14TH INTERNATIONAL SYMPOSIUM ON TARDIGRADA
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Maria Kamilari, Aslak Jørgensen, Morten Schiøtt, Nadja Møbjerg
Department of Biology, University of Copenhagen, Denmark
Background:
Tardigrades (water bears) are microscopic aquatic animals found worldwide in a range of habitats. They are renowned for their cryptobiotic abilities, which include tolerance towards desiccation, freezing, severe osmotic stress and possibly environmental toxicants. Cryptobiosis, defined by a reversible shut-down of metabolism, is found among a range of lifeforms. Within Animalia, species within Nematoda, Rotifera, Tardigrada and Arthropoda, exhibit cryptobiotic capabilities.
Results:
We provide two new tardigrade transcriptomes, i.e. the first transcriptome from the marine tidal heterotardigrade Echiniscoides sigismundi, which holds a unique evolutionary position within the phylum Tardigrada, as well as a transcriptome from Richtersius coronifer representing the first transcriptome within the eutardigrade family Richtersiidae. We compare the two new transcriptomes with available eutardigrade genomic data (from Hypsibius dujardini and Ramazzottius varieornatus) and also with data from six model organisms spanning a wide spectrum of evolutionary lineages (Drosophila melanogaster, Caenorhabditis elegans, Xenopus tropicalis, Danio rerio, Homo sapiens and Saccharomyces cerevisiae). The overall comparison between the tardigrades and the listed model organisms reveal that tardigrades encode more genes in several COG based functional categories (e.g. posttranslational modification, protein turnover and chaperones, defense mechanisms, translation, ribosomal structure and biogenesis, intracellular trafficking, secretion and vesicular transport, energy production and conversion, inorganic ion transport and metabolism, secondary metabolites biosynthesis, transport and catabolism). Investigating 107 gene families, our study further provides a thorough analysis of tardigrade gene content with focus on stress tolerance. Our results reveal both gene expansions and losses that to some extent are lineage specific within the phylum Tardigrada.
Conclusions:
Our results show common gene losses and expansions within stress
related gene pathways in tardigrades, but also indicate that different evolutionary lineages have a high degree of divergence involving unique molecular adaptations and possible unknown functional homologues.
Keywords: comparative transcriptomics, Heterotardigrada, model organisms, stress genes
The study was supported by The Independent Research Fund Denmark (grant-ID:DFF–4090-00145) and research grant (17522) from VILLUM FONDEN. MK is a Marie Curie fellow funded from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 747087.
Tardigrades (water bears) are microscopic aquatic animals found worldwide in a range of habitats. They are renowned for their cryptobiotic abilities, which include tolerance towards desiccation, freezing, severe osmotic stress and possibly environmental toxicants. Cryptobiosis, defined by a reversible shut-down of metabolism, is found among a range of lifeforms. Within Animalia, species within Nematoda, Rotifera, Tardigrada and Arthropoda, exhibit cryptobiotic capabilities.
Results:
We provide two new tardigrade transcriptomes, i.e. the first transcriptome from the marine tidal heterotardigrade Echiniscoides sigismundi, which holds a unique evolutionary position within the phylum Tardigrada, as well as a transcriptome from Richtersius coronifer representing the first transcriptome within the eutardigrade family Richtersiidae. We compare the two new transcriptomes with available eutardigrade genomic data (from Hypsibius dujardini and Ramazzottius varieornatus) and also with data from six model organisms spanning a wide spectrum of evolutionary lineages (Drosophila melanogaster, Caenorhabditis elegans, Xenopus tropicalis, Danio rerio, Homo sapiens and Saccharomyces cerevisiae). The overall comparison between the tardigrades and the listed model organisms reveal that tardigrades encode more genes in several COG based functional categories (e.g. posttranslational modification, protein turnover and chaperones, defense mechanisms, translation, ribosomal structure and biogenesis, intracellular trafficking, secretion and vesicular transport, energy production and conversion, inorganic ion transport and metabolism, secondary metabolites biosynthesis, transport and catabolism). Investigating 107 gene families, our study further provides a thorough analysis of tardigrade gene content with focus on stress tolerance. Our results reveal both gene expansions and losses that to some extent are lineage specific within the phylum Tardigrada.
Conclusions:
Our results show common gene losses and expansions within stress
related gene pathways in tardigrades, but also indicate that different evolutionary lineages have a high degree of divergence involving unique molecular adaptations and possible unknown functional homologues.
Keywords: comparative transcriptomics, Heterotardigrada, model organisms, stress genes
The study was supported by The Independent Research Fund Denmark (grant-ID:DFF–4090-00145) and research grant (17522) from VILLUM FONDEN. MK is a Marie Curie fellow funded from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 747087.
Investigating candidate genes of cryobiosis in the eutardigrade Ramazzottius oberhaeuseri through real-time qPCR quantification of differential expression
Marcus Deichmann1, Maria Kamilari2, Sarah B. Morgan2, Lykke K. B. Hvidepil2, Nynne Nymann2, Nadja Møbjerg2
1: DTU Bioinformatics, Technical University of Denmark, 2: Department of Biology, University of Copenhagen, Denmark
Background:
The eutardigrade Ramazzottius oberhaeuseri can survive exposure to extreme cold by reversibly entering a latent state of high tolerance, termed cryobiosis. Here we investigate candidate genes with putative association to mechanisms of cryobiotic protection of biomolecular structures,
reduction of the damaging effects of ice formation and freeze-induced cellular dehydration as well as post-cryobiotic regeneration. The expression patterns of a collection of these genes are examined in correlation to cryobiosis by employing real-time qPCR differential expression analyses to perform relative quantification of expression of active specimens in comparison to 2-hour postfrozen specimens, having been exposed to -80°C for 10 days.
Results:
In this study, significant correlations have been established between cryobiosis and upregulated expression of Secretory Abundant Heat Soluble Protein 1 (SAHS1) (3.7-fold, P<0.0001) and Cytoplasmic Abundant Heat Soluble Protein 3 (CAHS3) (3.2-fold, P<0.0001). Less significant identifications of upregulated
expression for Aquaporin-10 (AQP10) (1.6-fold, P=0.0151) and downregulated expression of a putative glucose transporter (SLC2A1) (0.6-fold, P=0.0320) were detected. Several genes did not show any differential expression in the 2-hour post-frozen state, specifically Heat Shock Protein 20 (HSP20), Heat Shock Protein 70 (HSP70) and Late Embryogenesis Abundant Protein 4 (LEA4). A more constitutive expression pattern or post-frozen reestablishment of expression is supported by the obtained results for these genes.
Conclusions:
Our results indicate important functions of the eutardigrade-specific SAHS and CAHS proteins in regard to cryoprotective mechanisms in Ramazzottius. Combined with recent findings on the structure and localization of SAHS1 from Ramazzottius varieornatus, we hypothesize that SAHS1 may have a potential importance in relation to cryobiotic survival, potentially through carboxylic acid binding in the extracellular space. Furthermore, the importance of molecular transport and osmotic processes in cryoprotection is supported by differential expression of AQP10 and SLC2A1. The results do not exclude HSP20, HSP70 and LEA4 as important elements of cryoprotection, but merely indicate constitutive expression or reestablishment 2 hours after cryobiosis.
Keywords: cryobiosis, differential gene expression, eutardigrade, real-time qPCR
This work was supported by research grant (17522) from VILLUM FONDEN. MK is a Marie Curie fellow funded from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 747087.
The eutardigrade Ramazzottius oberhaeuseri can survive exposure to extreme cold by reversibly entering a latent state of high tolerance, termed cryobiosis. Here we investigate candidate genes with putative association to mechanisms of cryobiotic protection of biomolecular structures,
reduction of the damaging effects of ice formation and freeze-induced cellular dehydration as well as post-cryobiotic regeneration. The expression patterns of a collection of these genes are examined in correlation to cryobiosis by employing real-time qPCR differential expression analyses to perform relative quantification of expression of active specimens in comparison to 2-hour postfrozen specimens, having been exposed to -80°C for 10 days.
Results:
In this study, significant correlations have been established between cryobiosis and upregulated expression of Secretory Abundant Heat Soluble Protein 1 (SAHS1) (3.7-fold, P<0.0001) and Cytoplasmic Abundant Heat Soluble Protein 3 (CAHS3) (3.2-fold, P<0.0001). Less significant identifications of upregulated
expression for Aquaporin-10 (AQP10) (1.6-fold, P=0.0151) and downregulated expression of a putative glucose transporter (SLC2A1) (0.6-fold, P=0.0320) were detected. Several genes did not show any differential expression in the 2-hour post-frozen state, specifically Heat Shock Protein 20 (HSP20), Heat Shock Protein 70 (HSP70) and Late Embryogenesis Abundant Protein 4 (LEA4). A more constitutive expression pattern or post-frozen reestablishment of expression is supported by the obtained results for these genes.
Conclusions:
Our results indicate important functions of the eutardigrade-specific SAHS and CAHS proteins in regard to cryoprotective mechanisms in Ramazzottius. Combined with recent findings on the structure and localization of SAHS1 from Ramazzottius varieornatus, we hypothesize that SAHS1 may have a potential importance in relation to cryobiotic survival, potentially through carboxylic acid binding in the extracellular space. Furthermore, the importance of molecular transport and osmotic processes in cryoprotection is supported by differential expression of AQP10 and SLC2A1. The results do not exclude HSP20, HSP70 and LEA4 as important elements of cryoprotection, but merely indicate constitutive expression or reestablishment 2 hours after cryobiosis.
Keywords: cryobiosis, differential gene expression, eutardigrade, real-time qPCR
This work was supported by research grant (17522) from VILLUM FONDEN. MK is a Marie Curie fellow funded from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 747087.