Masa-Aki Yamada
National Institute of Genetics
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Chromosoma | 1994
Hirohisa Hirai; Masa-Toshi Yamamoto; Keiji Ogura; Yoko Satta; Masa-Aki Yamada; Robert W. Taylor; Hirotami T. Imai
AbstractChromosomal localization of rDNA in samples of five taxa of the Myrmecia pilosula species complex (Hymeoptera: Formicidae: Myrmeciinae) with 2n=3 (M. croslandi), 8 (M. imaii), 10 (M. banksi), 18 (M. haskinsorum), and 27 (M. pilosula) was carried out by fluorescence in situ hybridization (FISH) using cloned M. croslandi rDNA (pMc.r2) including the coding region for 28S rRNA. Results show that (1) the 28S rDNA in the genome of these ants is repetitive and is localized in pericentromeric C-bands, (2) the number of chromosomes carrying rDNA is two in M. croslandi, M. imaii and M. banksi, six in M. haskinsorum and ten in M. pilosula, and (3) only one or two clusters of rRNA genes generate nucleoli in each species. We suggest that the rDNA in the ancestral stock of the M. pilosula complex was localized originally in a pericentromeric C-band, and multiplied by chance with time during saltatory increases in C-banding following episodes of centric fission. Most rDNA multiplied on various chromosomes seems to be inactivated and eliminated from the genome, together with C-bands, by
Genetics Research | 1992
Yoshio Sano; Mitsugu Eiguchi; Hiro-Yuki Hirano; Masa-Aki Yamada
Genetics | 1971
Saburo Nawa; Bungo Sakaguchi; Masa-Aki Yamada; Mitsuo Tsujita
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The Japanese Journal of Genetics | 1992
Hirotami T. Imai; Hirohisa Hirai; Yoko Satta; Toshihiko Shiroishi; Masa-Aki Yamada; Robert W. Taylor
The Japanese Journal of Genetics | 1975
Saburo Nawa; Masa-Aki Yamada; Yasuo Ohta
-inversion or centric fusion, with the remnant rDNAs dispersed in the genome by centric fission and
The Japanese Journal of Genetics | 1982
Masa-Aki Yamada; Saburo Nawa
The Japanese Journal of Genetics | 1987
Saburo Nawa; Yoshio Sano; Masa-Aki Yamada; Taro Fujii
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The Japanese Journal of Genetics | 1985
Masa-Aki Yamada; Takao Koana
The Japanese Journal of Genetics | 1977
Masa-Aki Yamada
-inversion.
The Japanese Journal of Genetics | 1978
Saburo Nawa; Masa-Aki Yamada; Mitsuo Tsujita
The present study was carried out to examine the genetic mechanism responsible for reversions to fertile phenotype detected in cytoplasmic male-sterile plants of rice. The cms-bo cytoplasm of Chinsurah boro II gave rise to male-sterility in plants without a gametophytic restorer gene (/?/i). Taichung 65 (T65A) was known to be the maintainer which carries no restorer; however, Taichung 65 preserved in our laboratory (T65B) showed partial fertility (about 8 % seed set) when crossed with the male-sterile plants. Unexpectedly, the seed fertility gradually increased with repeated selfings and almost fully fertile plants were obtained in the F6 generation. The cytoplasmic substitution lines revealed that reversions to fertile phenotype resulted from mutational events at the nuclear level. The genetic experiments indicated that the partial fertility observed in the F1 hybrid was controlled by a dominant gene, Ifrv which was carried by T65B. The results obtained suggested that Ifr1 itself was associated with instability of fertility restoration in the presence of cms-bo cytoplasm since partially fertile plants carrying Ifrl always showed a tendency for gradual increase in fertility in the later generations. The results are also discussed in relation to a rapid genetic change through intensified gametic selection combined with instability.
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Commonwealth Scientific and Industrial Research Organisation
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