Globular and fibrous structure in barley chromosomes revealed by high-resolution scanning electron microscopy.
Barley chromosomes were prepared for high-resolution scanning electron microscopy using a combination of enzyme maceration, treatment in acetic acid and osmium impregnation using thiocarbohydrazide. Using this technique, the three-dimensional ultrastructure of interphase nuclei and mitotic chromosomes was examined. In Interphase, different levels of chromatin condensation were observed, consisting of fibrils 10 nm in diameter, 20- to 40-nm fibres and a higher order complex. In prophase, globular and strand-like structures composed of 20- to 40-nm fibres were dominant. As the cells progressed through the cell cycle and the chromatin condensed, globular and strand-like structures (chromomeres) were coiled and packed to form chromosomes. Chromomeres were observed as globular protuberances on the surface of metaphase chromosomes. These findings indicate that the chromomere is a fundamental substructure of the higher order architecture of the chromosome. In the centromeric region, there were no globular protuberances, but 20- to 40-nm fibres were folded compactly to form a higher level organization surrounding the chromosomal axia.
Iwano
M
M
Graduate School of Biological Sciences, Nara Institute of Science and Technology, Japan. m-iwano@bs.aist-nara.ac.jp
Fukui
K
K
Takaichi
S
S
Isogai
A
A
D002843:Chromatin / Q000648:ultrastructure; D002875:Chromosomes / Q000648:ultrastructure*; D001467:Hordeum / Q000235:genetics*; D007399:Interphase / Q000235:genetics; D008855:Microscopy, Electron, Scanning; D008938:Mitosis / Q000235:genetics; D013048:Specimen Handling / Q000379:methods
D002843:Chromatin