Abstract
The Origin Recognition Complex (ORC) is essential for initiation of DNA replication in eukaryotes. ORC1 protein is the largest subunit of ORC. In the Arabidopsisgenome, two ORC1 homologues, AtORC1a and AtORC1b, exist. However those functions are not characterized.In this study, we analyzed the function of AtORC1a and AtORC1b in vivo. Both genes complemented yeast ORC1 function in budding yeast cells. These proteins were localized in nuclei. In AtORC1a homozygous mutants, the root elongation in the early developmental stage was retarded both under the low temperature condition and on the antibiotic containing medium at RT. Cell cycle progressions of root tip cells of this mutant are arrested in S phase. On the other hand, AtORC1b homozygous mutants were lethal. Expression of AtORC1b gene was detected in root tips, root primordia and shoot apices. Function of AtORC1 genes in DNA replication and plant development will be discussed.
