| Cytoplasmic male sterility (CMS) and fertility restoration (Rf) gene system in high plants attract the interest of breeders mainly for facilitating the utilization of heterosis to produce vigorous F1 hybrids. It is well known that there are three genetically different types of CMS systems in rice, which were termed as Wild-abortive (WA), Chinsurah Boro-Taichong65 (BT) and Honglian (HL) systems. Wild-abortive CMS rice has been considered contribute great to the development of hybrid rice. But, it is still accounted for over 90% of the cultivated area of hybrid rice in China. Such an uniformity of cytoplasm will accumulate the latent risk in commercial production. Exploitation of Honglian cytoplasm to breed alternatively elite CMS lines and corresponding restorer lines will enrich the diversity of hybrid rice and will also do great contribution to the well-development of hybrid rice. To such an ends, the molecular and genetic mechanisms for CMS and fertility restoration of Honglian CMS system were performed in this paper. The results are shown below.I. The key role of mitochondria in the integration of apoptosis and oxidative stress in mammalian has been well documented. In plants, mitochondrion was suggested being implicated in cytoplasimc male sterility (CMS), programmed cell death (PCD), and oxidative stress. However, there is no evidence involved in the relationships among CMS, PCD and oxidative stress so far. In this study, we have demonstrated that the pollen abortion in Honglian CMS line of rice (Oryza saliva L.) displayed a PCD phenomenon characterized by the premature microspores on the basis of biochemical markers of apoptosis. Analysis of mitochondria revealed that during PCD process, the loss of the inner mitochondrial membrane potential, increase of reactive oxygen species, were accompanied by down-regulation of ROS scavenging enzymes inmitochondria. Our data suggest that the tissue-specific PCD in Honglian-CMS line of rice is mediated by chronic oxidative stress and finally resulted in the abortion of microspores. Plant mitochondria played a key role in the integration of CMS, PCD and oxidative stress.2. It is a tendency to exploit the newly developed biotechnology for developing of elite rice lines with specific characters in the breeding program. As the progress of the rice genomics, some newly developed genes or molecular markers connected to some a specific agronomic character were exploited to screen the valuable wild relatives of rice for the nicety and rapidity. The discovery of chimcric gene orfH79 related to Honglian CMS provides us the possibility to detect the distribution of Honglian cytoplasm in wild rice with AA genome. PCR and Southern blot analysis showed that in the 37 investigated accessions, eight were identified having the Honglian CMS related gene orfH79. Field experiment further demonstrated that the pollen grains of the sterile plants in F1 or BC1F1 derived from the crosses between wild rice and Honglian maintainer YuctaiB had the same abortive characteristic as that of Honglian CMS line. Sequence analysis showed that there were 13 nucleotide substitutions being detected in all the eight accessions and the sequence identity was among 98-100%, among of which, nine nucleotide substitutions altered the composition of the amino acid in the predicted protein.To elucidate the rearrangement of mitochondria! genome, the total DNA in the plants of w15(w20), the hybrid F1, sterile plants of BC1 and BC2 derived from crosses between wild rice w15(w20) and Yuctai B were extracted and digested by restriction endonuclease. RFLP analysis were carried out with eight mitochondrial DNA probes, and the result showed that a total of 54 bands were detected in the 24 compositions of restriction endonuclcases x probes. A total of 15 recombination events were detected in w15 and w20 series, among of which, 13 recombination events occurred in the descendenls derived from w15 , and the others occurred in that of w20.3. To understand the relationships among the fertility restoring loci for Ho...
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