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Antioxidants & Redox Signaling Sep 2013Platyhelminth parasites cause chronic infections that are a major cause of disability, mortality, and economic losses in developing countries. Maintaining redox... (Review)
Review
SIGNIFICANCE
Platyhelminth parasites cause chronic infections that are a major cause of disability, mortality, and economic losses in developing countries. Maintaining redox homeostasis is a major adaptive problem faced by parasites and its disruption can shift the biochemical balance toward the host. Platyhelminth parasites possess a streamlined thiol-based redox system in which a single enzyme, thioredoxin glutathione reductase (TGR), a fusion of a glutaredoxin (Grx) domain to canonical thioredoxin reductase (TR) domains, supplies electrons to oxidized glutathione (GSSG) and thioredoxin (Trx). TGR has been validated as a drug target for schistosomiasis.
RECENT ADVANCES
In addition to glutathione (GSH) and Trx reduction, TGR supports GSH-independent deglutathionylation conferring an additional advantage to the TGR redox array. Biochemical and structural studies have shown that the TR activity does not require the Grx domain, while the glutathione reductase and deglutathionylase activities depend on the Grx domain, which receives electrons from the TR domains. The search for TGR inhibitors has identified promising drug leads, notably oxadiazole N-oxides.
CRITICAL ISSUES
A conspicuous feature of platyhelminth TGRs is that their Grx-dependent activities are temporarily inhibited at high GSSG concentrations. The mechanism underlying the phenomenon and its biological relevance are not completely understood.
FUTURE DIRECTIONS
The functional diversity of Trxs and Grxs encoded in platyhelminth genomes remains to be further assessed to thoroughly understand the TGR-dependent redox network. Optimization of TGR inhibitors and identification of compounds targeting other parasite redox enzymes are good options to clinically develop relevant drugs for these neglected, but important diseases.
Topics: Animals; Cestode Infections; Helminth Proteins; Host-Parasite Interactions; Humans; Metabolic Networks and Pathways; Multienzyme Complexes; NADH, NADPH Oxidoreductases; Oxidation-Reduction; Oxidative Stress; Platyhelminths; Reactive Oxygen Species
PubMed: 22909029
DOI: 10.1089/ars.2012.4670 -
Scientific Reports Nov 2023Microturbellarians are abundant and ubiquitous members of marine meiofaunal communities around the world. Because of their small body size, these microscopic animals are...
Microturbellarians are abundant and ubiquitous members of marine meiofaunal communities around the world. Because of their small body size, these microscopic animals are rarely considered as hosts for parasitic organisms. Indeed, many protists, both free-living and parasitic ones, equal or surpass meiofaunal animals in size. Despite several anecdotal records of "gregarines", "sporozoans", and "apicomplexans" parasitizing microturbellarians in the literature-some of them dating back to the nineteenth century-these single-celled parasites have never been identified and characterized. More recently, the sequencing of eukaryotic microbiomes in microscopic invertebrates have revealed a hidden diversity of protist parasites infecting microturbellarians and other meiofaunal animals. Here we show that apicomplexans isolated from twelve taxonomically diverse rhabdocoel taxa and one species of proseriate collected in four geographically distinct areas around the Pacific Ocean (Okinawa, Hokkaido, and British Columbia) and the Caribbean Sea (Curaçao) all belong to the apicomplexan genus Rhytidocystis. Based on comprehensive molecular phylogenies of Rhabdocoela and Proseriata inferred from both 18S and 28S rDNA sequences, as well as a molecular phylogeny of Marosporida inferred from 18S rDNA sequences, we determine the phylogenetic positions of the microturbellarian hosts and their parasites. Multiple lines of evidence, including morphological and molecular data, show that at least nine new species of Rhytidocystis infect the microturbellarian hosts collected in this study, more than doubling the number of previously recognized species of Rhytidocystis, all of which infect polychaete hosts. A cophylogenetic analysis examining patterns of phylosymbiosis between hosts and parasites suggests a complex picture of overall incongruence between host and parasite phylogenies, and varying degrees of geographic signals and taxon specificity.
Topics: Animals; Platyhelminths; Phylogeny; Parasites; DNA, Ribosomal; Apicomplexa
PubMed: 38030717
DOI: 10.1038/s41598-023-48233-y -
Development (Cambridge, England) Jul 2021Acoels are marine worms that belong to the phylum Xenacoelomorpha, a deep-diverging bilaterian lineage. This makes acoels an attractive system for studying the evolution...
Acoels are marine worms that belong to the phylum Xenacoelomorpha, a deep-diverging bilaterian lineage. This makes acoels an attractive system for studying the evolution of major bilaterian traits. Thus far, acoel development has not been described in detail at the morphological and transcriptomic levels in a species in which functional genetic studies are possible. We present a set of developmental landmarks for embryogenesis in the highly regenerative acoel Hofstenia miamia. We generated a developmental staging atlas from zygote to hatched worm based on gross morphology, with accompanying bulk transcriptome data. Hofstenia embryos undergo a stereotyped cleavage program known as duet cleavage, which results in two large vegetal pole 'macromeres' and numerous small animal pole 'micromeres'. These macromeres become internalized as micromere progeny proliferate and move vegetally. We also noted a second, previously undescribed, cell-internalization event at the animal pole, following which we detected major body axes and tissues corresponding to all three germ layers. Our work on Hofstenia embryos provides a resource for mechanistic investigations of acoel development, which will yield insights into the evolution of bilaterian development and regeneration.
Topics: Animals; Embryonic Development; Germ Layers; Platyhelminths; Regeneration; Transcriptome
PubMed: 34196362
DOI: 10.1242/dev.188656 -
Trends in Parasitology Dec 2011Schistosoma genomes provide a comprehensive resource for identifying the molecular processes that shape parasite evolution and for discovering novel chemotherapeutic or... (Review)
Review
Schistosoma genomes provide a comprehensive resource for identifying the molecular processes that shape parasite evolution and for discovering novel chemotherapeutic or immunoprophylactic targets. Here, we demonstrate how intragenus and intergenus comparative genomics can be used to drive these investigations forward, illustrate the advantages and limitations of these approaches and review how post-genomic technologies offer complementary strategies for genome characterisation. Although sequencing and functional characterisation of other schistosome/platyhelminth genomes continues to expedite anthelmintic discovery, we contend that future priorities should equally focus on improving assembly quality, and chromosomal assignment, of existing schistosome/platyhelminth genomes.
Topics: Animals; Anthelmintics; Chromosomes; Genome, Helminth; Genomics; Humans; Schistosoma; Schistosomiasis
PubMed: 22024648
DOI: 10.1016/j.pt.2011.09.003 -
Genome Biology and Evolution Sep 2022Polyclad flatworms are widely thought to be one of the least derived of the flatworm classes and, as such, are well placed to investigate evolutionary and developmental...
Polyclad flatworms are widely thought to be one of the least derived of the flatworm classes and, as such, are well placed to investigate evolutionary and developmental features such as spiral cleavage and larval diversification lost in other platyhelminths. Prostheceraeus crozieri, (formerly Maritigrella crozieri), is an emerging model polyclad flatworm that already has some useful transcriptome data but, to date, no sequenced genome. We have used high molecular weight DNA extraction and long-read PacBio sequencing to assemble the highly repetitive (67.9%) P. crozieri genome (2.07 Gb). We have annotated 43,325 genes, with 89.7% BUSCO completeness. Perhaps reflecting its large genome, introns were considerably larger than other free-living flatworms, but evidence of abundant transposable elements suggests genome expansion has been principally via transposable elements activity. This genome resource will be of great use for future developmental and phylogenomic research.
Topics: Animals; Base Sequence; DNA Transposable Elements; Phylogeny; Platyhelminths; Sequence Analysis, DNA
PubMed: 36040059
DOI: 10.1093/gbe/evac133 -
Philosophical Transactions of the Royal... Apr 2008Conventional wisdom suggests that bilateral organisms arose from ancestors that were radially, rather than bilaterally, symmetrical and, therefore, had a single body... (Review)
Review
Conventional wisdom suggests that bilateral organisms arose from ancestors that were radially, rather than bilaterally, symmetrical and, therefore, had a single body axis and no mesoderm. The two main hypotheses on how this transformation took place consider either a simple organism akin to the planula larva of extant cnidarians or the acoel Platyhelminthes (planuloid-acoeloid theory), or a rather complex organism bearing several or most features of advanced coelomate bilaterians (archicoelomate theory). We report phylogenetic analyses of bilaterian metazoans using quantitative (ribosomal, nuclear and expressed sequence tag sequences) and qualitative (HOX cluster genes and microRNA sets) markers. The phylogenetic trees obtained corroborate the position of acoel and nemertodermatid flatworms as the earliest branching extant members of the Bilateria. Moreover, some acoelomate and pseudocoelomate clades appear as early branching lophotrochozoans and deuterostomes. These results strengthen the view that stem bilaterians were small, acoelomate/pseudocoelomate, benthic organisms derived from planuloid-like organisms. Because morphological and recent gene expression data suggest that cnidarians are actually bilateral, the origin of the last common bilaterian ancestor has to be put back in time earlier than the cnidarian-bilaterian split in the form of a planuloid animal. A new systematic scheme for the Bilateria that includes the Cnidaria is suggested and its main implications discussed.
Topics: Animals; Bayes Theorem; Biological Evolution; Cnidaria; Evolution, Molecular; Genes, Homeobox; Genetic Markers; Invertebrates; Models, Biological; Multigene Family; Phylogeny; Platyhelminths
PubMed: 18192186
DOI: 10.1098/rstb.2007.2238 -
Parasite (Paris, France) 2023Twenty-nine dactylogyrid species were reported from teleosts collected during a survey of the parasites of fishes of Moreton Bay, Queensland, Australia, in 2016. Two new...
Species of Dactylogyridae (Platyhelminthes: Monogenoidea) infecting marine fishes of Moreton Bay, Queensland, Australia, with proposals of Pleuronectitrema n. gen. and Ecnomotrema n. gen. and descriptions of 13 new species.
Twenty-nine dactylogyrid species were reported from teleosts collected during a survey of the parasites of fishes of Moreton Bay, Queensland, Australia, in 2016. Two new genera, Ecnomotrema n. gen. and Pleuronectitrema n. gen., were proposed, and 13 new species were illustrated and described: Atherinicus difficilis n. sp., Diversohamulus similis n. sp., and Ecnomotrema cetiosum n. sp. from Atherinomorus vaigiensis; Haliotrema apiculum n. sp. from Pempheris schwenkii; Haliotrema tugulduriforme n. sp. from Scarus ghobban; Lethrinitrema australiense n. sp., and Lethrinitrema lituus n. sp. from Lethrinus nebulosus; Tetrancistrum siganioides n. sp. from Siganus fuscescens; Ligophorus bostrychus n. sp. from Planiliza subviridis; Neohaliotrema gemmula n. sp. from Abudefduf vaigiensis; Neohaliotrema moretonense n. sp. from Ab. vaigiensis and Ab. bengalensis; and Pleuronectitrema spirula n. sp. from Pseudorhombus arsius (all from Moreton Bay); Pleuronectitrema kuwaitense Kritsky & Sey n. sp. was described from specimens collected from P. arsius in Kuwait during 1996. Ten new host records were recorded: Chauhanellus duriensis Lim, 1994 and Hamatopeduncularia thalassini Bychowsky & Nagibina, 1969 from Pararius proximus; Diplectanotrema sp. 1 and sp. 2 from Sillago maculata and Goniistius vestitus, respectively; Diversohamulus tricuspidatus Bychowsky & Nagibina, 1969 from At. vaigiensis; Hal. cf. dempsteri (Mizelle & Price, 1964) Young, 1968 from Prionurus microlepidotus; Hal. spirale Yamaguti, 1968 from Upeneus tragula; Ligophorus kaohsianghsieni (Gussev, 1962) Gussev, 1985 from Planiliza subviridis; and Neohaliotrema malayense Lim & Gibson, 2010 from Ab. bengalensis and Ab. whitleyi. Twenty-five new faunal records for Moreton Bay were recorded, including the new species listed above and C. duriensis, Diplectanotrema sp. 1 and sp. 2, Diversohamulus tricuspidatus Bychowsky & Nagibina, 1969, Glyphidohaptor phractophallus Kritsky, Galli, & Yang, 2007, Hal. cf. dempsteri, Hal. johnstoni Bychowsky & Nagibina, 1970, Hal. spirale, Yamaguti, 1968 Hamatopeduncularia thalassini Bychowsky & Nagibina, 1969, Lethrinitrema nebulosum Sun, Li, & Yang, 2014, Ligophorus kaohsianghsieni (Gussev, 1962) Gussev, 1985, Ligophorus parvicopulatrix Soo & Lim, 2012, and Neohaliotrema malayense Lim & Gibson, 2010. Three new combinations were proposed: Hal. spariense Roubal, 1981 as Euryhaliotrema spariense (Roubal, 1981) n. comb.; and Hal. arsiosa Venkatanarasaiah, 1984 and Hal. youngi Venkatanarasaiah, 1984 as Pleuronectitrema arsiosa (Venkatanarasaiah, 1984) n. comb. and Pleuronectitrema youngi (Venkatanarasaiah, 1984) n. comb., respectively; Haliotrema sp. of Zhang is transferred to Pleuronectitrema as Pleuronectitrema sp. Hal. ctenochaeti Yamaguti, 1968 was replaced with Hal. asymphylum n. nom. to remove it from homonymy with Hal. ctenochaeti Young, 1968. Pseudohaliotrematoides zancli Yamaguti, 1968 was transferred to Haliotrema as Haliotrema hawaiiense n. nom. Hal. zancli Yamaguti, 1968 was considered a junior subjective synonym of Hal. dempsteri.
Topics: Animals; Queensland; Bays; Platyhelminths; Trematoda; Australia; Fishes; Smegmamorpha
PubMed: 38117271
DOI: 10.1051/parasite/2023053 -
Microbiology Spectrum Jun 2022Because parasites have an inextricable relationship with their host, they have the potential to serve as viral reservoirs or facilitate virus host shifts. And yet,...
Because parasites have an inextricable relationship with their host, they have the potential to serve as viral reservoirs or facilitate virus host shifts. And yet, little is known about viruses infecting parasitic hosts except for blood-feeding arthropods that are well-known vectors of zoonotic viruses. Herein, we uncovered viruses of flatworms (phylum Platyhelminthes, group Neodermata) that specialize in parasitizing vertebrates and their ancestral free-living relatives. We discovered 115 novel viral sequences, including 1 in Macrostomorpha, 5 in Polycladida, 44 in Tricladida, 1 in Monogenea, 15 in Cestoda, and 49 in Trematoda, through data mining. The majority of newly identified viruses constitute novel families or genera. Phylogenetic analyses show that the virome of flatworms changed dramatically during the transition of neodermatans to a parasitic lifestyle. Most Neodermata viruses seem to codiversify with their host, with the exception of rhabdoviruses, which may switch hosts more often, based on phylogenetic relationships. Neodermata rhabdoviruses also have a position ancestral to vertebrate-associated rhabdo viruses, including lyssaviruses, suggesting that vertebrate-associated rhabdoviruses emerged from a flatworm rhabdovirus in a parasitized host. This study reveals an extensive diversity of viruses in Platyhelminthes and highlights the need to evaluate the role of viral infection in flatworm-associated diseases. Little is known about the diversity of parasite-associated viruses and how these viruses may impact parasite fitness, parasite-host interactions, and virus evolution. The discovery of over a hundred viruses associated with a range of free-living and parasitic flatworms, including parasites of economic and clinical relevance, allowed us to compare the viromes of flatworms with contrasting lifestyles. The results suggest that flatworms acquired novel viruses after their transition to a parasitic lifestyle and highlight the possibility that they acquired viruses from their hosts and vice versa. An interesting example is the discovery of flatworm rhabdoviruses that have a position ancestral to rabies viruses and other vertebrate-associated rhabdoviruses, demonstrating that flatworm-associated viruses have emerged in a vertebrate host at least once in history. Therefore, parasitic flatworms may play a role in virus diversity and emergence. The roles that parasite-infecting viruses play in parasite-associated diseases remain to be investigated.
Topics: Animals; Host-Parasite Interactions; Parasites; Phylogeny; Platyhelminths; Viruses
PubMed: 35536058
DOI: 10.1128/spectrum.00138-22 -
BMC Evolutionary Biology Sep 2017Small non-coding RNAs, including miRNAs, and gene silencing mediated by RNA interference have been described in free-living and parasitic lineages of flatworms, but only...
BACKGROUND
Small non-coding RNAs, including miRNAs, and gene silencing mediated by RNA interference have been described in free-living and parasitic lineages of flatworms, but only few key factors of the small RNA pathways have been exhaustively investigated in a limited number of species. The availability of flatworm draft genomes and predicted proteomes allowed us to perform an extended survey of the genes involved in small non-coding RNA pathways in this phylum.
RESULTS
Overall, findings show that the small non-coding RNA pathways are conserved in all the analyzed flatworm linages; however notable peculiarities were identified. While Piwi genes are amplified in free-living worms they are completely absent in all parasitic species. Remarkably all flatworms share a specific Argonaute family (FL-Ago) that has been independently amplified in different lineages. Other key factors such as Dicer are also duplicated, with Dicer-2 showing structural differences between trematodes, cestodes and free-living flatworms. Similarly, a very divergent GW182 Argonaute interacting protein was identified in all flatworm linages. Contrasting to this, genes involved in the amplification of the RNAi interfering signal were detected only in the ancestral free living species Macrostomum lignano. We here described all the putative small RNA pathways present in both free living and parasitic flatworm lineages.
CONCLUSION
These findings highlight innovations specifically evolved in platyhelminths presumably associated with novel mechanisms of gene expression regulation mediated by small RNA pathways that differ to what has been classically described in model organisms. Understanding these phylum-specific innovations and the differences between free living and parasitic species might provide clues to adaptations to parasitism, and would be relevant for gene-silencing technology development for parasitic flatworms that infect hundreds of million people worldwide.
Topics: Animals; Argonaute Proteins; Caenorhabditis elegans; Chromatin Assembly and Disassembly; Gene Expression Regulation; Gene Silencing; Helminth Proteins; MicroRNAs; Platyhelminths; RNA Interference; RNA, Small Interfering; Ribonuclease III
PubMed: 28893179
DOI: 10.1186/s12862-017-1061-5 -
Proceedings. Biological Sciences Jul 2022Dicyemids and orthonectids were traditionally classified in a group called Mesozoa, but their placement in a single clade has been contested and their position(s) within...
Dicyemids and orthonectids were traditionally classified in a group called Mesozoa, but their placement in a single clade has been contested and their position(s) within Metazoa is uncertain. Here, we assembled a comprehensive matrix of Lophotrochozoa (Metazoa) and investigated the position of Dicyemida (= Rhombozoa) and Orthonectida, employing multiple phylogenomic approaches. We sequenced seven new transcriptomes and one draft genome from dicyemids (, ) and two transcriptomes from orthonectids (). Using these and published data, we assembled and analysed contamination-filtered datasets with up to 987 genes. Our results recover Mesozoa monophyletic and as a close relative of Platyhelminthes or Gnathifera. Because of the tendency of the long-branch mesozoans to group with other long-branch taxa in our analyses, we explored the impact of approaches purported to help alleviate long-branch attraction (e.g. taxon removal, coalescent inference, gene targeting). None of these were able to break the association of Orthonectida with Dicyemida in the maximum-likelihood trees. Contrastingly, the Bayesian analysis and site-specific frequency model in maximum-likelihood did not recover a monophyletic Mesozoa (but only when using a specific 50 gene matrix). The classic hypothesis on monophyletic Mesozoa is possibly reborn and should be further tested.
Topics: Animals; Base Sequence; Bayes Theorem; Invertebrates; Phylogeny; Platyhelminths
PubMed: 35858055
DOI: 10.1098/rspb.2022.0683