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  • 1.
    Beltran-Pardo, Eliana
    et al.
    Pontificia Universidad Javeriana, Instituto de Genética Humana, Bogotá.
    Jönsson, Ingemar
    Kristianstad University, School of Education and Environment, Avdelningen för Naturvetenskap. Kristianstad University, Forskningsmiljön Man and Biosphere Health (MABH).
    Wojcik, Andrzej
    Department of Genetics, Microbiology and Toxicology, Stockholm University.
    Haghdoost, Siamak
    Department of Genetics, Microbiology and Toxicology, Stockholm University.
    Bermúdez-Cruz, Rosa María
    4Departamento de Genéticas y Biología Molecular, Centro de Investigación y Estudios Avanzados del Instituto Politécnico Nacional - CINVESTAV, Mexico City.
    Bernal Villegas, Jaime E.
    Pontificia Universidad Javeriana, Instituto de Genética Humana, Bogotá.
    Sequence analysis of the DNA-repair gene rad51 in the tardigrades Milnesium cf. tardigradum, Hypsibius dujardini and Macrobiotus cf. harmsworthi2013In: Journal of limnology, ISSN 1129-5767, E-ISSN 1723-8633, Vol. 72, no s1, p. 80-91Article in journal (Refereed)
    Abstract [en]

    Tardigrades are known for being resistant to extreme conditions, including tolerance to ionising and UV radiation in both the hydratedand the dehydrated state. It is known that these factors may cause damage to DNA. It has recently been shown that single and double DNAstrand breaks occur when tardigrades are maintained for a long time in the anhydrobiotic state. This may suggest that perhaps tardigrades rely on efficient DNA repair mechanisms. Among all proteins that comprise the DNA repair system, recombinases such as RecA or Rad51 have a very important function: DNA exchange activity. This enzyme is used in the homologous recombination and allows repair of thedamaged strand using homologous non-damaged strands as a template. In this study, Rad51 induction was evaluated by western blot in Milnesium cf. tardigradum, after exposure to gamma radiation. The Rad51 protein was highly induced by radiation, when compared to the control. The rad51 genes were searched in three tardigrades: Milnesium cf. tardigradum, Hypsibius dujardini and Macrobiotus cf. harmsworthi. The gene sequences were obtained by preparing and sequencing transcriptome libraries for H. dujardini and M. cf. harmsworthi and designing rad51 degenerate primers specific for M. cf. tardigradum. Comparison of Rad51 putative proteins from tardigrades with other organisms showed that they are highly similar to the corresponding sequence from the nematode Trichinella spiralis. A structure-based sequence alignment from tardigrades and other organisms revealed that putative Rad51 predicted proteins from tardigrades contain the expected motifs for these important recombinases. In a cladogram tree based on this alignment, tardigrades tend to cluster together suggesting that they have selective differences in these genes that make them diverge between species. Predicted Rad51 structures from tardigrades were also compared with crystalline structure of Rad51 in Saccharomyces cerevisiae. These results reveal that S. cerevisiae Rad51 structure is very similar to that of the three analysed tardigrades. On the other hand the predicted structure of Rad51 from M. cf. harmsworthi and H. dujardini are closer related to each other, than each of them to that of M. cf. tardigradum.

  • 2.
    Bertolani, Roberto
    et al.
    Italien.
    Guidetti, Roberto
    Italien.
    Jönsson, K. Ingemar
    Lund University.
    Altiero, Tiziana
    Italien.
    Boschini, Deborah
    Rebecchi, Lorena
    Italien.
    Experiences with dormancy in tardigrades2004In: Journal of limnology, ISSN 1129-5767, E-ISSN 1723-8633, Vol. 63, no Suppl. 1, p. 16-25Article in journal (Refereed)
    Abstract [en]

    Tardigrades often colonise extreme habitats, in which they survive using both types of dormancy: quiescence and diapause. Together with nematodes and bdelloid rotifers, tardigrades are known to enter quiescence (with several forms of cryptobiosis: anhydrobiosis, cryobiosis, anoxybiosis, osmobiosis) at any stage of their life cycle, from egg to adult. Entering anhydrobiosis, tardigrades contract their body into a so-called tun, loosing most of their free and bound water (>95%), synthesizing cell protectants (e.g., trehalose, glycerol, heat shock proteins) and strongly reducing or suspending their metabolism. Our research on cryptobiosis focused on some ecological and evolutionary aspects. We evaluated: i) the long-term anhydrobiotic survival by comparing quantitative data on recovery from naturally induced desiccation in several species of tardigrades; ii) differences in survival patterns between species and populations by experimentally inducing anhydrobiosis and cryobiosis; iii) phenotypic factors affecting anhydrobiotic survival. As regards diapause, we considered encystment and eggs. Encystment involves at least the synthesis of new cuticular structures. Morphological changes during cyst formation are more complex than those involved in tun formation. We analyzed more in detail encystment processes, comparing a semiterrestrial with a limnic species. Several inter-specific differences have been identified, other than the production of two types of cysts in the semiterrestrial species. Our analysis of life history traits of a laboratory reared strain of a soil tardigrade revealed a particular hatching phenology that involved the production of both subitaneous and resting eggs. The latter need a cue to hatch (dehydration followed by re-hydration). In addition, the evolutionary meaning of dormancy in tardigrades is discussed

  • 3.
    Jönsson, Ingemar
    et al.
    Kristianstad University, School of Education and Environment, Avdelningen för Naturvetenskap. Kristianstad University, Forskningsmiljön Man and Biosphere Health (MABH).
    Beltran-Pardo, Eliana
    Pontificia Universidad Javeriana, Instituto de Genética Humana, Bogotá.
    Haghdoost, Siamak
    Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University.
    Wojcik, Andrzej
    Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University.
    Bermúdez-Cruz, Rosa María
    Centro de Investigación y Estudios Avanzados del Instituto Politécnico Nacional - CINVESTAV, Mexico City.
    Bernal Villegas, Jaime E.
    Pontificia Universidad Javeriana, Instituto de Genética Humana, Bogotá.
    Harms-Ringdahl, Mats
    Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University.
    Tolerance to gamma-irradiation in eggs of the tardigrade Richtersius coronifer depends on stage of development2013In: Journal of limnology, ISSN 1129-5767, E-ISSN 1723-8633, Vol. 72, no s1, p. 73-79Article in journal (Refereed)
    Abstract [en]

    Tardigrades are known as one of the most radiation tolerant animals on Earth, and several studies on tolerance in adult tardigrades have been published. In contrast, very few studies on radiation tolerance of embryonic stages have been reported. Here we report a study on tolerance to gamma irradiation in eggs of the eutardigrade Richtersius coronifer. Irradiation of eggs collected directly from a natural substrate (moss) showed a clear dose-response, with a steep decline in hatchability at doses up to 0.4 kGy followed by a relatively constant hatchability around 25% up to 2 kGy, and a decline to ca. 5% at 4 kGy above which no eggs hatched. Analysis of the time required for eggs to hatch after irradiation (residual development time) showed that hatching of eggs after exposure to high doses of gamma radiation was associated with short residual development time. Since short residual development time means that the egg was irradiated at a late developmental stage, this suggests that eggs were more tolerant to radiation late in development. This was also confirmed in another experiment in which stage of development at irradiation was controlled. No eggs irradiated at the early developmental stage hatched, and only one egg at middle stage hatched, while eggs irradiated in the late stage hatched at a rate indistinguishable from controls. This suggests that the eggs are more sensitive to radiation in the early stages of development, or that tolerance to radiation is acquired only late in development, shortly before the eggs hatch, hypotheses that are not mutually exclusive. Our study emphasizes the importance of considering specific cell cycle phases and developmental stages in studies of tolerance to radiation in tardigrades, and the potential importance of embryonic studies in revealing the mechanisms behind the radiation tolerance of tardigrades and other cryptobiotic animals.

  • 4.
    Jönsson, K. Ingemar
    Kristianstad University, School of Education and Environment, Avdelningen för Naturvetenskap. Kristianstad University, Forskningsmiljön Man and Biosphere Health (MABH).
    Long-term experimental manipulation of moisture conditions and its impact on moss-living tardigrades2007In: Journal of limnology, ISSN 1129-5767, E-ISSN 1723-8633, Vol. 66, no Suppl. 1, p. 119-125Article in journal (Refereed)
    Abstract [en]

    The effects of long-term experimentally modified hydration conditions on populations of moss-living tardigrades were investigated in a naturally dry South-Swedish alvar environment at the Island Öland. Carbonite rocks with mosses were collected from rock fences and arranged in three experimental groups: increased dehydration, increased hydration, and control. The total experimental period was 18 months, with treatments applied during two 6 month periods. The density of tardigrade populations was recorded. The total population of tardigrades, all species included, tended to be lower under watering treatment, but the difference was only marginally significant. Populations of Richtersius coronifer and Echiniscus spiniger did not respond to the treatments, while populations of Milnesium tardigradum declined under conditions of increased hydration. The density of eggs in R. coronifer was also lower in the watering treatment. Thus, no positive response to increased hydration was recorded. These results suggest that the tardigrade populations either were not limited by the amount of hydrated periods, or that some other factor(s) counteracted the expected positive response to increased hydration. All populations showed a high variability in density among different moss samples, and the rock from which a sample was taken explained a significant part of this variability. This confirms a commonly believed, but seldom quantified, high heterogeneity in density of semi-terrestrial tardigrades, also among seemingly very similar substrates.

  • 5.
    Nilsson, Charlotta
    et al.
    Division of Nuclear Physics, Department of Physics, Lund University.
    Jönsson, Ingemar
    Kristianstad University, School of Education and Environment, Avdelningen för Naturvetenskap. Kristianstad University, Forskningsmiljön Man and Biosphere Health (MABH).
    Pallon, Jan
    Division of Nuclear Physics, Department of Physics, Lund University.
    Element analysis of the eutardigrades Richtersius coronifer and Milnesium cf. asiaticum using Particle Induced X-ray Emission (PIXE)2013In: Journal of limnology, ISSN 1129-5767, E-ISSN 1723-8633, Vol. 72, no s1, p. 92-101Article in journal (Refereed)
    Abstract [en]

    Semi-terrestrial tardigrades are well-known for their tolerance to a variety of environmental extremes, including desiccation, freezing and radiation. Despite several attempts to reveal the genetic and molecular mechanisms behind the resilience of tardigrades, it is still unknown how these animals are able to maintain the integrity of their cellular components under severe stress. Quantitative or qualitative changes in molecular compounds (e.g., carbohydrates, proteins) are expected, and have been the main line of research towards understanding the tolerance of tardigrades. In radiation tolerant bacteria, a tolerance mechanism based on manganese has been proposed. We evaluate this hypothesis in tardigrades and provide the first data on element composition in desiccated and non-desiccated specimens of two eutardigrade species, Richtersius coronifer and Milnesium cf. asiaticum. A focused 2 MeV proton microbeam was utilised to determine the elemental content, distributions and concentrations, using the ion beam analytical technique particle induced X-ray emission(PIXE). The presence of six elements – phosphorus, sulphur, chlorine, potassium, calcium and iron – were confirmed in all tardigrade specimens, at levels up to a few mg g–1. However, manganese was found in less than 10% of the analysed specimens, and in low amounts, thus our study provides no evidence for the manganese hypothesis. We also show that the distributions and/or concentrations of some elements differ between the two species as well as between the dehydrated and hydrated state. In particular, very low levels of iron were found in dehydrated M. cf. asiaticum. Our analysis shows that the PIXE technique is a useful tool for investigating questions on the distribution of elements both in dehydrated and hydrated tardigrades.

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