title: Photoreactivation is the main repair pathway for UV-induced DNA damage in coral planulae.
abstract: The larvae of most coral species spend some time in the plankton, floating just below the surface and hence exposed to high levels of ultraviolet radiation (UVR). The high levels of UVR are potentially stressful and damaging to DNA and other cellular components, such as proteins, reducing survivorship. Consequently, mechanisms to either shade (prevent) or repair damage potentially play an important role. In this study, the role of photoreactivation in the survival of coral planulae was examined. Photoreactivation is a light-stimulated response to UV-damaged DNA in which photolyase proteins repair damaged DNA. Photoreactivation rates, as well as the localization of photolyase, were explored in planulae under conditions where photoreactivation was or was not inhibited. The results indicate that photoreactivation is the main DNA repair pathway in coral planulae, repairing UV-induced DNA damage swiftly (K=1.75 h(-1) and a half-life of repair of 23 min), with no evidence of any light-independent DNA repair mechanisms, such as nucleotide excision repair (NER), at work. Photolyase mRNA was localized to both the ectoderm and endoderm of the larvae. The amount of cell death in the coral planulae increased significantly when photoreactivation was inhibited, by blocking photoreactivating light. We found that photoreactivation, along with additional UV shielding in the form of five mycosporine-like amino acids, are sufficient for survival in surface tropical waters and that planulae do not accumulate DNA damage despite being exposed to high UVR.
authors.affiliation: Centre for Marine Studies and the ARC Centre of Excellence for Coral Reef Studies, The University of Queensland, St Lucia, QLD 4072 Australia.
authors.forename: Ruth
authors.initials: R
authors.lastname: Reef
authors.forename: Simon
authors.initials: S
authors.lastname: Dunn
authors.forename: Oren
authors.initials: O
authors.lastname: Levy
authors.forename: Sophie
authors.initials: S
authors.lastname: Dove
authors.forename: Eli
authors.initials: E
authors.lastname: Shemesh
authors.forename: Itzchak
authors.initials: I
authors.lastname: Brickner
authors.forename: William
authors.initials: W
authors.lastname: Leggat
authors.forename: Ove
authors.initials: O
authors.lastname: Hoegh-Guldberg
mesh_terms: D000818:Animals; D037421:Anthozoa / Q000201:enzymology / Q000235:genetics* / Q000528:radiation effects; D017209:Apoptosis / Q000528:radiation effects; D004249:DNA Damage; D004260:DNA Repair / Q000502:physiology*; D004255:Deoxyribodipyrimidine Photo-Lyase / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology; D007814:Larva / Q000201:enzymology / Q000235:genetics / Q000528:radiation effects; D012333:RNA, Messenger / Q000378:metabolism; D014466:Ultraviolet Rays
chemical_list: D012333:RNA, Messenger; D004255:Deoxyribodipyrimidine Photo-Lyase