Physical Map of FISH 5S rDNA and (AG3T3)3 Signals Displays Chimonanthus campanulatus R.H. Chang & C.S. Ding Chromosomes, Reproduces its Metaphase Dynamics and Distinguishes Its Chromosomes.

Xiaomei Luo,Jingyuan Chen

doi:10.3390/genes10110904

Abstract

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 (AG3T3)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 (AG3T3)3 proximal signals. Weak (AG3T3)3 signals were observed on both chromosome ends, which enabled accurate chromosome counts. A pair of satellite bodies was observed. (AG3T3)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 (AG3T3)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.

Highlights

Fragrant species of Chimonanthus L. (Calycanthaceae) that are endemic to China and on The PlantList include six accepted taxa
Ten high-quality spreads of mitotic metaphase chromosomes of Ch. campanulatus after fluorescence in situ hybridization (FISH) are illustrated in Figure 1, Figure 2, Figure 3, and Figure 4, which exhibited dynamic metaphase progression from the preliminary stage to the final metaphase and confirmed the repeatability and stability of our FISH results
Chromosomes of each spread were aligned by their length from longest to shortest and their signal patterns

Summary

Introduction

Fragrant species of Chimonanthus L. (Calycanthaceae) that are endemic to China and on The PlantList include six accepted taxa. (Calycanthaceae) that are endemic to China and on The Plant. Chimonanthus campanulatus R.H. Chang & C.S. Ding was established as a new species by Chang and Ding [1]. The Chimonanthus chromosome number (2n = 22) was first reported by Sugiura [2]. Ch. campanulatus has a 2n = 2x = 22 = 20 m (2SAT) + 2 sm karyotype [3]. The other five species, namely, Chimonanthus grammatus M.C. Liu, Chimonanthus nitens Oliv., Chimonanthus nitens var. Salicifolius (S.Y. Hu) H.D. Zhang, Chimonanthus praecox (L.) Link, and Chimonanthus zhejiangensis

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Discussion

Conclusion