title: Characterization of Arabidopsis photolyase enzymes and analysis of their role in protection from ultraviolet-B radiation.
abstract: DNA photolyases are enzymes which mediate the light-dependent repair (photoreactivation) of UV-induced damage products in DNA by direct reversal of base damage rather than via excision repair pathways. Arabidopsis thaliana contains two photolyases specific for photoreactivation of either cyclobutane pyrimidine dimers (CPDs) or pyrimidine (6-4)pyrimidones (6-4PPs), the two major UV-B-induced photoproducts in DNA. Reduced FADH and a reduced pterin were identified as cofactors of the native Arabidopsis CPD photolyase protein. This is the first report of the chromophore composition of any native class II CPD photolyase protein to our knowledge. CPD photolyase protein levels vary between tissues and with leaf age and are highest in flowers and leaves of 3-5-week-old Arabidopsis plants. White light or UV-B irradiation induces CPD photolyase expression in Arabidopsis tissues. This contrasts with the 6-4PP photolyase protein which is constitutively expressed and not regulated by either white or UV-B light. Arabidopsis CPD and 6-4PP photolyase enzymes can remove UV-B-induced photoproducts from DNA in planta even when plants are grown under enhanced levels of UV-B irradiation and at elevated temperatures although the rate of removal of CPDs is slower at high growth temperatures. These studies indicate that Arabidopsis possesses the photorepair capacity to respond effectively to increased UV-B-induced DNA damage under conditions predicted to be representative of increases in UV-B irradiation levels at the Earth's surface and global warming in the twenty-first century.
authors.affiliation: School of Biological Sciences, University of Manchester, Oxford Road, Manchester M13 9PT, UK. mqbsswmw@man.ac.uk
authors.forename: Wanda M
authors.initials: WM
authors.lastname: Waterworth
authors.forename: Qing
authors.initials: Q
authors.lastname: Jiang
authors.forename: Christopher E
authors.initials: CE
authors.lastname: West
authors.forename: M
authors.initials: M
authors.lastname: Nikaido
authors.forename: Clifford M
authors.initials: CM
authors.lastname: Bray
mesh_terms: D000222:Adaptation, Physiological; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000528:radiation effects; D004249:DNA Damage; D003624:Darkness; D004255:Deoxyribodipyrimidine Photo-Lyase / Q000302:isolation & purification / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D008027:Light; D018515:Plant Leaves / Q000201:enzymology / Q000235:genetics / Q000528:radiation effects; D018547:Plant Stems / Q000201:enzymology / Q000235:genetics / Q000528:radiation effects; D011740:Pyrimidine Dimers / Q000378:metabolism*; D013696:Temperature; D014466:Ultraviolet Rays
chemical_list: D011740:Pyrimidine Dimers; C098727:pyrimidine(6-4)pyrimidone photolyase; D004255:Deoxyribodipyrimidine Photo-Lyase