title: Diurnal change of cucumber CPD photolyase gene (CsPHR) expression and its physiological role in growth under UV-B irradiation.
abstract: Complementary DNA encoding a putative cyclobutane pyrimidine dimer (CPD)-specific DNA photolyase (CPD photolyase) was isolated from cucumber leaves. The deduced amino acid sequence of the cDNA exhibited high similarity to that of the Arabidopsis CPD photolyase. Transformation with the cDNA restored the impaired photorepair activity of an Escherichia coli mutant, indicating that this cDNA encodes a functional cucumber CPD photolyase (CsPHR). The level of CsPHR transcripts estimated by quantitative RT-PCR as well as the CPD photorepair activity in the cucumber first leaves showed diurnal changes, peaking at 09 : 00 and 12 : 00, respectively. Supplemental UV-B irradiation in the middle of the light period had little effect on the growth of the first leaves, while the supplemental irradiation in the early morning or late afternoon strongly retarded the leaf growth. These results suggest that the diurnal change in CPD photorepair activity, which is presumably regulated by the transcript level of CsPHR, may play an important role in minimizing the growth inhibition due to UV-B irradiation.
authors.affiliation: Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, 113-0033, Japan. GD6S-TKHS@asahi-net.or.jp
authors.forename: Shinya
authors.initials: S
authors.lastname: Takahashi
authors.forename: Nobuyoshi
authors.initials: N
authors.lastname: Nakajima
authors.forename: Hikaru
authors.initials: H
authors.lastname: Saji
authors.forename: Noriaki
authors.initials: N
authors.lastname: Kondo
mesh_terms: D000595:Amino Acid Sequence; D002940:Circadian Rhythm / Q000502:physiology*; D018553:Cucumis sativus / Q000235:genetics* / Q000254:growth & development / Q000528:radiation effects; D004260:DNA Repair; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification; D004255:Deoxyribodipyrimidine Photo-Lyase / Q000235:genetics* / Q000502:physiology; D004307:Dose-Response Relationship, Radiation; D004926:Escherichia coli / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic / Q000528:radiation effects; D018506:Gene Expression Regulation, Plant / Q000528:radiation effects; D005816:Genetic Complementation Test; D008027:Light; D008969:Molecular Sequence Data; D009154:Mutation; D018515:Plant Leaves / Q000235:genetics / Q000254:growth & development / Q000528:radiation effects; D010940:Plant Proteins / Q000235:genetics* / Q000502:physiology; D011740:Pyrimidine Dimers / Q000378:metabolism; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D014466:Ultraviolet Rays
chemical_list: D018076:DNA, Complementary; D010940:Plant Proteins; D011740:Pyrimidine Dimers; D004255:Deoxyribodipyrimidine Photo-Lyase