Abstract:
The Aurora B kinase, encoded by the AURORA 3 (AUR3) gene in Arabidopsis (Arabidopsis thaliana), is a key regulator of cell
division in all eukaryotes. Aurora B has at least two central functions during cell division; it is essential for the correct, i.e.
balanced, segregation of chromosomes in mitosis and meiosis by controlling kinetochore function, and it acts at the division
plane, where it is necessary to complete cytokinesis. To accomplish these two spatially distinct functions, Aurora B in animals is
guided to its sites of action by Borealin, inner centromere protein (INCENP), and Survivin, which, together with Aurora B, form
the chromosome passenger complex (CPC). However, besides Aurora homologs, only a candidate gene with restricted
homology to INCENP has been described in Arabidopsis, raising the question of whether a full complement of the CPC
exists in plants and how Aurora homologs are targeted subcellularly. Here, we have identified and functionally
characterized a Borealin homolog, BOREALIN RELATED (BORR), in Arabidopsis. Together with detailed localization studies
including the putative Arabidopsis INCENP homolog, these results support the existence of a CPC in plants.