Studies on The Structure and Construction of Plant Chromosomes. The Molecular and Cellular Approaches.

本合作研究的目的是从分子水平和细胞水平探讨高等植物染色体结构变化与基因表达的关系。主要研究结果如下：1.分子水平的研究。(1)通过Ti质粒基因转移法转化向日葵细胞，在体内转录实验中证实了小麦组蛋白H3和H4基因转录的顺式和反式调控元件的存在。(2)花椰菜染色质的体内重组实验表明，DNA拓扑异构酶<II>参与了染色体的构建过程。(3)蚕豆核基因组中的两种高度重复的DNA序列被认为是异染色质的主要组成部分之一。(4)豌豆染色质的体外实验表明，钙离子对染色质的结构和模板活性有影响.细胞水平的研究。(1)间期染色体的形状和DNA复制方式的差异导致了拟南芥体细胞中期染色体的形态差异。延龄草属和百合属花粉母细胞减数分裂染色体也得到了类似的结果。(2)花粉粒细胞DNA甲基化与染色体结构的变化有关，如染色质的浓缩或分散.细胞器染色体的研究。(1)阐明了高等植物线粒体的染色体形成DNA-蛋白质复合体，而不是以游离DNA形式存在。(2)通过电镜观察，推测了花椰菜线粒体DNA的复制起点。

The object of the present co-operative research is to investigate the relationship between the gene expression and the structural changes of chromosomes in higher plants at the molecular and cellular levels. The results obtained here are as follows.1. Research at the molecular level.(1) The existence of the cis-and trnas-acting control elements for the transcription of wheat histone H3 and H4 genes was demonstrated in the in vivo transcription experiment with transformed sunflower cells by the Ti plasmid gene transfer method. (2) The in vivo reconstitution experiments with cauliflower chromatin showed that DNA topoisomerase <II> is involved in the process of the construction of chromosomes. (3) Two kinds of the highly repeated DNA sequences in the Vicia faba nuclear genome were supposed to be one of the major constituents of heterochromatin. (4) It was demonstrated in the in vitro experiments with isolated pea chromatin that calcium ions affect the structure and template activity of chromatin.2. Research at the cellular level.(1) The differences in the shape of chromosomes at the interphase and the DNA replication pattern resulted in the morphological differences of the metaphase chromosomes in the orchis somatic cells. Similar results were obtained with meiotic chromosomes in the pollen mother cells of Trillium and Lillium. (2) The DNA methylation was connected with the structural changes of chromosomes, such as the condensation or the dispersion of chromatin, in the pollen grain cells.3. Research of organella chromosomes.(1) It was clarified that the chromosomes of higher plant mitochondria form the DNA- protein complex but do not exist as free DNA. (2) The DNA replication origin of the cauliflower mitochondria DNA was estimated by the electron-microscopic observation of DNA.