Physical Map of FISH 5S rDNA and (AG(3)T(3))(3) Signals Displays Chimonanthus campanulatus R.H. Chang & C.S. Ding Chromosomes, Reproduces its Metaphase Dynamics and Distinguishes Its Chromosomes

Chimonanthus campanulatus R.H. Chang & C.S. Ding is a good horticultural tree because of its beautiful yellow flowers and evergreen leaves. In this study, fluorescence in situ hybridization (FISH) was used to analyse mitotic metaphase chromosomes of Ch. campanulatus with 5S rDNA and (AG(3)T(3))(3) oligonucleotides. Twenty-two small chromosomes were observed. Weak 5S rDNA signals were observed only in proximal regions of two chromosomes, which were adjacent to the (AG(3)T(3))(3) proximal signals. Weak (AG(3)T(3))(3) signals were observed on both chromosome ends, which enabled accurate chromosome counts. A pair of satellite bodies was observed. (AG(3)T(3))(3) signals displayed quite high diversity, changing in intensity from weak to very strong as follows: far away from the chromosome ends (satellites), ends, subtelomeric regions, and proximal regions. Ten high-quality spreads revealed metaphase dynamics from the beginning to the end and the transition to anaphase. Chromosomes gradually grew larger and thicker into linked chromatids, which grew more significantly in width than in length. Based on the combination of 5S rDNA and (AG(3)T(3))(3) signal patterns, ten chromosomes were exclusively distinguished, and the remaining twelve chromosomes were divided into two distinct groups. Our physical map, which can reproduce dynamic metaphase progression and distinguish chromosomes, will powerfully guide cytogenetic research on Chimonanthus and other trees.