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Analysis of DNA repair and protection in the Tardigrade Ramazzottius varieornatus and Hypsibius dujardini after exposure to UVC radiation.

Horikawa DD, Cumbers J, Sakakibara I, Rogoff D, Leuko S, Harnoto R, Arakawa K, Katayama T, Kunieda T, Toyoda A, Fujiyama A, Rothschild LJ - PLoS ONE (2013)

Bottom Line: On the other hand, the freshwater tardigrade species Hypsibius dujardini that was used as control, showed much weaker tolerance to UVC radiation than R. varieornatus, and it did not contain a putative phrA gene sequence.The anhydrobiotes of R. varieornatus accumulated much less UVC-induced thymine dimers in DNA than hydrated one.Thus we propose that UV radiation tolerance in tardigrades is due to the both high capacities of DNA damage repair and DNA protection, a two-pronged survival strategy.

View Article: PubMed Central - PubMed

Affiliation: Biospheric Science Branch, NASA Ames Research Center, Moffett Field, California, United States of America. horikawadd@gmail.com

ABSTRACT
Tardigrades inhabiting terrestrial environments exhibit extraordinary resistance to ionizing radiation and UV radiation although little is known about the mechanisms underlying the resistance. We found that the terrestrial tardigrade Ramazzottius varieornatus is able to tolerate massive doses of UVC irradiation by both being protected from forming UVC-induced thymine dimers in DNA in a desiccated, anhydrobiotic state as well as repairing the dimers that do form in the hydrated animals. In R. varieornatus accumulation of thymine dimers in DNA induced by irradiation with 2.5 kJ/m(2) of UVC radiation disappeared 18 h after the exposure when the animals were exposed to fluorescent light but not in the dark. Much higher UV radiation tolerance was observed in desiccated anhydrobiotic R. varieornatus compared to hydrated specimens of this species. On the other hand, the freshwater tardigrade species Hypsibius dujardini that was used as control, showed much weaker tolerance to UVC radiation than R. varieornatus, and it did not contain a putative phrA gene sequence. The anhydrobiotes of R. varieornatus accumulated much less UVC-induced thymine dimers in DNA than hydrated one. It suggests that anhydrobiosis efficiently avoids DNA damage accumulation in R. varieornatus and confers better UV radiation tolerance on this species. Thus we propose that UV radiation tolerance in tardigrades is due to the both high capacities of DNA damage repair and DNA protection, a two-pronged survival strategy.

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A time course of frequency of thymine dimer formation in DNA in Hypsibius dujardini and Ramazzottius varieornatus kept under light and dark conditions following UVC irradiation in the hydrated state.(A) A dot blot image showing thymine dimer formation in the two species. (B, C) Percentage of thymine dimers formed following exposure to UVC radiation in R. varieornatus and H. dujardini respectively. Control means non-irradiated specimens. pUC 19 plasmid DNA was used as molecular standard. Each value is the mean±SD (n = 3).
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pone-0064793-g004: A time course of frequency of thymine dimer formation in DNA in Hypsibius dujardini and Ramazzottius varieornatus kept under light and dark conditions following UVC irradiation in the hydrated state.(A) A dot blot image showing thymine dimer formation in the two species. (B, C) Percentage of thymine dimers formed following exposure to UVC radiation in R. varieornatus and H. dujardini respectively. Control means non-irradiated specimens. pUC 19 plasmid DNA was used as molecular standard. Each value is the mean±SD (n = 3).

Mentions: We detected DNA repair activity in R. varieornatus irradiated with 2.5 kJ/m2 of UVC radiation in the hydrated state (Fig. 4AB). In hydrated animals of R. varieornatus, the level of thymine dimers in DNA was reduced to a similar level in non-irradiated controls in both light and dark conditions at 112 h following UVC irradiation with 2.5 kJ/m2. The data proved that R. varieornatus has ability to repair DNA lesions inflicted by UVC radiation in the hydrated state within 18 h when exposed to fluorescent light while only approximately 65% of DNA lesions were repaired at this point when the animals were kept under dark conditions. In both light and dark groups of H. dujardini, no specimens survived after irradiation, and the number of thymine dimers at 18 h after irradiation increased by approximately 50% compared at the time just after irradiation in both the groups, suggesting that new thymine dimers kept being formed by non-biological chemical reaction in dead H. dujardini. The spots shown in non-irradiated control specimens (Fig. 3A, Fig. 4A) may have resulted non-specific binding by antibodies used in the experiments.


Analysis of DNA repair and protection in the Tardigrade Ramazzottius varieornatus and Hypsibius dujardini after exposure to UVC radiation.

Horikawa DD, Cumbers J, Sakakibara I, Rogoff D, Leuko S, Harnoto R, Arakawa K, Katayama T, Kunieda T, Toyoda A, Fujiyama A, Rothschild LJ - PLoS ONE (2013)

A time course of frequency of thymine dimer formation in DNA in Hypsibius dujardini and Ramazzottius varieornatus kept under light and dark conditions following UVC irradiation in the hydrated state.(A) A dot blot image showing thymine dimer formation in the two species. (B, C) Percentage of thymine dimers formed following exposure to UVC radiation in R. varieornatus and H. dujardini respectively. Control means non-irradiated specimens. pUC 19 plasmid DNA was used as molecular standard. Each value is the mean±SD (n = 3).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3675078&req=5

pone-0064793-g004: A time course of frequency of thymine dimer formation in DNA in Hypsibius dujardini and Ramazzottius varieornatus kept under light and dark conditions following UVC irradiation in the hydrated state.(A) A dot blot image showing thymine dimer formation in the two species. (B, C) Percentage of thymine dimers formed following exposure to UVC radiation in R. varieornatus and H. dujardini respectively. Control means non-irradiated specimens. pUC 19 plasmid DNA was used as molecular standard. Each value is the mean±SD (n = 3).
Mentions: We detected DNA repair activity in R. varieornatus irradiated with 2.5 kJ/m2 of UVC radiation in the hydrated state (Fig. 4AB). In hydrated animals of R. varieornatus, the level of thymine dimers in DNA was reduced to a similar level in non-irradiated controls in both light and dark conditions at 112 h following UVC irradiation with 2.5 kJ/m2. The data proved that R. varieornatus has ability to repair DNA lesions inflicted by UVC radiation in the hydrated state within 18 h when exposed to fluorescent light while only approximately 65% of DNA lesions were repaired at this point when the animals were kept under dark conditions. In both light and dark groups of H. dujardini, no specimens survived after irradiation, and the number of thymine dimers at 18 h after irradiation increased by approximately 50% compared at the time just after irradiation in both the groups, suggesting that new thymine dimers kept being formed by non-biological chemical reaction in dead H. dujardini. The spots shown in non-irradiated control specimens (Fig. 3A, Fig. 4A) may have resulted non-specific binding by antibodies used in the experiments.

Bottom Line: On the other hand, the freshwater tardigrade species Hypsibius dujardini that was used as control, showed much weaker tolerance to UVC radiation than R. varieornatus, and it did not contain a putative phrA gene sequence.The anhydrobiotes of R. varieornatus accumulated much less UVC-induced thymine dimers in DNA than hydrated one.Thus we propose that UV radiation tolerance in tardigrades is due to the both high capacities of DNA damage repair and DNA protection, a two-pronged survival strategy.

View Article: PubMed Central - PubMed

Affiliation: Biospheric Science Branch, NASA Ames Research Center, Moffett Field, California, United States of America. horikawadd@gmail.com

ABSTRACT
Tardigrades inhabiting terrestrial environments exhibit extraordinary resistance to ionizing radiation and UV radiation although little is known about the mechanisms underlying the resistance. We found that the terrestrial tardigrade Ramazzottius varieornatus is able to tolerate massive doses of UVC irradiation by both being protected from forming UVC-induced thymine dimers in DNA in a desiccated, anhydrobiotic state as well as repairing the dimers that do form in the hydrated animals. In R. varieornatus accumulation of thymine dimers in DNA induced by irradiation with 2.5 kJ/m(2) of UVC radiation disappeared 18 h after the exposure when the animals were exposed to fluorescent light but not in the dark. Much higher UV radiation tolerance was observed in desiccated anhydrobiotic R. varieornatus compared to hydrated specimens of this species. On the other hand, the freshwater tardigrade species Hypsibius dujardini that was used as control, showed much weaker tolerance to UVC radiation than R. varieornatus, and it did not contain a putative phrA gene sequence. The anhydrobiotes of R. varieornatus accumulated much less UVC-induced thymine dimers in DNA than hydrated one. It suggests that anhydrobiosis efficiently avoids DNA damage accumulation in R. varieornatus and confers better UV radiation tolerance on this species. Thus we propose that UV radiation tolerance in tardigrades is due to the both high capacities of DNA damage repair and DNA protection, a two-pronged survival strategy.

Show MeSH
Related in: MedlinePlus