoding sequences have highly restricted phylogenetic distributions that suggest a recent foreign origin. We sequenced the plastid genome of the marine diatom, Toxarium undulatum, and found that the genome contains three genes (chlB, chlL, and chlN) involved in light-independent chlorophyll a biosynthesis that were not previously known from diatoms. Phylogenetic and syntenic data suggest that these genes were differentially retained in this one lineage as they were repeatedly lost from most other diatoms. Unique among diatoms and other heterokont algae sequenced so far, the genome also contains a large group II intron within an otherwise intact psaA gene. Although the intron is most similar to one in the plastid-encoded psaA gene of some green algae, high sequence divergence between the diatom and green algal introns rules out recent shared ancestry. We conclude that the psaA intron was likely introduced into the plastid genome of T. undulatum, or some earlier ancestor, by horizontal transfer from an unknown donor. This genome further highlights the myriad processes driving variation in gene and intron content in the plastid genomes of diatoms, one of the world's foremost primary producers.
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Affiliation(s)
- Elizabeth C Ruck
- Department of Biological Sciences, University of Arkansas, Fayetteville, AR, USA
| | - Samantha R Linard
- Department of Biological Sciences, University of Arkansas, Fayetteville, AR, USA
| | - Teofil Nakov
- Department of Biological Sciences, University of Arkansas, Fayetteville, AR, USA
| | - Edward C Theriot
- Section of Integrative Biology, University of Texas at Austin, Austin, TX, 78712, USA
| | - Andrew J Alverson
- Department of Biological Sciences, University of Arkansas, Fayetteville, AR, USA.
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