2021 Volume 24 Issue 1-2 Pages 29-37
Somatic chromosomes of Chamaelirium japonicum (2n=24) and C. koidzumianum (2n=24) from Japan were investigated by a fluorescent banding method using probes for AT- or GC-rich DNA. Data showed that there are two kinds of constitutive heterochromatin; one is rich in AT base pairs, constituting segments deemed as centromeres, and the other is rich in GC base pairs, constituting segments probably of NORs. The said centromeres were located on lateral sides of chromosomes at metaphase, varying in size from being almost invisible to ca. 0.3 μm in diameter. Discernibly distinct centromeres per nucleus counted ca. 12 on average in C. japonicum and ca. 25 in C. koidzumianum. Interphase chromosomes formed numerous small heterochromatic segments (HSs) that exceeded the somatic chromosome number ca. 3 times in C. japonicum and 4.3 times in C. koidzumianum. Each of the HSs contained a centromere, as long as the latter was discernible. It was suggested that every such HS contains a centromere, irrespective of the size and visibility of the latter, and that plural such segments organize a chromosome. The process of chromosomal diversification, especially of centromere organization, in Chamaelirium was inferred from a phylogenetic tree built from analyses of phenotypic characters.
