Comparison of Surface Structures between Extended and Condensed Stages of Barley Chromosomes Revealed with Atomic Force Microscopy

抄録

Chromosomes are super-molecules consisting of DNA, histone and chromatin proteins, which specifically appear within a cell at the cell division. We analyzed barley chromosomes by atomic force microscopy (AFM) to elucidate its structural basis. Mitotic chromosomes were taken from root tips of barley (Hordeum vulgare L., cv. Minorimugi) using the EMA (enzymatic maceration and air-drying) method after synchronization of cell cycle. Both the air-dried or critical point dried specimens were observed in air by a dynamic force mode. This observation technique enables to obtain three-dimensional image data on the surface structure of barley chromosomes at high resolution without any metal coating. The details of the higher order chromosomal structure such as chromatin fibers were clarified with the biological significance. Acidic treatment (e.g., acetic acid treatment) for removing proteins was useful to obtain clear images of basic chromosomal structure. Thus, it is concluded that the AFM has a great potential for investigation of molecular structures of chromosomes.