ABSTRACT
We investigated the mechanism underlying this surveillance mechanism in plants, by characterizing the orthogolous SAC proteins BUBR1, BUB3, and MAD2 from Arabidopsis. We showed that the cell cycle-regulated BUBR1, BUB3.1, and MAD2 proteins interacted physically with each other. Furthermore, BUBR1 and MAD2 interacted specifi cally at chromocenters. Following SAC activation by global defects in spindle assembly, these three interacting partners localized to unattached kinetochores. In addition, in cases of “wait anaphase”, plant SAC proteins were associated with both kinetochores and kinetochore MTs. Unexpectedly, BUB3.1 was also found in the phragmoplast midline during the fi nal step of cell division in plants.
