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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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Related in: MedlinePlus

Expression of the phrA gene following 2.5 kJ/m2 UVC exposure to R. varieornatusA value obtained from non-irradiated R. varieornatus was set as 1 and values were compared to this control value. Subsequent samples are compared in terms of -fold regulation to this value. Asterisks denote significant differences compared with control (One-way ANOVA; •••: P<0.001). Each value is the mean±SD (n = 3).
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pone-0064793-g006: Expression of the phrA gene following 2.5 kJ/m2 UVC exposure to R. varieornatusA value obtained from non-irradiated R. varieornatus was set as 1 and values were compared to this control value. Subsequent samples are compared in terms of -fold regulation to this value. Asterisks denote significant differences compared with control (One-way ANOVA; •••: P<0.001). Each value is the mean±SD (n = 3).

Mentions: Expression of the phrA gene was evaluated following 2.5 kJ/m2 UVC exposure to R. varieornatus. A value obtained from non-irradiated R. varieornatus was set as 1 and values were compared to this control value. A significant increase in expression level of phrA was observed only 18 h after UVC irradiation in both dark (9.1-fold) and light (7.8-fold) conditions (One-way ANOVA, P<0.001) while there was no significant differences in expression levels in 0 and 112 h after UVC exposure compared to that in non-irradiated control (One-way ANOVA, P>0.05) (Fig. 6). No significant difference in expression level of phrA was detected between dark and light conditions 18 h after UVC irradiation.


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)

Expression of the phrA gene following 2.5 kJ/m2 UVC exposure to R. varieornatusA value obtained from non-irradiated R. varieornatus was set as 1 and values were compared to this control value. Subsequent samples are compared in terms of -fold regulation to this value. Asterisks denote significant differences compared with control (One-way ANOVA; •••: P<0.001). 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-g006: Expression of the phrA gene following 2.5 kJ/m2 UVC exposure to R. varieornatusA value obtained from non-irradiated R. varieornatus was set as 1 and values were compared to this control value. Subsequent samples are compared in terms of -fold regulation to this value. Asterisks denote significant differences compared with control (One-way ANOVA; •••: P<0.001). Each value is the mean±SD (n = 3).
Mentions: Expression of the phrA gene was evaluated following 2.5 kJ/m2 UVC exposure to R. varieornatus. A value obtained from non-irradiated R. varieornatus was set as 1 and values were compared to this control value. A significant increase in expression level of phrA was observed only 18 h after UVC irradiation in both dark (9.1-fold) and light (7.8-fold) conditions (One-way ANOVA, P<0.001) while there was no significant differences in expression levels in 0 and 112 h after UVC exposure compared to that in non-irradiated control (One-way ANOVA, P>0.05) (Fig. 6). No significant difference in expression level of phrA was detected between dark and light conditions 18 h after UVC irradiation.

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