title: Characterization of the origin recognition complex (ORC) from a higher plant, rice (Oryza sativa L.).
abstract: The origin recognition complex (ORC) protein plays a critical role in DNA replication through binding to sites (origins) where replication commences. The protein is composed of six subunits (ORC1 to 6) in animals and yeasts. Our knowledge of the ORC protein in plants is, however, much less complete. We have performed cDNA cloning and characterization of ORC subunits in rice (Oryza sativa L. cv. Nipponbare) in order to facilitate study of plant DNA replication mechanisms. Our previous report provided a description of a gene, ORC1 (OsORC1), that encodes one of the protein subunits. The present report extends this initial analysis to include the genes that encode four other rice ORC subunits, OsORC2, 3, 4 and 5. Northern hybridization analyses demonstrated the presence of abundant transcripts for all OsORC subunits in shoot apical meristems (SAM) and cultured cells, but not in mature leaves. Interestingly, only OsORC5 showed high levels of expression in organs in which cell proliferation is not active, such as flag leaves, the ears and the non-tip roots. The pattern of expression of OsORC2 also differed from other OsORC subunits. When cell proliferation was temporarily halted for 6-10 days by removal of sucrose from the growth medium, expression of OsORC1, OsORC3, OsORC4 and OsORC5 was substantially reduced. However, the level of expression of OsORC2 remained constant. We suggest from these results that expression of OsORC1, 3, 4 and 5 are correlated with cell proliferation, but the expression of OsORC2 is not.
authors.affiliation: Department of Applied Biological Science, Faculty of Science and Technology, Science University of Tokyo, 2641 Yamazaki, Noda-shi, Chiba-ken 278-8510, Japan.
authors.forename: Yoko
authors.initials: Y
authors.lastname: Mori
authors.forename: Taichi
authors.initials: T
authors.lastname: Yamamoto
authors.forename: Norihiro
authors.initials: N
authors.lastname: Sakaguchi
authors.forename: Toyotaka
authors.initials: T
authors.lastname: Ishibashi
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Furukawa
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Kadota
authors.forename: Kazuyuki
authors.initials: K
authors.lastname: Kuchitsu
authors.forename: Junji
authors.initials: J
authors.lastname: Hashimoto
authors.forename: Seisuke
authors.initials: S
authors.lastname: Kimura
authors.forename: Kengo
authors.initials: K
authors.lastname: Sakaguchi
mesh_terms: D019470:Biolistics; D015152:Blotting, Northern; D002467:Cell Nucleus / Q000378:metabolism; D049109:Cell Proliferation; D002478:Cells, Cultured; D002874:Chromosome Mapping; D032461:Chromosomes, Plant / Q000235:genetics; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics*; D005091:Exons; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant / Q000235:genetics; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D007438:Introns; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D051738:Origin Recognition Complex; D012275:Oryza / Q000235:genetics*; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics*; D021122:Protein Subunits / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D017422:Sequence Analysis, DNA; D013395:Sucrose / Q000494:pharmacology
chemical_list: D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D051738:Origin Recognition Complex; D010940:Plant Proteins; D021122:Protein Subunits; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; D013395:Sucrose