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Laetz EMJ, Kahyaoglu C, Borgstein NM, Merkx M, van der Meij SET, Verberk WCEP. Critical thermal maxima and oxygen uptake in Elysia viridis, a sea slug that steals chloroplasts to photosynthesize. J Exp Biol 2024; 227:jeb246331. [PMID: 38629207 DOI: 10.1242/jeb.246331] [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: 06/19/2023] [Accepted: 03/31/2024] [Indexed: 05/31/2024]
Abstract
Photosynthetic animals produce oxygen, providing an ideal lens for studying how oxygen dynamics influence thermal sensitivity. The algivorous sea slug Elysia viridis can steal and retain chloroplasts from the marine alga Bryopsis sp. for months when starved, but chloroplast retention is mere weeks when they are fed another green alga, Chaetomorpha sp. To examine plasticity in thermal tolerance and changes in net oxygen exchange when fed and starving, slugs fed each alga were acclimated to 17°C (the current maximum temperature to which they are exposed in nature) and 22°C (the increase predicted for 2100) and measured at different points during starvation. We also examined increased illumination to evaluate a potential tradeoff between increased oxygen production but faster chloroplast degradation. Following acclimation, we subjected slugs to acute thermal stress to determine their thermal tolerance. We also measured net oxygen exchange before and after acute thermal stress. Thermal tolerance improved in slugs acclimated to 22°C, indicating they can acclimate to temperatures higher than they naturally experience. All slugs exhibited net oxygen uptake, and rates were highest in recently fed slugs before exposure to acute thermal stress. Oxygen uptake was suppressed following acute thermal stress. Under brighter light, slugs exhibited improved thermal tolerance, possibly because photosynthetic oxygen production alleviated oxygen limitation. Accordingly, this advantage disappeared later in starvation when photosynthesis ceased. Thus, E. viridis can cope with heatwaves by suppressing metabolism and plastically adjusting heat tolerance; however, starvation influences a slug's thermal tolerance and oxygen uptake such that continuous access to algal food for its potential nutritive and oxygenic benefits is critical when facing thermal stress.
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Affiliation(s)
- Elise M J Laetz
- Groningen Institute for Evolutionary Life Sciences, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| | - Can Kahyaoglu
- Groningen Institute for Evolutionary Life Sciences, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| | - Natascha M Borgstein
- Groningen Institute for Evolutionary Life Sciences, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| | - Michiel Merkx
- Groningen Institute for Evolutionary Life Sciences, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| | - Sancia E T van der Meij
- Groningen Institute for Evolutionary Life Sciences, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
- Naturalis Biodiversity Center, Darwinweg 2, 2333 CR Leiden, The Netherlands
| | - Wilco C E P Verberk
- Department of Ecology, Radboud University Nijmegen, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
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Morelli L, Cartaxana P, Cruz S. Food shaped photosynthesis: Photophysiology of the sea slug Elysia viridis fed with two alternative chloroplast donors. OPEN RESEARCH EUROPE 2024; 3:107. [PMID: 38725452 PMCID: PMC11079582 DOI: 10.12688/openreseurope.16162.2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Accepted: 02/26/2024] [Indexed: 05/12/2024]
Abstract
Background Some Sacoglossa sea slugs steal and integrate chloroplasts derived from the algae they feed on into their cells where they continue to function photosynthetically, a process termed kleptoplasty. The stolen chloroplasts - kleptoplasts - can maintain their functionality up to several months and support animal metabolism. However, chloroplast longevity can vary depending on sea slug species and algal donor. In this study, we focused on Elysia viridis, a polyphagous species that is mostly found associated with the macroalga Codium tomentosum, but that was reported to eat other macroalgae, including Chaetomorpha sp. Methods We have investigated the changes in E. viridis physiology when provided with the two different food sources to evaluate to which extent the photosynthetic and photoprotective mechanisms of the algae chloroplasts matched those of the plastids once in the animal cells. To perform the study, we rely on the evaluation of chlorophyll a variable fluorescence to study the photophysiological state of the integrated kleptoplasts and high-performance liquid chromatography (HPLC) to study variations in the photosynthetic pigments. Results We observed that the photosynthetic efficiency of E. viridis is lower when fed with Chaetomorpha. Also, significant differences were observed in the non-photochemical quenching (NPQ) abilities of the sea slugs. While sea slugs fed with C. tomentosum react similarly to high-light stress as the alga, E. viridis hosting Chaetomorpha chloroplasts were unable to properly recover from photoinhibition or perform a functional xanthophyll cycle (XC). Conclusions Our results showed that, even if the sea slugs fed with the two algae show photosynthetic activities like the respective algal donors, not all the photoprotective mechanisms present in Chaetomorpha can be maintained in E. viridis. This indicates that the functionality of the kleptoplasts does not depend solely on their origin but also on the degree of compatibility with the animal species integrating them.
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Affiliation(s)
- Luca Morelli
- CESAM – Centre for Environmental and Marine Studies, Department of Biology, University of Aveiro, Aveiro, Aveiro District, 3810-193, Portugal
| | - Paulo Cartaxana
- CESAM – Centre for Environmental and Marine Studies, Department of Biology, University of Aveiro, Aveiro, Aveiro District, 3810-193, Portugal
| | - Sónia Cruz
- CESAM – Centre for Environmental and Marine Studies, Department of Biology, University of Aveiro, Aveiro, Aveiro District, 3810-193, Portugal
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3
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Li F, Lin Z, Krug PJ, Catrow JL, Cox JE, Schmidt EW. Animal FAS-like polyketide synthases produce diverse polypropionates. Proc Natl Acad Sci U S A 2023; 120:e2305575120. [PMID: 37695909 PMCID: PMC10515154 DOI: 10.1073/pnas.2305575120] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Accepted: 08/01/2023] [Indexed: 09/13/2023] Open
Abstract
Animal cytoplasmic fatty acid synthase (FAS) represents a unique family of enzymes that are classically thought to be most closely related to fungal polyketide synthase (PKS). Recently, a widespread family of animal lipid metabolic enzymes has been described that bridges the gap between these two ubiquitous and important enzyme classes: the animal FAS-like PKSs (AFPKs). Although very similar in sequence to FAS enzymes that produce saturated lipids widely found in animals, AFPKs instead produce structurally diverse compounds that resemble bioactive polyketides. Little is known about the factors that bridge lipid and polyketide synthesis in the animals. Here, we describe the function of EcPKS2 from Elysia chlorotica, which synthesizes a complex polypropionate natural product found in this mollusc. EcPKS2 starter unit promiscuity potentially explains the high diversity of polyketides found in and among molluscan species. Biochemical comparison of EcPKS2 with the previously described EcPKS1 reveals molecular principles governing substrate selectivity that should apply to related enzymes encoded within the genomes of photosynthetic gastropods. Hybridization experiments combining EcPKS1 and EcPKS2 demonstrate the interactions between the ketoreductase and ketosynthase domains in governing the product outcomes. Overall, these findings enable an understanding of the molecular principles of structural diversity underlying the many molluscan polyketides likely produced by the diverse AFPK enzyme family.
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Affiliation(s)
- Feng Li
- Department of Medicinal Chemistry, University of Utah, Salt Lake City, UT84112
| | - Zhenjian Lin
- Department of Medicinal Chemistry, University of Utah, Salt Lake City, UT84112
| | - Patrick J. Krug
- Department of Biological Sciences, California State University, Los Angeles, CA90032
| | - J. Leon Catrow
- Metabolomics Core, Health Sciences Center, Salt Lake City, UT84112
| | - James E. Cox
- Metabolomics Core, Health Sciences Center, Salt Lake City, UT84112
- Department of Biochemistry, University of Utah, Salt Lake City, UT84112
| | - Eric W. Schmidt
- Department of Medicinal Chemistry, University of Utah, Salt Lake City, UT84112
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Cartaxana P, Morelli L, Cassin E, Havurinne V, Cabral M, Cruz S. Prey species and abundance affect growth and photosynthetic performance of the polyphagous sea slug Elysia crispata. ROYAL SOCIETY OPEN SCIENCE 2023; 10:230810. [PMID: 37650060 PMCID: PMC10465201 DOI: 10.1098/rsos.230810] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2023] [Accepted: 08/10/2023] [Indexed: 09/01/2023]
Abstract
Some sacoglossan sea slugs steal functional macroalgal chloroplasts (kleptoplasts). In this study, we investigated the effects of algal prey species and abundance on the growth and photosynthetic capacity of the tropical polyphagous sea slug Elysia crispata. Recently hatched sea slugs fed and acquired chloroplasts from the macroalga Bryopsis plumosa, but not from Acetabularia acetabulum. However, adult sea slugs were able to switch diet to A. acetabulum, rapidly replacing the great majority of the original kleptoplasts. When fed with B. plumosa, higher feeding frequency resulted in significantly higher growth and kleptoplast photosynthetic yield, as well as a slower relative decrease in these parameters upon starvation. Longevity of A. acetabulum-derived chloroplasts in E. crispata was over twofold that of B. plumosa. Furthermore, significantly lower relative weight loss under starvation was observed in sea slugs previously fed on A. acetabulum than on B. plumosa. This study shows that functionality and longevity of kleptoplasts in photosynthetic sea slugs depend on the origin of the plastids. Furthermore, we have identified A. acetabulum as a donor of photosynthetically efficient chloroplasts common to highly specialized monophagous and polyphagous sea slugs capable of long-term retention, which opens new experimental routes to unravel the unsolved mysteries of kleptoplasty.
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Affiliation(s)
- Paulo Cartaxana
- ECOMARE – Laboratory for Innovation and Sustainability of Marine Biological Resources, CESAM – Centre for Environmental and Marine Studies, Department of Biology, University of Aveiro, Aveiro 3810-193, Portugal
| | - Luca Morelli
- ECOMARE – Laboratory for Innovation and Sustainability of Marine Biological Resources, CESAM – Centre for Environmental and Marine Studies, Department of Biology, University of Aveiro, Aveiro 3810-193, Portugal
| | - Elena Cassin
- ECOMARE – Laboratory for Innovation and Sustainability of Marine Biological Resources, CESAM – Centre for Environmental and Marine Studies, Department of Biology, University of Aveiro, Aveiro 3810-193, Portugal
| | - Vesa Havurinne
- ECOMARE – Laboratory for Innovation and Sustainability of Marine Biological Resources, CESAM – Centre for Environmental and Marine Studies, Department of Biology, University of Aveiro, Aveiro 3810-193, Portugal
| | - Miguel Cabral
- ECOMARE – Laboratory for Innovation and Sustainability of Marine Biological Resources, CESAM – Centre for Environmental and Marine Studies, Department of Biology, University of Aveiro, Aveiro 3810-193, Portugal
| | - Sónia Cruz
- ECOMARE – Laboratory for Innovation and Sustainability of Marine Biological Resources, CESAM – Centre for Environmental and Marine Studies, Department of Biology, University of Aveiro, Aveiro 3810-193, Portugal
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5
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Abstract
Kleptoplasty, the process by which a host organism sequesters and retains algal chloroplasts, is relatively common in protists. The origin of the plastid varies, as do the length of time it is retained in the host and the functionality of the association. In metazoa, the capacity for long-term (several weeks to months) maintenance of photosynthetically active chloroplasts is a unique characteristic of a handful of sacoglossan sea slugs. This capability has earned these slugs the epithets "crawling leaves" and "solar-powered sea slugs." This Unsolved Mystery explores the basis of chloroplast maintenance and function and attempts to clarify contradictory results in the published literature. We address some of the mysteries of this remarkable association. Why are functional chloroplasts retained? And how is the function of stolen chloroplasts maintained without the support of the algal nucleus?
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6
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Phylogeny and evolution of functional chloroplast retention in sacoglossan sea slugs (Gastropoda: Heterobranchia). ORG DIVERS EVOL 2021. [DOI: 10.1007/s13127-021-00532-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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7
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Havurinne V, Handrich M, Antinluoma M, Khorobrykh S, Gould SB, Tyystjärvi E. Genetic autonomy and low singlet oxygen yield support kleptoplast functionality in photosynthetic sea slugs. JOURNAL OF EXPERIMENTAL BOTANY 2021; 72:5553-5568. [PMID: 33989402 PMCID: PMC8318255 DOI: 10.1093/jxb/erab216] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Accepted: 05/12/2021] [Indexed: 05/04/2023]
Abstract
The kleptoplastic sea slug Elysia chlorotica consumes Vaucheria litorea, stealing its plastids, which then photosynthesize inside the animal cells for months. We investigated the properties of V. litorea plastids to understand how they withstand the rigors of photosynthesis in isolation. Transcription of specific genes in laboratory-isolated V. litorea plastids was monitored for 7 days. The involvement of plastid-encoded FtsH, a key plastid maintenance protease, in recovery from photoinhibition in V. litorea was estimated in cycloheximide-treated cells. In vitro comparison of V. litorea and spinach thylakoids was applied to investigate reactive oxygen species formation in V. litorea. In comparison to other tested genes, the transcripts of ftsH and translation elongation factor EF-Tu (tufA) decreased slowly in isolated V. litorea plastids. Higher levels of FtsH were also evident in cycloheximide-treated cells during recovery from photoinhibition. Charge recombination in PSII of V. litorea was found to be fine-tuned to produce only small quantities of singlet oxygen, and the plastids also contained reactive oxygen species-protective compounds. Our results support the view that the genetic characteristics of the plastids are crucial in creating a photosynthetic sea slug. The plastid's autonomous repair machinery is likely enhanced by low singlet oxygen production and elevated expression of FtsH.
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Affiliation(s)
- Vesa Havurinne
- Department of Biotechnology/Molecular Plant Biology, University of Turku, Turku, Finland
| | - Maria Handrich
- Department of Biology, Heinrich-Heine-Universität, Düsseldorf, Germany
| | - Mikko Antinluoma
- Department of Biotechnology/Molecular Plant Biology, University of Turku, Turku, Finland
| | - Sergey Khorobrykh
- Department of Biotechnology/Molecular Plant Biology, University of Turku, Turku, Finland
| | - Sven B Gould
- Department of Biology, Heinrich-Heine-Universität, Düsseldorf, Germany
| | - Esa Tyystjärvi
- Department of Biotechnology/Molecular Plant Biology, University of Turku, Turku, Finland
- Correspondence:
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8
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Havurinne V, Handrich M, Antinluoma M, Khorobrykh S, Gould SB, Tyystjärvi E. Genetic autonomy and low singlet oxygen yield support kleptoplast functionality in photosynthetic sea slugs. JOURNAL OF EXPERIMENTAL BOTANY 2021. [PMID: 33989402 DOI: 10.17632/535dcxjt2d.1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
The kleptoplastic sea slug Elysia chlorotica consumes Vaucheria litorea, stealing its plastids, which then photosynthesize inside the animal cells for months. We investigated the properties of V. litorea plastids to understand how they withstand the rigors of photosynthesis in isolation. Transcription of specific genes in laboratory-isolated V. litorea plastids was monitored for 7 days. The involvement of plastid-encoded FtsH, a key plastid maintenance protease, in recovery from photoinhibition in V. litorea was estimated in cycloheximide-treated cells. In vitro comparison of V. litorea and spinach thylakoids was applied to investigate reactive oxygen species formation in V. litorea. In comparison to other tested genes, the transcripts of ftsH and translation elongation factor EF-Tu (tufA) decreased slowly in isolated V. litorea plastids. Higher levels of FtsH were also evident in cycloheximide-treated cells during recovery from photoinhibition. Charge recombination in PSII of V. litorea was found to be fine-tuned to produce only small quantities of singlet oxygen, and the plastids also contained reactive oxygen species-protective compounds. Our results support the view that the genetic characteristics of the plastids are crucial in creating a photosynthetic sea slug. The plastid's autonomous repair machinery is likely enhanced by low singlet oxygen production and elevated expression of FtsH.
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Affiliation(s)
- Vesa Havurinne
- Department of Biotechnology/Molecular Plant Biology, University of Turku, Turku, Finland
| | - Maria Handrich
- Department of Biology, Heinrich-Heine-Universität, Düsseldorf, Germany
| | - Mikko Antinluoma
- Department of Biotechnology/Molecular Plant Biology, University of Turku, Turku, Finland
| | - Sergey Khorobrykh
- Department of Biotechnology/Molecular Plant Biology, University of Turku, Turku, Finland
| | - Sven B Gould
- Department of Biology, Heinrich-Heine-Universität, Düsseldorf, Germany
| | - Esa Tyystjärvi
- Department of Biotechnology/Molecular Plant Biology, University of Turku, Turku, Finland
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Maeda T, Takahashi S, Yoshida T, Shimamura S, Takaki Y, Nagai Y, Toyoda A, Suzuki Y, Arimoto A, Ishii H, Satoh N, Nishiyama T, Hasebe M, Maruyama T, Minagawa J, Obokata J, Shigenobu S. Chloroplast acquisition without the gene transfer in kleptoplastic sea slugs, Plakobranchus ocellatus. eLife 2021; 10:60176. [PMID: 33902812 PMCID: PMC8079154 DOI: 10.7554/elife.60176] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Accepted: 04/01/2021] [Indexed: 12/14/2022] Open
Abstract
Some sea slugs sequester chloroplasts from algal food in their intestinal cells and photosynthesize for months. This phenomenon, kleptoplasty, poses a question of how the chloroplast retains its activity without the algal nucleus. There have been debates on the horizontal transfer of algal genes to the animal nucleus. To settle the arguments, this study reported the genome of a kleptoplastic sea slug, Plakobranchus ocellatus, and found no evidence of photosynthetic genes encoded on the nucleus. Nevertheless, it was confirmed that light illumination prolongs the life of mollusk under starvation. These data presented a paradigm that a complex adaptive trait, as typified by photosynthesis, can be transferred between eukaryotic kingdoms by a unique organelle transmission without nuclear gene transfer. Our phylogenomic analysis showed that genes for proteolysis and immunity undergo gene expansion and are up-regulated in chloroplast-enriched tissue, suggesting that these molluskan genes are involved in the phenotype acquisition without horizontal gene transfer.
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Affiliation(s)
- Taro Maeda
- National Institute for Basic Biology, Okazaki, Japan
| | - Shunichi Takahashi
- Sesoko Station, Tropical Biosphere Research Center, University of the Ryukyu, Okinawa, Japan
| | - Takao Yoshida
- Japan Agency for Marine-Earth Science and Technology, Yokosuka, Japan
| | - Shigeru Shimamura
- Japan Agency for Marine-Earth Science and Technology, Yokosuka, Japan
| | - Yoshihiro Takaki
- Japan Agency for Marine-Earth Science and Technology, Yokosuka, Japan
| | - Yukiko Nagai
- Japan Agency for Marine-Earth Science and Technology, Yokosuka, Japan
| | | | | | - Asuka Arimoto
- Marine Biological Laboratory, Hiroshima University, Hiroshima, Japan
| | | | - Nori Satoh
- Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan
| | - Tomoaki Nishiyama
- Research Center for Experimental Modeling of Human Disease, Kanazawa University, Kanazawa, Japan
| | - Mitsuyasu Hasebe
- National Institute for Basic Biology, Okazaki, Japan.,SOKENDAI, the Graduate University for Advanced Studies, Okazaki, Japan
| | | | - Jun Minagawa
- National Institute for Basic Biology, Okazaki, Japan.,SOKENDAI, the Graduate University for Advanced Studies, Okazaki, Japan
| | - Junichi Obokata
- Kyoto Prefectural University, Kyoto, Japan.,Setsunan Universiy, Hirakata, Japan
| | - Shuji Shigenobu
- National Institute for Basic Biology, Okazaki, Japan.,SOKENDAI, the Graduate University for Advanced Studies, Okazaki, Japan
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10
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Melo Clavijo J, Frankenbach S, Fidalgo C, Serôdio J, Donath A, Preisfeld A, Christa G. Identification of scavenger receptors and thrombospondin-type-1 repeat proteins potentially relevant for plastid recognition in Sacoglossa. Ecol Evol 2020; 10:12348-12363. [PMID: 33209293 PMCID: PMC7663992 DOI: 10.1002/ece3.6865] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2020] [Revised: 08/20/2020] [Accepted: 08/27/2020] [Indexed: 12/24/2022] Open
Abstract
Functional kleptoplasty is a photosymbiotic relationship, in which photosynthetically active chloroplasts serve as an intracellular symbiont for a heterotrophic host. Among Metazoa, functional kleptoplasty is only found in marine sea slugs belonging to the Sacoglossa and recently described in Rhabdocoela worms. Although functional kleptoplasty has been intensively studied in Sacoglossa, the fundamentals of the specific recognition of the chloroplasts and their subsequent incorporation are unknown. The key to ensure the initiation of any symbiosis is the ability to specifically recognize the symbiont and to differentiate a symbiont from a pathogen. For instance, in photosymbiotic cnidarians, several studies have shown that the host innate immune system, in particular scavenger receptors (SRs) and thrombospondin-type-1 repeat (TSR) protein superfamily, is playing a major role in the process of recognizing and differentiating symbionts from pathogens. In the present study, SRs and TSRs of three Sacoglossa sea slugs, Elysia cornigera, Elysia timida, and Elysia chlorotica, were identified by translating available transcriptomes into potential proteins and searching for receptor specific protein and/or transmembrane domains. Both receptors classes are highly diverse in the slugs, and many new domain arrangements for each receptor class were found. The analyses of the gene expression of these three species provided a set of species-specific candidate genes, that is, SR-Bs, SR-Es, C-type lectins, and TSRs, that are potentially relevant for the recognition of kleptoplasts. The results set the base for future experimental studies to understand if and how these candidate receptors are indeed involved in chloroplast recognition.
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Affiliation(s)
- Jenny Melo Clavijo
- Fakultät für Mathematik und Naturwissenschaften, Zoologie und BiologiedidaktikBergische Universität WuppertalWuppertalGermany
| | - Silja Frankenbach
- Department of Biology and CESAM – Center for Environmental and Marine StudiesUniversity of AveiroAveiroPortugal
| | - Cátia Fidalgo
- Department of Biology and CESAM – Center for Environmental and Marine StudiesUniversity of AveiroAveiroPortugal
| | - João Serôdio
- Department of Biology and CESAM – Center for Environmental and Marine StudiesUniversity of AveiroAveiroPortugal
| | - Alexander Donath
- Center for Molecular Biodiversity ResearchZoological Research Museum Alexander KoenigBonnGermany
| | - Angelika Preisfeld
- Fakultät für Mathematik und Naturwissenschaften, Zoologie und BiologiedidaktikBergische Universität WuppertalWuppertalGermany
| | - Gregor Christa
- Fakultät für Mathematik und Naturwissenschaften, Zoologie und BiologiedidaktikBergische Universität WuppertalWuppertalGermany
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11
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Havurinne V, Tyystjärvi E. Photosynthetic sea slugs induce protective changes to the light reactions of the chloroplasts they steal from algae. eLife 2020; 9:57389. [PMID: 33077025 PMCID: PMC7679141 DOI: 10.7554/elife.57389] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2020] [Accepted: 10/07/2020] [Indexed: 12/13/2022] Open
Abstract
Sacoglossan sea slugs are able to maintain functional chloroplasts inside their own cells, and mechanisms that allow preservation of the chloroplasts are unknown. We found that the slug Elysia timida induces changes to the photosynthetic light reactions of the chloroplasts it steals from the alga Acetabularia acetabulum. Working with a large continuous laboratory culture of both the slugs (>500 individuals) and their prey algae, we show that the plastoquinone pool of slug chloroplasts remains oxidized, which can suppress reactive oxygen species formation. Slug chloroplasts also rapidly build up a strong proton-motive force upon a dark-to-light transition, which helps them to rapidly switch on photoprotective non-photochemical quenching of excitation energy. Finally, our results suggest that chloroplasts inside E. timida rely on oxygen-dependent electron sinks during rapid changes in light intensity. These photoprotective mechanisms are expected to contribute to the long-term functionality of the chloroplasts inside the slugs. Plants, algae and a few other organisms rely on a process known as photosynthesis to fuel themselves, as they can harness cellular structures called chloroplasts to convert light into usable energy. Animals typically lack chloroplasts, making them unable to use photosynthesis to power themselves. The sea slug Elysia timida, however, can steal whole chloroplasts from the cells of the algae it consumes: the stolen structures then become part of the cells in the gut of the slug, allowing the animal to gain energy from sunlight. Once they are in the digestive system of the slug, the chloroplasts survive and keep working for longer than expected. Indeed, these structures are often harmed as a side effect of photosynthesis, but the sea slug does not have the right genes to help repair this damage. In addition, conditions inside animal cells are widely different to the ones found inside algae and plants. It is not clear then how the sea slug extends the lifespan of its chloroplasts by preventing damage caused by sunlight. To investigate this question, Havurinne and Tyystjärvi compared photosynthesis in sea slugs and the algae they eat. A range of methods, including measuring fluorescence from the chloroplasts, was used: this revealed that the slug changes the inside of the stolen chloroplasts, making them more resistant to damage. First, when exposed to light the stolen chloroplasts can quickly switch on a mechanism that dissipates light energy to heat, which is less damaging. Second, a molecule that serves as an intermediate during photosynthesis is kept in a ‘safe’ state which prevents it from creating harmful compounds. And finally, additional safeguard molecules ‘deactivate’ compounds that could otherwise mediate damaging reactions. Overall, these measures may reduce the efficiency of the chloroplasts but allow them to keep working for much longer. Early chloroplasts were probably independent bacteria that were captured and ‘domesticated’ by other cells for their ability to extract energy from the sun. Photosynthesizing sea slugs therefore provide an interesting way to understand some of the challenges of early life. The work by Havurinne and Tyystjärvi may also reveal new ways to harness biological processes such as photosynthesis for energy production in other contexts.
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Affiliation(s)
- Vesa Havurinne
- University of Turku, Department of Biochemistry / Molecular Plant Biology, Turku, Finland
| | - Esa Tyystjärvi
- University of Turku, Department of Biochemistry / Molecular Plant Biology, Turku, Finland
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12
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Rey F, Melo T, Cartaxana P, Calado R, Domingues P, Cruz S, Domingues MRM. Coping with Starvation: Contrasting Lipidomic Dynamics in the Cells of Two Sacoglossan Sea Slugs Incorporating Stolen Plastids from the Same Macroalga. Integr Comp Biol 2020; 60:43-56. [PMID: 32294176 DOI: 10.1093/icb/icaa019] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Several species of sacoglossan sea slugs are able to sequester chloroplasts from algae and incorporate them into their cells. However, the ability to maintain functional "stolen" plastids (kleptoplasts) can vary significantly within the Sacoglossa, giving species different capacities to withstand periods of food shortage. The present study provides an insight on the comparative shifts experienced by the lipidome of two sacoglossan sea slug species, Elysia viridis (long-term retention of functional chloroplasts) and Placida dendritica (retention of non-functional chloroplasts). A hydrophilic interaction liquid chromatography-mass spectrometry approach was employed to screen the lipidome of specimens from both species feeding on the macroalga Codium tomentosum and after 1-week of starvation. The lipidome of E. viridis was generally unaffected by the absence of food, while that of P. dendritica varied significantly. The retention of functional chloroplasts by E. viridis cells allows this species to endure periods of food shortage, while in P. dendritica a significant reduction in the amount of main lipids was the consequence of the consumption of its own mass to endure starvation. The large proportion of ether phospholipids (plasmalogens) in both sea slug species suggests that these compounds may play a key role in chloroplast incorporation in sea slug cells and/or be involved in the reduction of the oxidative stress resulting from the presence of kleptoplasts.
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Affiliation(s)
- Felisa Rey
- CESAM, Department of Chemistry, University of Aveiro, Campus Universitário de Santiago, Aveiro 3810-193, Portugal.,Mass Spectrometry Centre & QOPNA & LAQV-REQUIMTE, Department of Chemistry, University of Aveiro, Campus Universitário de Santiago, Aveiro 3810-193, Portugal
| | - Tânia Melo
- CESAM, Department of Chemistry, University of Aveiro, Campus Universitário de Santiago, Aveiro 3810-193, Portugal.,Mass Spectrometry Centre & QOPNA & LAQV-REQUIMTE, Department of Chemistry, University of Aveiro, Campus Universitário de Santiago, Aveiro 3810-193, Portugal
| | - Paulo Cartaxana
- ECOMARE, CESAM, Department of Biology, University of Aveiro, Campus Universitário de Santiago, Aveiro 3810-193, Portugal
| | - Ricardo Calado
- ECOMARE, CESAM, Department of Biology, University of Aveiro, Campus Universitário de Santiago, Aveiro 3810-193, Portugal
| | - Pedro Domingues
- Mass Spectrometry Centre & QOPNA & LAQV-REQUIMTE, Department of Chemistry, University of Aveiro, Campus Universitário de Santiago, Aveiro 3810-193, Portugal
| | - Sónia Cruz
- ECOMARE, CESAM, Department of Biology, University of Aveiro, Campus Universitário de Santiago, Aveiro 3810-193, Portugal
| | - M Rosário M Domingues
- CESAM, Department of Chemistry, University of Aveiro, Campus Universitário de Santiago, Aveiro 3810-193, Portugal.,Mass Spectrometry Centre & QOPNA & LAQV-REQUIMTE, Department of Chemistry, University of Aveiro, Campus Universitário de Santiago, Aveiro 3810-193, Portugal
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13
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Torres JP, Lin Z, Winter JM, Krug PJ, Schmidt EW. Animal biosynthesis of complex polyketides in a photosynthetic partnership. Nat Commun 2020; 11:2882. [PMID: 32513940 PMCID: PMC7280274 DOI: 10.1038/s41467-020-16376-5] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2019] [Accepted: 04/29/2020] [Indexed: 11/09/2022] Open
Abstract
Complex polyketides are typically associated with microbial metabolism. Here, we report that animals also make complex, microbe-like polyketides. We show there is a widespread branch of fatty acid synthase- (FAS)-like polyketide synthase (PKS) proteins, which sacoglossan animals use to synthesize complex products. The purified sacogolassan protein EcPKS1 uses only methylmalonyl-CoA as a substrate, otherwise unknown in animal lipid metabolism. Sacoglossans are sea slugs, some of which eat algae, digesting the cells but maintaining functional chloroplasts. Here, we provide evidence that polyketides support this unusual photosynthetic partnership. The FAS-like PKS family represents an uncharacterized branch of polyketide and fatty acid metabolism, encoding a large diversity of biomedically relevant animal enzymes and chemicals awaiting discovery. The biochemical characterization of an intact animal polyketide biosynthetic enzyme opens the door to understanding the immense untapped metabolic potential of metazoans. Complex polyketides are usually produced by microbes, whereas the origin of polyketides found in animals remained unknown. This study shows that sacoglossan animals, such as sea slugs, employ fatty acid synthase-like proteins to produce microbe-like polyketides.
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Affiliation(s)
- Joshua P Torres
- Department of Medicinal Chemistry, University of Utah, Salt Lake City, UT, 84112, USA
| | - Zhenjian Lin
- Department of Medicinal Chemistry, University of Utah, Salt Lake City, UT, 84112, USA
| | - Jaclyn M Winter
- Department of Medicinal Chemistry, University of Utah, Salt Lake City, UT, 84112, USA
| | - Patrick J Krug
- Department of Biological Sciences, California State University, Los Angeles, CA, 90032, USA
| | - Eric W Schmidt
- Department of Medicinal Chemistry, University of Utah, Salt Lake City, UT, 84112, USA.
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14
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Donohoo SA, Wade RM, Sherwood AR. Finding the Sweet Spot: Sub-Ambient Light Increases Fitness and Kleptoplast Survival in the Sea Slug Plakobranchus cf. ianthobaptus Gould, 1852. THE BIOLOGICAL BULLETIN 2020; 238:154-166. [PMID: 32597715 DOI: 10.1086/709371] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Sacoglossans, or "sap-sucking" sea slugs, are primarily algivorous, with many taxa exhibiting kleptoplasty, the feeding and retaining of photosynthetically active chloroplasts from algae. The Plakobranchus species complex exhibits some of the longest kleptoplast retention and survival times under starvation conditions, but the contributions of these kleptoplasts to their survival and overall fitness have been widely debated. In this study we assessed the effects of starvation and light on the fitness of Plakobranchus cf. ianthobaptus and its kleptoplasts by placing starved individuals in eight daily average light treatments, ranging from near dark (2 µmol photon m-2 s-1) to ambient light (470 µmol photon m-2 s-1). Slug weight was used as a metric of fitness, and kleptoplast photosynthetic activity was determined via maximum quantum yield (Fv/Fm) by pulse-amplitude modulated fluorometry as a proxy for kleptoplast health. Plakobranchus individuals in near-dark and high light treatments (>160 µmol photon m-2 s-1) experienced significantly greater weight loss than those in low light (65 µmol photon m-2 s-1) and moderate light treatments (95-135 µmol photon m-2 s-1). Additionally, individuals in high light treatments experienced a rapid decline in kleptoplast photosynthetic activity, while all other treatments experienced minimal decline. This relationship between kleptoplast degradation and weight loss suggests an important link between fitness and kleptoplasty. Given the significant negative effects of ambient conditions, regular refreshment and replenishment of kleptoplasts or physiological or behavioral adjustments are likely employed for the benefits of kleptoplasty to be maintained.
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15
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Ganley JG, Derbyshire ER. Linking Genes to Molecules in Eukaryotic Sources: An Endeavor to Expand Our Biosynthetic Repertoire. Molecules 2020; 25:E625. [PMID: 32023950 PMCID: PMC7036892 DOI: 10.3390/molecules25030625] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2020] [Revised: 01/23/2020] [Accepted: 01/30/2020] [Indexed: 02/06/2023] Open
Abstract
The discovery of natural products continues to interest chemists and biologists for their utility in medicine as well as facilitating our understanding of signaling, pathogenesis, and evolution. Despite an attenuation in the discovery rate of new molecules, the current genomics and transcriptomics revolution has illuminated the untapped biosynthetic potential of many diverse organisms. Today, natural product discovery can be driven by biosynthetic gene cluster (BGC) analysis, which is capable of predicting enzymes that catalyze novel reactions and organisms that synthesize new chemical structures. This approach has been particularly effective in mining bacterial and fungal genomes where it has facilitated the discovery of new molecules, increased the understanding of metabolite assembly, and in some instances uncovered enzymes with intriguing synthetic utility. While relatively less is known about the biosynthetic potential of non-fungal eukaryotes, there is compelling evidence to suggest many encode biosynthetic enzymes that produce molecules with unique bioactivities. In this review, we highlight how the advances in genomics and transcriptomics have aided natural product discovery in sources from eukaryotic lineages. We summarize work that has successfully connected genes to previously identified molecules and how advancing these techniques can lead to genetics-guided discovery of novel chemical structures and reactions distributed throughout the tree of life. Ultimately, we discuss the advantage of increasing the known biosynthetic space to ease access to complex natural and non-natural small molecules.
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Affiliation(s)
- Jack G Ganley
- Department of Chemistry, Duke University, 124 Science Drive, Durham, NC 27708-0346, USA
| | - Emily R Derbyshire
- Department of Chemistry, Duke University, 124 Science Drive, Durham, NC 27708-0346, USA
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, 213 Research Drive, Durham, NC 27710, USA
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16
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Dionísio G, Faleiro F, Bispo R, Lopes AR, Cruz S, Paula JR, Repolho T, Calado R, Rosa R. Distinct Bleaching Resilience of Photosynthetic Plastid-Bearing Mollusks Under Thermal Stress and High CO 2 Conditions. Front Physiol 2018; 9:1675. [PMID: 30555338 PMCID: PMC6284066 DOI: 10.3389/fphys.2018.01675] [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] [Received: 08/01/2018] [Accepted: 11/08/2018] [Indexed: 11/29/2022] Open
Abstract
The impact of temperature on photo-symbiotic relationships has been highly studied in the tropical reef-forming corals but overlooked in less charismatic groups such as solar-powered sacoglossan sea slugs. These organisms display one of the most puzzling symbiotic features observed in the animal kingdom, i.e., their mollusk-plastid association, which enables them to retain photosynthetic active chloroplasts (i.e., kleptoplasts) retrieved from their algae feed sources. Here we analyze the impact of thermal stress (+4°C) and high pCO2 conditions (ΔpH = 0.4) in survival, photophysiology (i.e., bleaching, photosynthetic efficiency, and metabolism) and stress defense mechanisms (i.e., heat shock and antioxidant response) of solar-powered sacoglossan sea slugs, from tropical (Elysia crispata) and temperate (E. viridis) environments. High temperature was the main factor affecting the survival of both species, while pH only affected the survival of the temperate model. The photobiology of E. viridis remained stable under the combined scenario, while photoinhibition was observed for E. crispata under high temperature and high pCO2. In fact, bleaching was observed within all tropical specimens exposed to warming (but not in the temperate ones), which constitutes the first report where the incidence of bleaching in tropical animals hosting photosynthetic symbionts, other than corals, occurs. Yet, the expulsion of kleptoplasts by the tropical sea slug, allied with metabolic depression, constituted a physiological response that did not imply signs of vulnerability (i.e., mortality) in the host itself. Although the temperate species revealed greater heat shock and antioxidant enzyme response to environmental stress, we argue that the tropical (stenotherm) sea slug species may display a greater scope for acclimatization than the temperate (eurytherm) sea slug. E. crispata may exhibit increased capacity for phenotypic plasticity by increasing fitness in a much narrower thermal niche (minimizing maintenance costs), which ultimately may allow to face severe environmental conditions more effectively than its temperate generalist counterpart (E. viridis).
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Affiliation(s)
- Gisela Dionísio
- MARE – Marine and Environmental Sciences Centre, Laboratório Marítimo da Guia – Faculdade de Ciências da Universidade de Lisboa, Cascais, Portugal
- Departamento de Biologia & CESAM & ECOMARE, Universidade de Aveiro, Aveiro, Portugal
- Naturalist Science & Tourism, Horta, Portugal
| | - Filipa Faleiro
- MARE – Marine and Environmental Sciences Centre, Laboratório Marítimo da Guia – Faculdade de Ciências da Universidade de Lisboa, Cascais, Portugal
| | - Regina Bispo
- Departamento de Matemática, Centro de Matemática e Aplicações, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Costa de Caparica, Portugal
| | - Ana Rita Lopes
- MARE – Marine and Environmental Sciences Centre, Laboratório Marítimo da Guia – Faculdade de Ciências da Universidade de Lisboa, Cascais, Portugal
| | - Sónia Cruz
- Departamento de Biologia & CESAM & ECOMARE, Universidade de Aveiro, Aveiro, Portugal
| | - José Ricardo Paula
- MARE – Marine and Environmental Sciences Centre, Laboratório Marítimo da Guia – Faculdade de Ciências da Universidade de Lisboa, Cascais, Portugal
| | - Tiago Repolho
- MARE – Marine and Environmental Sciences Centre, Laboratório Marítimo da Guia – Faculdade de Ciências da Universidade de Lisboa, Cascais, Portugal
| | - Ricardo Calado
- Departamento de Biologia & CESAM & ECOMARE, Universidade de Aveiro, Aveiro, Portugal
| | - Rui Rosa
- MARE – Marine and Environmental Sciences Centre, Laboratório Marítimo da Guia – Faculdade de Ciências da Universidade de Lisboa, Cascais, Portugal
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Christa G, Pütz L, Sickinger C, Melo Clavijo J, Laetz EMJ, Greve C, Serôdio J. Photoprotective Non-photochemical Quenching Does Not Prevent Kleptoplasts From Net Photoinactivation. Front Ecol Evol 2018. [DOI: 10.3389/fevo.2018.00121] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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18
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Melo Clavijo J, Donath A, Serôdio J, Christa G. Polymorphic adaptations in metazoans to establish and maintain photosymbioses. Biol Rev Camb Philos Soc 2018; 93:2006-2020. [PMID: 29808579 DOI: 10.1111/brv.12430] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2017] [Revised: 04/30/2018] [Accepted: 05/02/2018] [Indexed: 12/21/2022]
Abstract
Mutualistic symbioses are common throughout the animal kingdom. Rather unusual is a form of symbiosis, photosymbiosis, where animals are symbiotic with photoautotrophic organisms. Photosymbiosis is found among sponges, cnidarians, flatworms, molluscs, ascidians and even some amphibians. Generally the animal host harbours a phototrophic partner, usually a cyanobacteria or a unicellular alga. An exception to this rule is found in some sea slugs, which only retain the chloroplasts of the algal food source and maintain them photosynthetically active in their own cytosol - a phenomenon called 'functional kleptoplasty'. Research has focused largely on the biodiversity of photosymbiotic species across a range of taxa. However, many questions with regard to the evolution of the ability to establish and maintain a photosymbiosis are still unanswered. To date, attempts to understand genome adaptations which could potentially lead to the evolution of photosymbioses have only been performed in cnidarians. This knowledge gap for other systems is mainly due to a lack of genetic information, both for non-symbiotic and symbiotic species. Considering non-photosymbiotic species is, however, important to understand the factors that make symbiotic species so unique. Herein we provide an overview of the diversity of photosymbioses across the animal kingdom and discuss potential scenarios for the evolution of this association in different lineages. We stress that the evolution of photosymbiosis is probably based on genome adaptations, which (i) lead to recognition of the symbiont to establish the symbiosis, and (ii) are needed to maintain the symbiosis. We hope to stimulate research involving sequencing the genomes of various key taxa to increase the genomic resources needed to understand the most fundamental question: how have animals evolved the ability to establish and maintain a photosymbiosis?
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Affiliation(s)
- Jenny Melo Clavijo
- Center for Molecular Biodiversity Research (zmb), Zoological Research Museum Alexander Koenig, Adenauerallee 160, Bonn, 53113, Germany
| | - Alexander Donath
- Center for Molecular Biodiversity Research (zmb), Zoological Research Museum Alexander Koenig, Adenauerallee 160, Bonn, 53113, Germany
| | - João Serôdio
- Department of Biology and Center for Environmental and Marine Studies, University of Aveiro, Campus Santiago, Aveiro, 3810-192, Portugal
| | - Gregor Christa
- Center for Molecular Biodiversity Research (zmb), Zoological Research Museum Alexander Koenig, Adenauerallee 160, Bonn, 53113, Germany.,Department of Biology and Center for Environmental and Marine Studies, University of Aveiro, Campus Santiago, Aveiro, 3810-192, Portugal
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Laetz EMJ, Wägele H. How does temperature affect functional kleptoplasty? Comparing populations of the solar-powered sister-species Elysia timida Risso, 1818 and Elysia cornigera Nuttall, 1989 (Gastropoda: Sacoglossa). Front Zool 2018; 15:17. [PMID: 29760759 PMCID: PMC5937827 DOI: 10.1186/s12983-018-0264-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2017] [Accepted: 04/06/2018] [Indexed: 01/03/2023] Open
Abstract
Background Despite widespread interest in solar-powered sea slugs (Sacoglossa: Gastropoda), relatively little is know about how they actually perform functional kleptoplasty. Sister-taxa Elysia timida and E. cornigera provide an ideal model system for investigating this phenomenon, since they feed on the same algal genus and only E. timida is capable of long-term kleptoplasty. Recent research has explored factors regarding functional kleptoplasty in E. timida, including their starvation longevity, digestive activity, autophagal response and photosynthetic efficiency under two different temperature conditions (18 °C and 21 °C). These studies revealed the trends E. timida displays regarding each factor during starvation as well as influences temperature has on some aspects of functional kleptoplasty. This study examines E. cornigera regarding each of these factors in an attempt to elucidate differences between each species that could explain their differing kleptoplastic abilities. Since both species naturally occur in 25 °C seawater (E. timida peak summer temperature, E. cornigera low winter temperature), each species was acclimatized to 25 °C to facilitate comparison and determine if these species exhibit physiological differences to starvation when under the same environmental conditions. Results When comparing the different E. timida temperature treatments, it becomes clear that increased temperatures compromise E. timida’s kleptoplastic abilities. Specimens acclimatized to 25 °C revealed shorter starvation longevities surviving an average 42.4 days compared to the 95.9 day average observed in specimens exposed to 18 °C. Each temperature treatment displayed a significantly different decrease throughout the starvation period in both, the rate of photosynthetic efficiency and in the decreasing functional kleptoplast abundance. Lysosomal abundances are assessed here as indicators of different aspects of metabolic activity, which could be correlated to temperature. E. cornigera, also acclimatized to 25 °C did not display significantly similar patterns as any of the E. timida temperature treatments, having fewer incorporated kleptoplasts, a higher lysosomal response to starvation, a faster decrease in photosynthetic efficiency and a lower starvation longevity. Conclusions These results confirm that each species has different physiological reactions to starvation and kleptoplast retention, even under the same conditions. While temperature affects aspects of functional kleptoplasty, it is likely not responsible for the differences in kleptoplastic abilities seen in these species. Electronic supplementary material The online version of this article (10.1186/s12983-018-0264-y) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Elise Marie Jerschabek Laetz
- 1Zoological Research Museum Alexander Koenig, 160 Adenauerallee, 53113 Bonn, Germany.,2Institute for Evolutionary Biology and Ecology, University of Bonn, An der Immenburg 1, 53121 Bonn, Germany
| | - Heike Wägele
- 1Zoological Research Museum Alexander Koenig, 160 Adenauerallee, 53113 Bonn, Germany
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20
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Laetz EMJ, Wägele H. Chloroplast digestion and the development of functional kleptoplasty in juvenile Elysia timida (Risso, 1818) as compared to short-term and non-chloroplast-retaining sacoglossan slugs. PLoS One 2017; 12:e0182910. [PMID: 29020043 PMCID: PMC5636068 DOI: 10.1371/journal.pone.0182910] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2017] [Accepted: 07/26/2017] [Indexed: 01/13/2023] Open
Abstract
Sacoglossan sea slugs are the only metazoans known to perform functional kleptoplasty, the sequestration and retention of functional chloroplasts within their digestive gland cells. Remarkably, a few species with this ability can survive starvation periods of 3–12 months likely due to their stolen chloroplasts. There are no reports of kleptoplast transfer from mother slug to either eggs or juveniles, demonstrating that each animal must independently acquire its kleptoplasts and develop the ability to maintain them within its digestive gland. We present here an investigation into the development of functional kleptoplasty in a long-term kleptoplast retaining species, Elysia timida. Laboratory-reared juvenile slugs of different post-metamorphic ages were placed in starvation and compared to 5 known short-term retaining slug species and 5 non-retaining slug species. The subsequent results indicate that functional kleptoplasty is not performed by E. timida until after 15 days post-metamorphosis and that by 25 days, these animals outlive many of the short-term retention species. Digestive activity was also monitored using lysosomal abundance as an indicator, revealing different patterns in starving juveniles versus adults. Starved juveniles were reintroduced to food to determine any differences in digestive activity when starvation ends, resulting in an increase in the number of kleptoplasts, but no overall change in lysosomal activity. By revealing some of the changes that occur during early development in these animals, which begin as non-kleptoplast-retaining and grow into long-term retaining slugs, this investigation provides a basis for future inquiries into the origin and development of this remarkable ability.
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Affiliation(s)
- Elise Marie Jerschabek Laetz
- Center for Molecular Biodiversity Research (ZMB), Zoological Research Museum Alexander Koenig Adenauerallee 160 Bonn, Germany
- Institute for Evolutionary Biology and Ecology, University of Bonn, An der Immenburg 1 Bonn, Germany
- * E-mail:
| | - Heike Wägele
- Center for Molecular Biodiversity Research (ZMB), Zoological Research Museum Alexander Koenig Adenauerallee 160 Bonn, Germany
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21
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Life Cycle Analysis of Endosymbiotic Algae in an Endosymbiotic Situation with Paramecium bursaria Using Capillary Flow Cytometry. ENERGIES 2017. [DOI: 10.3390/en10091413] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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22
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Rauch C, Jahns P, Tielens AGM, Gould SB, Martin WF. On Being the Right Size as an Animal with Plastids. FRONTIERS IN PLANT SCIENCE 2017; 8:1402. [PMID: 28861094 PMCID: PMC5562673 DOI: 10.3389/fpls.2017.01402] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Accepted: 07/27/2017] [Indexed: 06/07/2023]
Abstract
Plastids typically reside in plant or algal cells-with one notable exception. There is one group of multicellular animals, sea slugs in the order Sacoglossa, members of which feed on siphonaceous algae. The slugs sequester the ingested plastids in the cytosol of cells in their digestive gland, giving the animals the color of leaves. In a few species of slugs, including members of the genus Elysia, the stolen plastids (kleptoplasts) can remain morphologically intact for weeks and months, surrounded by the animal cytosol, which is separated from the plastid stroma by only the inner and outer plastid membranes. The kleptoplasts of the Sacoglossa are the only case described so far in nature where plastids interface directly with the metazoan cytosol. That makes them interesting in their own right, but it has also led to the idea that it might someday be possible to engineer photosynthetic animals. Is that really possible? And if so, how big would the photosynthetic organs of such animals need to be? Here we provide two sets of calculations: one based on a best case scenario assuming that animals with kleptoplasts can be, on a per cm2 basis, as efficient at CO2 fixation as maize leaves, and one based on 14CO2 fixation rates measured in plastid-bearing sea slugs. We also tabulate an overview of the literature going back to 1970 reporting direct measurements or indirect estimates of the CO2 fixing capabilities of Sacoglossan slugs with plastids.
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Affiliation(s)
- Cessa Rauch
- Molecular Evolution, Heinrich-Heine-UniversityDüsseldorf, Germany
| | - Peter Jahns
- Plant Biochemistry, Heinrich-Heine-UniversityDüsseldorf, Germany
| | - Aloysius G. M. Tielens
- Department of Biochemistry and Cell Biology, Faculty of Veterinary Medicine, Utrecht UniversityUtrecht, Netherlands
- Department of Medical Microbiology and Infectious Diseases, Erasmus University Medical CenterRotterdam, Netherlands
| | - Sven B. Gould
- Molecular Evolution, Heinrich-Heine-UniversityDüsseldorf, Germany
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23
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Kleptoplast photosynthesis is nutritionally relevant in the sea slug Elysia viridis. Sci Rep 2017; 7:7714. [PMID: 28798379 PMCID: PMC5552801 DOI: 10.1038/s41598-017-08002-0] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2016] [Accepted: 07/06/2017] [Indexed: 12/02/2022] Open
Abstract
Several sacoglossan sea slug species feed on macroalgae and incorporate chloroplasts into tubular cells of their digestive diverticula. We investigated the role of the “stolen” chloroplasts (kleptoplasts) in the nutrition of the sea slug Elysia viridis and assessed how their abundance, distribution and photosynthetic activity were affected by light and starvation. Elysia viridis individuals feeding on the macroalga Codium tomentosum were compared with starved specimens kept in dark and low light conditions. A combination of variable Chl a fluorescence and hyperspectral imaging, and HPLC pigment analysis was used to evaluate the spatial and temporal variability of photopigments and of the photosynthetic capacity of kleptoplasts. We show increased loss of weight and body length in dark-starved E. viridis as compared to low light-starved sea slugs. A more pronounced decrease in kleptoplast abundance and lower photosynthetic electron transport rates were observed in dark-starved sea slugs than in low light-starved animals. This study presents strong evidence of the importance of kleptoplast photosynthesis for the nutrition of E. viridis in periods of food scarcity. Deprived of photosynthates, E. viridis could accelerate the breakdown of kleptoplasts in the dark to satisfy its’ energy requirements.
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24
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Rauch C, Christa G, de Vries J, Woehle C, Gould SB. Mitochondrial Genome Assemblies of Elysia timida and Elysia cornigera and the Response of Mitochondrion-Associated Metabolism during Starvation. Genome Biol Evol 2017; 9:1873-1879. [PMID: 28854599 PMCID: PMC5534330 DOI: 10.1093/gbe/evx129] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/08/2017] [Indexed: 12/11/2022] Open
Abstract
Some sacoglossan sea slugs sequester functional plastids (kleptoplasts) from their food, which continue to fix CO2 in a light dependent manner inside the animals. In plants and algae, plastid and mitochondrial metabolism are linked in ways that reach beyond the provision of energy-rich carbon compounds through photosynthesis, but how slug mitochondria respond to starvation or alterations in plastid biochemistry has not been explored. We assembled the mitochondrial genomes of the plastid-sequestering sea slugs Elysia timida and Elysia cornigera from RNA-Seq data that was complemented with standard sequencing of mitochondrial DNA through primer walking. Our data confirm the sister species relationship of the two Sacoglossa and from the analysis of changes in mitochondrial-associated metabolism during starvation we speculate that kleptoplasts might aid in the rerouting or recycling of reducing power independent of, yet maybe improved by, photosynthesis.
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Affiliation(s)
- Cessa Rauch
- Institute for Molecular Evolution, Heinrich-Heine-University Düsseldorf, Germany
| | - Gregor Christa
- Institute for Molecular Evolution, Heinrich-Heine-University Düsseldorf, Germany
- Department of Biology and CESAM, University of Aveiro, Portugal
| | - Jan de Vries
- Institute for Molecular Evolution, Heinrich-Heine-University Düsseldorf, Germany
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Christian Woehle
- Institute for Genomic Microbiology, Christian-Albrechts-University Kiel, Germany
| | - Sven B. Gould
- Institute for Molecular Evolution, Heinrich-Heine-University Düsseldorf, Germany
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25
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Greve C, Ruiz-Tagle Lui M, Sivalingam S, Ludwig KU, Wägele H, Donath A. The complete mitochondrial genome of the 'solar-powered' sea slug Plakobranchus cf. ocellatus (Heterobranchia: Panpulmonata: Sacoglossa). MITOCHONDRIAL DNA PART B-RESOURCES 2017; 2:130-131. [PMID: 33473741 PMCID: PMC7799614 DOI: 10.1080/23802359.2016.1247667] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
We present the complete mitochondrial genome sequence of Plakobranchus cf. ocellatus (Heterobranchia: Sacoglossa), a so-called ‘solar-powered’ sea slug with long-term retention of chloroplasts. The mitochondrial genome was 14,177 bp in length containing the standard set of 13 protein-coding genes, 2 rRNAs, and 22 tRNAs. The base composition of 27.3% A, 15.6% C, 18.6% G, and 38.5% T showed a strong A + T bias. The genome organization of P. cf. ocellatus is identical to the other sacoglossan mitogenomes sequenced so far, except for Ascobulla fragilis.
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Affiliation(s)
- Carola Greve
- Zoological Research Museum Alexander Koenig (ZFMK), Centre for Molecular Biodiversity Research (zmb), Bonn, Germany
| | - Maximiliano Ruiz-Tagle Lui
- Zoological Research Museum Alexander Koenig (ZFMK), Centre for Molecular Biodiversity Research (zmb), Bonn, Germany
| | - Sugirthan Sivalingam
- Life & Brain Center, Department of Genomics, University of Bonn, Bonn, Germany.,Institute of Human Genetics, University of Bonn, Bonn, Germany
| | - Kerstin U Ludwig
- Life & Brain Center, Department of Genomics, University of Bonn, Bonn, Germany.,Institute of Human Genetics, University of Bonn, Bonn, Germany
| | - Heike Wägele
- Zoological Research Museum Alexander Koenig (ZFMK), Centre for Molecular Biodiversity Research (zmb), Bonn, Germany
| | - Alexander Donath
- Zoological Research Museum Alexander Koenig (ZFMK), Centre for Molecular Biodiversity Research (zmb), Bonn, Germany
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Laetz EMJ, Moris VC, Moritz L, Haubrich AN, Wägele H. Photosynthate accumulation in solar-powered sea slugs - starving slugs survive due to accumulated starch reserves. Front Zool 2017; 14:4. [PMID: 28115976 PMCID: PMC5244517 DOI: 10.1186/s12983-016-0186-5] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2016] [Accepted: 12/18/2016] [Indexed: 01/08/2023] Open
Abstract
Background Solar-powered sea slugs are famed for their ability to survive starvation due to incorporated algal chloroplasts. It is well established that algal-derived carbon can be traced in numerous slug-derived compounds, showing that slugs utilize the photosynthates produced by incorporated plastids. Recently, a new hypothesis suggests that the photosynthates produced are not continuously made available to the slug. Instead, at least some of the plastid’s photosynthetic products are stored in the plastid itself and only later become available to the slug. The long-term plastid-retaining slug, Elysia timida and its sole food source, Acetabularia acetabulum were examined to determine whether or not starch, a combination of amylose and amylopectin and the main photosynthate produced by A. acetabulum, is produced by the stolen plastids and whether it accumulates within individual kleptoplasts, providing an energy larder, made available to the slug at a later time. Results Histological sections of Elysia timida throughout a starvation period were stained with Lugol’s Iodine solution, a well-known stain for starch granules in plants. We present here for the first time, an increase in amylose concentration, within the slug’s digestive gland cells during a starvation period, followed by a sharp decrease. Chemically blocking photosynthesis in these tissues resulted in no observable starch, indicating that the starch in untreated animals is a product of photosynthetic activity. Conclusion This suggests that kleptoplasts function as both, a nutritive producer and storage device, holding onto the polysaccharides they produce for a certain time until they are finally available and used by the starving slug to withstand extended starvation periods.
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Affiliation(s)
- Elise M J Laetz
- Zoological Research Museum Alexander Koenig, 162 Adenauerallee, Bonn, 53113 Germany.,Institute for Evolutionary Biology and Ecology, University of Bonn, An der Immenburg 1, Bonn, 53121 Germany
| | - Victoria C Moris
- Zoological Research Museum Alexander Koenig, 162 Adenauerallee, Bonn, 53113 Germany
| | - Leif Moritz
- Zoological Research Museum Alexander Koenig, 162 Adenauerallee, Bonn, 53113 Germany
| | - André N Haubrich
- Zoological Research Museum Alexander Koenig, 162 Adenauerallee, Bonn, 53113 Germany
| | - Heike Wägele
- Zoological Research Museum Alexander Koenig, 162 Adenauerallee, Bonn, 53113 Germany
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Takahashi T. Simultaneous Evaluation of Life Cycle Dynamics between a Host Paramecium and the Endosymbionts of Paramecium bursaria Using Capillary Flow Cytometry. Sci Rep 2016; 6:31638. [PMID: 27531180 PMCID: PMC4987690 DOI: 10.1038/srep31638] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2016] [Accepted: 07/22/2016] [Indexed: 01/16/2023] Open
Abstract
Endosymbioses are driving forces underlying cell evolution. The endosymbiosis exhibited by Paramecium bursaria is an excellent model with which to study symbiosis. A single-cell microscopic analysis of P. bursaria reveals that endosymbiont numbers double when the host is in the division phase. Consequently, endosymbionts must arrange their cell cycle schedule if the culture-condition-dependent change delays the generation time of P. bursaria. However, it remains poorly understood whether endosymbionts keep pace with the culture-condition-dependent behaviors of P. bursaria, or not. Using microscopy and flow cytometry, this study investigated the life cycle behaviors occurring between endosymbionts and the host. To establish a connection between the host cell cycle and endosymbionts comprehensively, multivariate analysis was applied. The multivariate analysis revealed important information related to regulation between the host and endosymbionts. Results show that dividing endosymbionts underwent transition smoothly from the division phase to interphase, when the host was in the logarithmic phase. In contrast, endosymbiont division stagnated when the host was in the stationary phase. This paper explains that endosymbionts fine-tune their cell cycle pace with their host and that a synchronous life cycle between the endosymbionts and the host is guaranteed in the symbiosis of P. bursaria.
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Affiliation(s)
- Toshiyuki Takahashi
- Department of Chemical Science and Engineering, National Institute of Technology, Miyakonojo College, Miyazaki, Japan
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28
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Ishikawa M, Yuyama I, Shimizu H, Nozawa M, Ikeo K, Gojobori T. Different Endosymbiotic Interactions in Two Hydra Species Reflect the Evolutionary History of Endosymbiosis. Genome Biol Evol 2016; 8:2155-63. [PMID: 27324918 PMCID: PMC4987108 DOI: 10.1093/gbe/evw142] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Endosymbiosis is an important evolutionary event for organisms, and there is widespread interest in understanding the evolution of endosymbiosis establishment. Hydra is one of the most suitable organisms for studying the evolution of endosymbiosis. Within the genus Hydra, H. viridissima and H. vulgaris show endosymbiosis with green algae. Previous studies suggested that the endosymbiosis in H. vulgaris took place much more recently than that in H. viridissima, noting that the establishment of the interaction between H. vulgaris and its algae is not as stable as in H. viridissima. To investigate the on-going process of endosymbiosis, we first compared growth and tolerance to starvation in symbiotic and aposymbiotic polyps of both species. The results revealed that symbiotic H. viridissima had a higher growth rate and greater tolerance to starvation than aposymbiotic polyps. By contrast, growth of symbiotic H. vulgaris was identical to that of aposymbiotic polyps, and symbiotic H. vulgaris was less tolerant to starvation. Moreover, our gene expression analysis showed a pattern of differential gene expression in H. viridissima similar to that in other endosymbiotically established organisms, and contrary to that observed in H. vulgaris. We also showed that H. viridissima could cope with oxidative stress that caused damage, such as cell death, in H. vulgaris. These observations support the idea that oxidative stress related genes play an important role in the on-going process of endosymbiosis evolution. The different evolutionary stages of endosymbiosis studied here provide a deeper insight into the evolutionary processes occurring toward a stable endosymbiosis.
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Affiliation(s)
- Masakazu Ishikawa
- Department of Genetics, SOKENDAI, Yata, Mishima, Shizuoka, Japan Center for Information Biology, National Institute of Genetics, Yata, Mishima, Shizuoka, Japan
| | - Ikuko Yuyama
- Center for Information Biology, National Institute of Genetics, Yata, Mishima, Shizuoka, Japan
| | - Hiroshi Shimizu
- King Abdullah University of Science and Technology (KAUST), Computational Bioscience Research Center, Thuwal, Kingdom of Saudi Arabia
| | - Masafumi Nozawa
- Department of Genetics, SOKENDAI, Yata, Mishima, Shizuoka, Japan Center for Information Biology, National Institute of Genetics, Yata, Mishima, Shizuoka, Japan
| | - Kazuho Ikeo
- Department of Genetics, SOKENDAI, Yata, Mishima, Shizuoka, Japan Center for Information Biology, National Institute of Genetics, Yata, Mishima, Shizuoka, Japan
| | - Takashi Gojobori
- King Abdullah University of Science and Technology (KAUST), Computational Bioscience Research Center, Thuwal, Kingdom of Saudi Arabia
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29
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Rauch C, Vries JD, Rommel S, Rose LE, Woehle C, Christa G, Laetz EM, Wägele H, Tielens AGM, Nickelsen J, Schumann T, Jahns P, Gould SB. Why It Is Time to Look Beyond Algal Genes in Photosynthetic Slugs. Genome Biol Evol 2015; 7:2602-7. [PMID: 26319575 PMCID: PMC4607529 DOI: 10.1093/gbe/evv173] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Eukaryotic organelles depend on nuclear genes to perpetuate their biochemical integrity. This is true for mitochondria in all eukaryotes and plastids in plants and algae. Then how do kleptoplasts, plastids that are sequestered by some sacoglossan sea slugs, survive in the animals’ digestive gland cells in the absence of the algal nucleus encoding the vast majority of organellar proteins? For almost two decades, lateral gene transfer (LGT) from algae to slugs appeared to offer a solution, but RNA-seq analysis, later supported by genome sequencing of slug DNA, failed to find any evidence for such LGT events. Yet, isolated reports continue to be published and are readily discussed by the popular press and social media, making the data on LGT and its support for kleptoplast longevity appear controversial. However, when we take a sober look at the methods used, we realize that caution is warranted in how the results are interpreted. There is no evidence that the evolution of kleptoplasty in sea slugs involves LGT events. Based on what we know about photosystem maintenance in embryophyte plastids, we assume kleptoplasts depend on nuclear genes. However, studies have shown that some isolated algal plastids are, by nature, more robust than those of land plants. The evolution of kleptoplasty in green sea slugs involves many promising and unexplored phenomena, but there is no evidence that any of these require the expression of slug genes of algal origin.
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Affiliation(s)
- Cessa Rauch
- Molecular Evolution, Heinrich-Heine-University Düsseldorf, Germany
| | - Jan de Vries
- Molecular Evolution, Heinrich-Heine-University Düsseldorf, Germany
| | - Sophie Rommel
- Population Genetics, Heinrich-Heine-University Düsseldorf, Germany
| | - Laura E Rose
- Population Genetics, Heinrich-Heine-University Düsseldorf, Germany
| | - Christian Woehle
- Institut für Allgemeine Mikrobiologie, Christian-Albrechts-Universität ZMB, Am Botanischen Garten, Kiel, Germany
| | - Gregor Christa
- Molecular Evolution, Heinrich-Heine-University Düsseldorf, Germany
| | - Elise M Laetz
- Zoologisches Forschungsmuseum Alexander Koenig, Bonn, Germany
| | - Heike Wägele
- Zoologisches Forschungsmuseum Alexander Koenig, Bonn, Germany
| | - Aloysius G M Tielens
- Department of Biochemistry and Cell Biology, Faculty of Veterinary Medicine, Utrecht University, The Netherlands Department of Medical Microbiology and Infectious Diseases, Erasmus University Medical Center, Rotterdam, The Netherlands
| | | | - Tobias Schumann
- Plant Biochemistry and Stress Physiology, Heinrich-Heine-University Düsseldorf, Germany
| | - Peter Jahns
- Plant Biochemistry and Stress Physiology, Heinrich-Heine-University Düsseldorf, Germany
| | - Sven B Gould
- Molecular Evolution, Heinrich-Heine-University Düsseldorf, Germany
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30
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Kim JI, Yoon HS, Yi G, Kim HS, Yih W, Shin W. The Plastid Genome of the Cryptomonad Teleaulax amphioxeia. PLoS One 2015; 10:e0129284. [PMID: 26047475 PMCID: PMC4457928 DOI: 10.1371/journal.pone.0129284] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2015] [Accepted: 05/06/2015] [Indexed: 12/24/2022] Open
Abstract
Teleaulax amphioxeia is a photosynthetic unicellular cryptophyte alga that is distributed throughout marine habitats worldwide. This alga is an important plastid donor to the dinoflagellate Dinophysis caudata through the ciliate Mesodinium rubrum in the marine food web. To better understand the genomic characteristics of T. amphioxeia, we have sequenced and analyzed its plastid genome. The plastid genome sequence of T. amphioxeia is similar to that of Rhodomonas salina, and they share significant synteny. This sequence exhibits less similarity to that of Guillardia theta, the representative plastid genome of photosynthetic cryptophytes. The gene content and order of the three photosynthetic cryptomonad plastid genomes studied is highly conserved. The plastid genome of T. amphioxeia is composed of 129,772 bp and includes 143 protein-coding genes, 2 rRNA operons and 30 tRNA sequences. The DNA polymerase III gene (dnaX) was most likely acquired via lateral gene transfer (LGT) from a firmicute bacterium, identical to what occurred in R. salina. On the other hand, the psbN gene was independently encoded by the plastid genome without a reverse transcriptase gene as an intron. To clarify the phylogenetic relationships of the algae with red-algal derived plastids, phylogenetic analyses of 32 taxa were performed, including three previously sequenced cryptophyte plastid genomes containing 93 protein-coding genes. The stramenopiles were found to have branched out from the Chromista taxa (cryptophytes, haptophytes, and stramenopiles), while the cryptophytes and haptophytes were consistently grouped into sister relationships with high resolution.
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Affiliation(s)
- Jong Im Kim
- Department of Biology, Chungnam National University, Daejeon, Korea
| | - Hwan Su Yoon
- Department of Biological Sciences, Sungkyunkwan University, Suwon, Korea
| | - Gangman Yi
- Department of Computer Science, Gangneung-Wonju National University, Wonju, Korea
| | - Hyung Seop Kim
- Department of Marine Biotechnology, Kunsan National University, Kunsan, Korea
| | - Wonho Yih
- Department of Marine Biotechnology, Kunsan National University, Kunsan, Korea
- * E-mail: (WY); (WS)
| | - Woongghi Shin
- Department of Biology, Chungnam National University, Daejeon, Korea
- * E-mail: (WY); (WS)
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