The protein kinases AtMAP3K epsilon 1 and BnMAP3K epsilon 1 are functionalhomologues of S. pombe cdc7p and may be involved in cell division

We identified an Arabidopsis thaliana gene, AtMAP3K epsilon1, and a Brassic a napus cDNA, BnMAP3K epsilon1, encoding functional protein serine/threonin e kinases closely related to cdc7p and Cdc15p from Schizosaccharomyces pomb e and Saccharomyces cerevisiae, respectively. This is the first report of c dc7-related genes in non-fungal eukaryotes; no such genes have as yet been identified in Metazoans. The B. napus protein is able to partially compleme nt a cdc7 loss of function mutation in S. pombe. RT-PCR and in situ hybridi sation revealed that the A. thaliana and B. napus genes are expressed in bo th the sporophytic and the gametophytic tissues of the respective plant spe cies and revealed further that expression is highest in dividing cells. Mor eover, AtMAP3K epsilon1 gene expression is cell cycle-regulated, with highe r expression in G2-M phases. Our results strongly suggest that the plant cd c7p-related protein kinases are involved in a signal transduction pathway s imilar to the SIN pathway, which positively regulates cytokinesis in S. pom be.