XVI International Botanical Congess

MCM (mini-chromosome maintenance) genes 2-7 are essential for origin activation and thus for initiation of DNA replication in eukaryotes. We are studying MCM genes in relation to DNA replication in the cell cycle. We have isolated partial-length MCM3 cDNAs from pea, Arabidopsis and tobacco. The 2.2kb clone from pea shows, at the amino acid level, 72% and 51% identity to maize and human MCM3 respectively. This clone recognises a 2.9kb mRNA in northern blots. The mRNA is detectable only in regions of the plant containing dividing cells. The cDNAs from Arabidopsis and tobacco show very close sequence homology to that from pea. We are investigating the expression of MCM3 in relation to cell cycle progression in aphidicolin-synchronised and non-synchronised tobacco BY2 cells. The results of these experiments will be reported.