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Three-dimensional structures of interphasic nucleous organizing regions in higher plants

高等植物间期核组织区的三维结构

基本信息

批准号：
07640884
负责人：
SATO Seiichi
金额：
$ 1.09万
依托单位：
Ehime University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

项目摘要

The structural organization of the nucleolus, especially the DNA-containing structure, was examined in Vicia faba root-tip cells exposed to hypoxia. Hypoxic conditions were attained by boiling distillled water and immediately cooling down to 23ﾟC.The nucleoli suffered stepwise structural alterations with exposure time as follows ; (1) nucleolar segregation, (2) nucleolar dispersion, (3) appearance of argyrophilic stands and (4) complete disappearance. Electron microscopy showed that the fibrillar centers (FCs) gradually develop with appearance of large particles (35 nm granules) inside and concomitantly with these phenomenon, chromatin and endomenbrane began to collapse. When immunogold labeling with an anti-DNA antibody was applied, the dense fibrillar component (DFC) was moderately labeled in cells of an actively growing root, whereas under hypoxia the label on the DFC gradually decreased with time and chromatin-like masses in the Fcs were most heavily labeled. This suggest that rDNA engaged in transcription retired from the DFC into the FCs under hypoxia.Thick and thin nucleolonema were seen in the nucleolus of Raphanus sativus. In meristematic cells, the two types of nucleoli, those with mainly thick nucleolonema and with mostly thin nucleolonema, were seen while the nucleoli with thin nucleolonema wes most frequently found in the differentiated cells. Silver staining was applied to thin sections of the specimen embedded in Spurrs resin. As the result, three types of nucleolonema segments were appreciated ; (1) stack of short fragments, (2) two rays of round-shape segments and (3) ring-shape segments. All these segments were arranged in 450 nm width. The appearance of these three types of nucleolonema segments is well elucidated by an idea that the nucleolonema filament coils up to form 450 nm thick nucleolonema. This coiling of the nucleolonema may reflect chromosome solenoid. This coil probably begin to collapse as cells differentiate.

本文研究了低氧条件下蚕豆根尖细胞核仁的结构组成，特别是含DNA的结构。通过煮沸去离子水并立即冷却至23 ℃来达到低温条件。核仁随暴露时间经历以下逐步结构变化：（1）核仁分离，（2）核仁分散，（3）嗜银性支架的出现和（4）完全消失。电镜观察发现，纤维中心（FC）逐渐发育，内部出现大颗粒（35 nm），同时染色质和内膜开始崩解。当应用免疫金标记与抗DNA抗体，致密的纤维状成分（DFC）是中度标记在细胞中的一个积极增长的根，而在缺氧的DFC上的标签逐渐减少，随着时间的推移和染色质样群众在FCs标记最重。这说明在低氧条件下，参与转录的rDNA从DFC中退入FC中。在分生组织细胞中，核仁有两种类型，即以粗核丝为主和以细核丝为主，而以细核丝为主的核仁在分化细胞中最常见。将银染色应用于包埋在Spurrs树脂中的标本的薄切片。结果表明，核丝节可分为三种类型：（1）短片段堆叠型，（2）两条圆形节和（3）环形节。所有这些片段以450 nm的宽度排列。这三种类型的核丝节的外观很好地阐明了一个想法，即核丝卷曲形成450 nm厚的核丝。核线体的这种卷曲可能反映了染色体螺线管。当细胞分化时，这个螺旋可能开始塌陷。