The Arabidopsis MCM2 gene is essential to embryo development and its over-expression alters root meristem function

· MCM proteins are sub-units of the pre-replication complex that probably function as DNA helicases during the S-phase of the cell cycle. We investigated the function of AtMCM2 in Arabidopsis. · To gain insight into the function of AtMCM2, we combined loss and gain of function approaches. To this end, we analysed two null alleles of AtMCM2, and generated transgenic plants expressing AtMCM2 downstream of the constitutive 35S promoter. · Disruption of AtMCM2 is lethal at a very early stage of embryogenesis, while its over-expression results in reduced growth and inhibition of endoreduplication. In addition, over-expression of AtMCM2 induces the formation of additional initials in the columella root cap. In the plt1,2 mutant, defective for root apical meristem maintenance, over-expression of AtMCM2 induces lateral root initiation close to the root tip, a phenotype never reported neither in the wild-type nor in plt1,2 mutants, even when cell cycle regulators such as AtCYCD3;1 were over-expressed. · Taken together, our results provide evidence for the involvement of AtMCM2 in DNA replication and suggest it plays a crucial role in root meristem function.