Spindle assembly checkpoint protein dynamics reveal conserved and unsuspected roles in plant cell division.
BACKGROUND
In eukaryotes, the spindle assembly checkpoint (SAC) ensures that chromosomes undergoing mitosis do not segregate until they are properly attached to the microtubules of the spindle.


RESULTS
We investigated the mechanism underlying this surveillance mechanism in plants, by characterising 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 specifically at chromocenters. Following SAC activation by global defects in spindle assembly, these three interacting partners localised to unattached kinetochores. In addition, in cases of 'wait anaphase', plant SAC proteins were associated with both kinetochores and kinetochore microtubules. Unexpectedly, BUB3.1 was also found in the phragmoplast midline during the final step of cell division in plants.


CONCLUSIONS
We conclude that plant BUBR1, BUB3.1 and MAD2 proteins may have the SAC protein functions conserved from yeast to humans. The association of BUB3.1 with both unattached kinetochore and phragmoplast suggests that in plant, BUB3.1 may have other roles beyond the spindle assembly checkpoint itself. Finally, this study of the SAC dynamics pinpoints uncharacterised roles of this surveillance mechanism in plant cell division.
Caillaud
Marie-Cécile
MC
Institut National de la Recherche Agronomique, Unité Mixte de Recherche 1301, Sophia-Antipolis, France.
Paganelli
Laetitia
L
Lecomte
Philippe
P
Deslandes
Laurent
L
Quentin
Michaël
M
Pecrix
Yann
Y
Le Bris
Manuel
M
Marfaing
Nicolas
N
Abad
Pierre
P
Favery
Bruno
B
D017360:Arabidopsis / Q000166:cytology* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002455:Cell Division; D032461:Chromosomes, Plant; D003001:Cloning, Molecular; D011401:Promoter Regions, Genetic; D008941:Spindle Apparatus; D020798:Two-Hybrid System Techniques
D029681:Arabidopsis Proteins