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Dicyemid Mesozoans: A Unique Parasitic Lifestyle and a Reduced Genome

Dicyemids, previously called “mesozoans” (intermediates between unicellular protozoans and multicellular metazoans), are an enigmatic animal group. They have a highly simplified adult body, comprising only ∼30 cells, and they have a unique parasitic lifestyle. Recently, dicyemids were shown to be sp...

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Autores principales: Lu, Tsai-Ming, Kanda, Miyuki, Furuya, Hidetaka, Satoh, Noriyuki
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Oxford University Press 2019
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6736024/
https://www.ncbi.nlm.nih.gov/pubmed/31347665
http://dx.doi.org/10.1093/gbe/evz157
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author Lu, Tsai-Ming
Kanda, Miyuki
Furuya, Hidetaka
Satoh, Noriyuki
author_facet Lu, Tsai-Ming
Kanda, Miyuki
Furuya, Hidetaka
Satoh, Noriyuki
author_sort Lu, Tsai-Ming
collection PubMed
description Dicyemids, previously called “mesozoans” (intermediates between unicellular protozoans and multicellular metazoans), are an enigmatic animal group. They have a highly simplified adult body, comprising only ∼30 cells, and they have a unique parasitic lifestyle. Recently, dicyemids were shown to be spiralians, with affinities to the Platyhelminthes. In order to understand molecular mechanisms involved in evolution of this odd animal, we sequenced the genome of Dicyema japonicum and a reference transcriptome assembly using mixed-stage samples. The D. japonicum genome features a high proportion of repetitive sequences that account for 49% of the genome. The dicyemid genome is reduced to ∼67.5 Mb with 5,012 protein-coding genes. Only four Hox genes exist in the genome, with no clustering. Gene distribution in KEGG pathways shows that D. japonicum has fewer genes in most pathways. Instead of eliminating entire critical metabolic pathways, parasitic lineages likely simplify pathways by eliminating pathway-specific genes, while genes with fundamental functions may be retained in multiple pathways. In principle, parasites can stand to lose genes that are unnecessary, in order to conserve energy. However, whether retained genes in incomplete pathways serve intermediate functions and how parasites overcome the physiological needs served by lost genes, remain to be investigated in future studies.
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spelling pubmed-67360242019-09-16 Dicyemid Mesozoans: A Unique Parasitic Lifestyle and a Reduced Genome Lu, Tsai-Ming Kanda, Miyuki Furuya, Hidetaka Satoh, Noriyuki Genome Biol Evol Research Article Dicyemids, previously called “mesozoans” (intermediates between unicellular protozoans and multicellular metazoans), are an enigmatic animal group. They have a highly simplified adult body, comprising only ∼30 cells, and they have a unique parasitic lifestyle. Recently, dicyemids were shown to be spiralians, with affinities to the Platyhelminthes. In order to understand molecular mechanisms involved in evolution of this odd animal, we sequenced the genome of Dicyema japonicum and a reference transcriptome assembly using mixed-stage samples. The D. japonicum genome features a high proportion of repetitive sequences that account for 49% of the genome. The dicyemid genome is reduced to ∼67.5 Mb with 5,012 protein-coding genes. Only four Hox genes exist in the genome, with no clustering. Gene distribution in KEGG pathways shows that D. japonicum has fewer genes in most pathways. Instead of eliminating entire critical metabolic pathways, parasitic lineages likely simplify pathways by eliminating pathway-specific genes, while genes with fundamental functions may be retained in multiple pathways. In principle, parasites can stand to lose genes that are unnecessary, in order to conserve energy. However, whether retained genes in incomplete pathways serve intermediate functions and how parasites overcome the physiological needs served by lost genes, remain to be investigated in future studies. Oxford University Press 2019-07-26 /pmc/articles/PMC6736024/ /pubmed/31347665 http://dx.doi.org/10.1093/gbe/evz157 Text en © The Author(s) 2019. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution. http://creativecommons.org/licenses/by/4.0/ This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.
spellingShingle Research Article
Lu, Tsai-Ming
Kanda, Miyuki
Furuya, Hidetaka
Satoh, Noriyuki
Dicyemid Mesozoans: A Unique Parasitic Lifestyle and a Reduced Genome
title Dicyemid Mesozoans: A Unique Parasitic Lifestyle and a Reduced Genome
title_full Dicyemid Mesozoans: A Unique Parasitic Lifestyle and a Reduced Genome
title_fullStr Dicyemid Mesozoans: A Unique Parasitic Lifestyle and a Reduced Genome
title_full_unstemmed Dicyemid Mesozoans: A Unique Parasitic Lifestyle and a Reduced Genome
title_short Dicyemid Mesozoans: A Unique Parasitic Lifestyle and a Reduced Genome
title_sort dicyemid mesozoans: a unique parasitic lifestyle and a reduced genome
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6736024/
https://www.ncbi.nlm.nih.gov/pubmed/31347665
http://dx.doi.org/10.1093/gbe/evz157
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