Fluorescent chromosome banding in Chamaelirium hisauchianum (Melanthiaceae) with particular focus on the polycentricity

Abstract

Somatic chromosomes in three subspecies of Chamaelirium hisauchianum from Japan were examined by fluorescent banding methods using probes for AT- or GC-rich DNA. Evidence showed that there are two kinds of constitutive heterochromatin; one constitutes portions deemed as centromeres rich in AT base pairs, and the other is of segments (probably of NORs) rich in GC base pairs. Nuclei at interphase had numerous scattered small centromeres each often accompanying a small condensed pericentric chromatin mass. Chromosomes at prophase displayed an irregular beaded structure, of which the knobby portions contained centromeres. Chromosomes at metaphase had approximately two to five pairs of sister centromeres aligning on the lateral sides and often protruded in opposite (polar) directions. Sister chromatids at anaphase separated parallel, turning their centromeres toward spindle poles. Chromosomes at telophase were unevenly unraveled, showing a configuration similar to those at prophase. Centromeres appeared compacted almost through the mitotic cell cycle. Data suggested that the chromosomes of C. hisauchianum comprise plural subunits each containing a centromere and are polycentric. It is evident that they contrastively differ from the monocentric, single-unitary chromosomes of the North American congener C. luteum reported previously.