Putative subunits of the maize origin of replication recognition complex ZmORC1-ZmORC5

Xiahong Witmer, Raul Alvarez-Venegas, Philip San-Miguel, Olga Danilevskaya, Zoya Avramova

Research output: Contribution to journalReview articlepeer-review

20 Scopus citations


The finding in animal species of complexes homologous to the products of six Saccharomyces cerevisiae genes, origin of replication recognition complex (ORC), has suggested that ORC-related mechanisms have been conserved in all eukaryotes. In plants, however, the only cloned putative homologs of ORC subunits are the Arabidopsis ORC2 and the rice ORC1. Homologs of other subunits of plant origin have not been cloned and characterized. A striking observation was the absence from the Arabidopsis genome of an obvious candidate gene-homolog of ORC4. This fact raised compelling questions of whether plants, in general, and Arabidopsis, in particular, may have lost the ORC4 gene, whether ORC-homologous subunits function within a complex in plants, whether an ORC complex may form and function without an ORC4 subunit, whether a functional (but not sequence) protein homolog may have taken up the role of ORC4 in Arabidopsis, and whether lack of ORC4 is a plant feature, in general. Here, we report the first cloned and molecularly characterized five genes coding for the maize putative homologs of ORC subunits ZmORC1, ZmORC2, ZmORC3, ZmORC4 and ZmORC5. Their expression profiles in tissues with different cell-dividing activities are compatible with a role in DNA replication. Based on the potential of ORC-homologous maize proteins to bind each other in yeast, we propose a model for their possible assembly within a maize ORC. The isolation and molecular characterization of an ORC4-homologous gene from maize argues that, in its evolution, Arabidopsis may have lost the homologous ORC4 gene.

Original languageEnglish (US)
Pages (from-to)619-628
Number of pages10
JournalNucleic acids research
Issue number2
StatePublished - Jan 15 2003
Externally publishedYes

ASJC Scopus subject areas

  • Genetics


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