MOLECULAR BASIS OF INTERORGANELLAR TRANSLOCATION IN WHEAT

本研究旨在探讨细胞器基因组，即叶绿体和线粒体之间的遗传通量。对小麦叶绿体基因向线粒体DNA的胞间易位进行了系统的追踪。通过适当的限制性内切酶或PCR扩增，构建了70个叶绿体基因的55个探针，其中包括所有蛋白质编码基因和rRNA基因。将这些探针与14个cosmid克隆杂交，这些克隆覆盖了小麦线粒体DNA主拷贝的整个部分。南方杂交分析表明，包含20个基因的12个探针对mtDNA克隆给出了阳性信号，表明这些基因易位。与水稻和玉米等其他禾本科植物相比，易位片段相对较小（0.3 ~ 3.0kbp）。据估计，这些位置共享14.6% （19.7kbp/135kbp）的cpDNA和4.6% （19.7kbp/430kbp）的线粒体主环DNA。易位叶绿体基因的总长度不足以解释被子植物线粒体基因组的巨大大小。易位基因在叶绿体DNA上的位置没有偏倚。在小麦mtDNA主环的物理图谱上定位了易位的叶绿体基因。大多数易位基因分散在小麦线粒体主环中，但也有一些基因聚集在易位相关热点的特定区域。小麦叶绿体基因在线粒体dna中的易位方式与水稻和玉米有很大不同，显示了线粒体基因组的可塑性。

The present study is aimed to investigate the genetic flux between organellar genomes, namely chloroplast and mitochondria. Interorganellar translocation of chloroplast genes into the mitochondrial DNA was systematically traced in wheat. Fifty-five probes responsible for 70 chloroplast genes, in which all protein-coding genes and rRNA genes are included, were constructged by digestion with the appropriate restriction endonucleases or PCR amplification. These probes were hybridized to the 14 cosmid clones which cover the entire part of a master copy of wheat mitochondria DNA.Southern hybridization analysis showed that twelve probes containing 20 genes gave positive signals to the mtDNA clones, showing the translocations of these genese. Translocated segments were relatively small (0.3kbp to 3.0kbp) in comparison to other grasses such as rice and maize. These positions are estimated to share 14.6% (19.7kbp/135kbp) of cpDNA and 4.6% (19.7kbp/430kbp) of mitochondrial master circle DNA.The total length of the translocated chloroplast genes is not enough to explain the enormous size of angiosperm mitochondrial genome. The positions of tranlocated genes on the chloroplast DNA were not biased. Translocated chloroplast genes were mapped on the physical map of a master circle of wheat mtDNA.Most tranlocated genes were dispersed throughout the wheat mitochondrial master circle, but some genes were clustered in the specific region consisting of hot spot related to translocations . The translocation modes of chloroplast genes into the wheat mtDNA greatly differed from those of rice and maize, showing the plasticity of mitochondrial genome.