MINUS END-DIRECTED KINESIN-LIKE MOTOR PROTEIN, KCBP, LOCALIZES TO ANAPHASE SPINDLE POLES IN HAEMANTHUS ENDOSPERM

Microtubule-based motor proteins assemble and reorganize acentrosomal mitotic and meiotic spindles in animal cells. The functions of motor p roteins in acentrosomal plant spindles are unknown. The cellulosic cel l wall and relative small size of most plant cells precludes accurate detection of the spatial distribution of motors in mitosis. Large cell size and absence of a cellulosic cell wall in Haemanthus endosperm ma ke these cells ideally suited for studies of the spatial distribution of motor proteins during cell division. :Immunolocalization of a kines in-like calmodulin-binding protein (KCBP) in Haemanthus endosperm reve aled its mitotic distribution. KCBP appears first in association with the prophase spindle. Highly concentrated within the cores of individu al kinetochore fibers, KCBP decorates microtubules of kinetochore-fibe rs through metaphase. By mid-anaphase (when a barrel-shaped spindle be comes convergent), the protein redistributes and accumulates at the sp indle polar regions. In telophase, KCBP relocates toward the phragmopl ast and cell plate. These data suggest a role for KCBP in anaphase spi ndle microtubule convergence, which assures coherence of kinetochore-f ibers within each sister chromosome group. Increasing coherence of kin etochore-fibers prevents splitting within each sister chromosome group and formation of multinucleated cells. Cell Motil. Cytoskeleton 41:27 1-280, 1998. (C) 1998 Wiley-Liss,Inc.