MOLECULAR BASIS OF INTERORGANELLAR TRANSLOCATION IN WHEAT

点击翻译按钮获取中文摘要

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.