Study on mitotic and meiotic homologous recombination in plant and cultured cells of rice

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1.Analysis of occurrence of MCO in cultured cell of rice : Calli were induced from F_1 seed (Wxwx) of glutinous rice (wxwx) as a seed parent and non-glutious rice(WxWx) as a pollen parent. After regeneration of rice plamts, it was found a dominant homologous plant(WxWx) which might be segregated by the MCO.2.Analysis of structure and expression pattern of RiLIM15 in rice : In order to clarify the relationships between occurrence of MCO and expression of RiLIM15 gene in cultured cells and panicles investigated on the aspects of structure and expression of RiLIM15. Two RiLIM15 homologous RiLIM15A and RiLIM15B were isolated. In exon region, the DNA sequences for two genes were highly homologous but not intron regions. The amino acid sequences these two genes were highly homologous, sugggesting that they may be nearly equivalent in function. Analysis of cDNA sequences that eight patterns of deletions of DNA sequences in RiLIM15 cDNA clones derived from both meiotic and cultured cells. They may be resulted from alternative splicing. The putative mRNA with these deletion may translate different functions of proteins.3.Analysis of RAD51 in rice : RT-PCR was performed using total RNA extracted from the cultured cells, young meiotic panicles, mature leaves and X-ray treated seedlings. Expression of the RAD51 gene was found to occur in cultured cells, young meiotic panicles and X-ray treated seedlings, but not mature leaves. The gene possibly participates in DNA repariring of MCO.4.Application to substantial plant breeding : In nine generation of progenies regenerated from calli of cv.Akihikari it was observed that a line is 3-4 early heading date and almost the same number of panicle as the parent cultivar and significantly higher thousand kernel weight than the parent cultivar.