The Japanese Journal of Genetics

ARTICLES

Action site of the lethal A^y gene in the mouse embryo

Yukio SAIJOH, Takuji TAKEUCHI

1992 Volume 67 Issue 5 Pages 357-370
Published: 1992
Released on J-STAGE: October 19, 2005

DOIhttps://doi.org/10.1266/jjg.67.357

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We investigated the lethal effect of A^y gene in embryos at the preimplantation stage in vitro. First, the development until the blastocyst stage and the division of individual cells from 8-cell stage embryos were examined. No difference in development was detected between embryos from the experimental cross (A^y/a × A^y /a) and those from the control cross (a/a × a/a). Therefore, it seems that the abnormality of the A ^y/A^y embryo does not appear until blastocyst formation in vitro. We subsequently examined the hatching from zona pellucida of the blastocysts. The hatching ratio of the embryos from the experimental cross was significantly lower than that of the control crosses (A^y/a × a/a, a/a × a/a: p<0.05). Our observation indicates that deficiency of the A ^y/A^y embryo can be detected in vitro at hatching. In order to elucidate the mechanism of the gene action of the A^y, we attempted to rescue the lethal embryos from decreased hatching ratio in vitro. When dbcAMP at the concentration of 1 mM was added to the culture medium, the hatching ratio of blastocysts from the experimental cross increased until the level of those from the control crosses. Since this result indicates that the cAMP content in A^y homozygote seemed to be lower than those in a/a and A^y /a, the cAMP content in individual blastocyst was quantified. It is found that A^y homozygosity was associated with lower level of cAMP. When adenylate cyclase was activated by forskolin and cholera toxin, the hatching,ratio was increased. These results seem to suggest that A^y homozygote embryos posses a defect in signal transduction system mediated by adenylate cyclase during hatching.

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Distribution of the necrosis and chlorosis genes in two wild tetraploid wheats, Triticum dicoccoides and T. araraticum

Naoki MORI, Koichiro TSUNEWAKI

1992 Volume 67 Issue 5 Pages 371-380
Published: 1992
Released on J-STAGE: October 19, 2005

DOIhttps://doi.org/10.1266/jjg.67.371

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Distributions of the Ne1 and Ne2 alleles for type 1 hybrid necrosis, and Ch1 allele for type 1 hybrid chlorosis in two wild tetraploid wheats, Triticum dicoccoides (wild emmer wheat) and T. araraticum (wild timopheevi wheat), have been investigated by crossing the collections of these species from their entire distribution areas with their appropriate testers. The frequencies of the Ne1 and Ch1 alleles were 53% and 13%, respectively, in T. dicoccoides; whereas they were 69% and 0% in T. araraticum. The Ne2 allele was not found in both species. The Ne1 allele of T. dicoccoides was mainly Ne1^m, while that of T. araraticum was mainly Ne1^w. The frequency of the Ch1 allele differed significantly between the two species. These facts indicate that the emmer and timopheevi groups of tetraploid wheat had been differentiated genetically before their domestication. On the frequencies of the Ne1 and Ch1 alleles, Israeli T. dicoccoides revealed high genetic homogeneity within local populations. While there was extreme variability among these populations, they showed no geographical inclination of their frequencies. These alleles are assumed to be neutral for selection and have been randomly fixed in most populations. A limited numbers of Sitopsis accessions of the genus Aegilops were tested for the two alleles, Ne1 and Ne2. None of them carried these alleles. Thus, the origin of the Ne1 alleles found in tetraploid wheats could not be traced back to any Sitopsis species.

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Differential staining and in situ hybridization of nucleolar organizers and centromeres in Cycas revoluta chromosomes

Masahiro HIZUME, Fumio ISHIDA, Katsuhiko KONDO

1992 Volume 67 Issue 5 Pages 381-387
Published: 1992
Released on J-STAGE: October 19, 2005

DOIhttps://doi.org/10.1266/jjg.67.381

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Nucleolar organizers (NORs) and centromeres in the somatic metaphase chromosomes (2n = 22) of Cycas revoluta Thunb. were differentially stained by silver staining and Cd-staining. Silver deposits (Ag-NORs) were located at the terminal end of the long arm of four submetacentric chromosomes and nine telocentric chromosomes. The maximum number of nucleoli per nucleus was 13. In situ hybridization with biotin-labeled rDNA revealed that rRNA genes were located at the terminal ends of four submetacentric chromosomes and all 12 telocentric chromosomes. Most of the signals of rDNA coincided to Ag-NORs. Differential staining with the DNA base specific fluorochromes indicated that the NORs were GC-rich and the centromeres were AT-rich. The proximal and terminal regions of the telocentric chromosomes were GC-rich. A few interstitial GC- and AT-rich bands were observed in some chromosomes.

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Multiple locations of the rRNA genes in chromosomes of pines, Pinus densiflora and P. thunbergii

Masahiro HIZUME, Fumio ISHIDA, Minoru MURATA

1992 Volume 67 Issue 5 Pages 389-396
Published: 1992
Released on J-STAGE: October 19, 2005

DOIhttps://doi.org/10.1266/jjg.67.389

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The ribosomal RNA (rRNA) genes were mapped on somatic chromosomes of Japanese red pine (Pinus densiflora) and Japanese black pine (P. thunbergii) by in situ hybridization using biotin-labeled 18S-25S rDNA. Cytochemical detection of the hybridized probe showed many signals in the interphase nuclei and, prophase and metaphase chromosomes in both species. In the metaphase complement of P. densiflora, the signals appeared singly at the interstitial region of seven pairs of the chromosomes. In P. thunbergii, ten strong and two weak signals appeared at the interstitial region of six pairs of the chromosomes. The hybridization sites coincided with the interstitial chromomycin A₃-bands or secondary constricted regions.

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Induction of endoreduplication in double minutes of the human neuroblastoma cells and the replication pattern

Susumu TAKAYAMA, Yukio HIRANO, Hisanao HIRAMATSU

1992 Volume 67 Issue 5 Pages 397-403
Published: 1992
Released on J-STAGE: October 19, 2005

DOIhttps://doi.org/10.1266/jjg.67.397

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Induction of endoreduplication (ERD) using Hoechst 33258 as well as colcemid was carried out in cultured neuroblastoma (NB) line cells. In these endoreduplicated cells, the majority of double minutes (DMs) appeared to take a diplochromosome like configuration to form a cluster consisting of four minute elements, assuming a complex DM. Sister chromatid differential staining (SCD) using 5-bromo-2'-deoxyuridine (BrdUrd) revealed the non-random distribution of the stained chromatids among four chromatids composing each diplochromosome, suggesting the occurrence of so-called "outside replication" of DNA strands during the process of ERD. The same pattern of differential staining was also found in the quadruple minutes of each endoreduplicated DM. Since DMs are acentric, the present results suggest that centromeres do not play any essential role in the formation of diplochromosomes observed in the conventional cytologic preparations and that centromeres are probably not responsible for the phenomenon of the "outside replication" of DNA strands.

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Chloroplast and mitochondrial DNAs of alloplasmic common wheat with cytoplasms of Agropyron glaucum, Ag. trichophorum and Haynaldia villosa

Tohru SUZUKI, Naoki MORI, Chiharu NAKAMURA, Ivan PANAYOTOV, Chukichi K ...

1992 Volume 67 Issue 5 Pages 405-414
Published: 1992
Released on J-STAGE: October 19, 2005

DOIhttps://doi.org/10.1266/jjg.67.405

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Cytoplasms of Agropyron glaucum, Ag. trichophorum and Haynaldia villosa are functionally different as revealed by several physiological characteristics of the alloplasmic lines having these cytoplasms and the same wheat nucleus. To find genetic differences among the cytoplasms of these species at molecular level, we studied chloroplast (ct) and mitochondrial (mt) DNAs using the alloplasmic lines. Cytoplasms of the two Agropyron species had closely related ctDNAs, whereas their mtDNAs differed greatly in their structure. As compared to the ct and mtDNAs of common wheat, those of the Agropyron species and Hy. villosa were found to have been equally diverged.

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Intersectional hybridization between Oryza australiensis Domin and O. ridleyi Hook

Taira KATAYAMA

1992 Volume 67 Issue 5 Pages 415-417
Published: 1992
Released on J-STAGE: October 19, 2005

DOIhttps://doi.org/10.1266/jjg.67.415

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One hybrid embryo of intersectional origin between Oryza australiensis Domin (W008, 2n=24) and O. ridleyi Hook. (W0001, 2n=48) was successfully obtained. The Fl hybrid had the expected chromosome number of 36 in the somatic cells. The average of meiotic chromosome pairing was 0.24II+34.27I. Meiotic irregularities, such as bridge, laggards and unequal separation of univalents were observed at almost all PMCs. This analysis leads to the conclusion that the two genomes of O. ridleyi differ from the EE genome of O. australiensis.

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