Behavior of the Differentially Stained Kinetochores During the Mitotic Cell Cycle in Some Polygonatum Species (Liliaceae)

Abstract

Chromosomes in the root-tip cells in four species and one variety belonging to the genus Polygonatum (Liliaceae) were treated according to the modified C-banding technique. As results, both the centromeric regions and the secondary constrictions of the satellite chromosomes in each species were found specifically deeply stained. In P. odoratum var. pluriflorum, besides these chromosomal regions, distal regions of several chromosomal arms were also stained deeply.
The stained portion in the centromeric region of the chromosome is spherical in shape and has a diameter of 0.2-0.3μ, and is always seen at the apex of the chromosome flexure migrating toward the spindle pole at mitotic anaphase. The appearance and the behavior of this centromeric spherule were found quite compatible with some of the known characteristics of kinetochores. These stained kinetochores could also be seen in the interphase nuclei. They localize in a cluster at one side of the nucleus. The observations on the appearance and behavior of these stained kinetochores allowed us to suppose that chromosomes in interphase, prophase and late telophase are strongly polarized, and arranged keeping their anaphase-telophase orientation. As the kinetochores during these periods could always be seen in the periphery of the nucleus, adjacent to the nuclear membrane, they were considered to be attached to the inner layer of the nuclear membrane, and to act as the anchore sites to link the chromosomes. Thus the role of the kinetochores during these periods was emphasized.
During interphase, initial single kinetochores were found to replicate and form the doubled ones. But these doubled kinetochores do not divide until the earliest prophase. Some of the doubled kinetochores seemed to fuse two by two to form larger spherules during the interphase.
As the kinetochores could be stained after C-banding treatment, they were supposed, accordingly, to be constitutive heterochromatic regions in the present materials.