Characterization of Plant Homologues of Five Subunits of Origin Recognition Complex (ORC)

Abstract

Origin Recognition Complex (ORC) is known to be a protein complex composed of six subunit proteins in animals and yeasts, and the function is to recognize a DNA replication origin. To study plant DNA replication mechanism, we performed cDNA cloning and characterization of OsORC subunits in rice (Oryza sativa L. cv. Nipponbare). The results of northern hybridization analysis suggested that, all OsORC subunit transcripts were strongly expressed in the shoot apical meristems (SAM) and the culutured cells, but not detected in the mature leaves. Similarly, although the expression levels of OsORC1, 3, 4 and 5 subunits were decreased in the growth halted cells and returned to the previous levels in the re-growthed cells, the expression of OsORC2 is ubiquitous. These results suggested that OsORC2 may have different functions from other ORC subunit.