Genes & Genetic Systems
Online ISSN : 1880-5779
Print ISSN : 1341-7568
ISSN-L : 1341-7568
77 巻, 1 号
選択された号の論文の8件中1~8を表示しています
Full Papers
  • Misugi Uraji, Katsunori Suzuki, Kazuo Yoshida
    原稿種別: Full papers
    2002 年 77 巻 1 号 p. 1-9
    発行日: 2002年
    公開日: 2002/04/16
    ジャーナル フリー
    Ti (Tumor inducing) plasmids in Agrobacterium tumefaciens can transfer their T-DNA region into dicotyledonous plants, in which the expression of T-DNA genes causes plant tumors and the production of bacterial nutrients, e.g., opines such as nopaline. Naturally occurring Ti plasmids (pTi) are difficult to cure by conventional curing methods because of their high stability. Here, we developed a novel curing method based on plasmid incompatibility. For this, a curing plasmid, pMGTrep1, was newly constructed and subsequently introduced into A. tumefaciens strains harboring pTi by conjugation with Escherichia coli harboring pMGTrep1. The conjugation yielded 32-99% nopaline non-utilizing agrobacterial transconjugants in which pMGTrep1 replaced pTi due to incompatibility. Then, pMGT rep1-less derivatives of the transconjugants are easily selected in the presence of sucrose because pMGTrep1 contains a sucrose-sensitive sacB gene. This efficient method is directly applicable for curing plasmids with the same incompatibility group and shoud also applicable to other types of plasmids in Agrobacterium groups, including A. rhizogenes, by replacing the rep gene region of the curing plasmid with that of the corresponding incompatibility.
  • Ryoko Onodera, Masayuki Seki, Ayako Ui, Yurie Satoh, Atsuko Miyajima, ...
    原稿種別: Full papers
    2002 年 77 巻 1 号 p. 11-21
    発行日: 2002年
    公開日: 2002/04/16
    ジャーナル フリー
    A mutant allele of SGS1 of Saccharomyces cerevisiae was identified as a suppressor of the slow-growth phenotype of top3 mutants. We previously reported the involvement of Top3 via the interaction with the N-terminal region of Sgs1 in the complementation of methylmethanesulfonate (MMS) sensitivity and the suppression of hyper recombination of a sgs1 mutant. In this study, we found that several amino acids residues in the N-terminal region of Sgs1 between residues 4 and 33 were responsible for binding to Top3 and essential for complementing the sensitivity to MMS of sgs1 cells. Two-hybrid assays suggested that the region of Top3 responsible for the binding to Sgs1 was bipartite, with portion in the N- and C-terminal domains. Although disruption of the SGS1 gene suppressed the semi-lethality of the top3 mutant of strain MR, the sgs1-top3 double mutant grew more slowly and was more sensitive to MMS than the sgs1 single mutant, indicating that Top3 plays some role independently of Sgs1. The DNA topoisomerase activity of Top3 was required for the Top3 function to repair DNA damages induced by MMS, as shown by the fact that the TOP3 gene carrying a mutation (Phe for Tyr) at the amino acid residue essential for its activity (residue 356) failed to restore the MMS sensitivity of sgs1-top3 to the level of that of the sgs1 single mutant. Epistatic analysis using the sgs1-top3 double mutant, rad52 mutant and sgs1-top3-rad52 triple mutant indicated that TOP3 belongs to the RAD52 recombinational repair pathway.
  • Zhi-Jun Cheng, Minoru Murata
    原稿種別: Full papers
    2002 年 77 巻 1 号 p. 23-29
    発行日: 2002年
    公開日: 2002/04/16
    ジャーナル フリー
    The advanced lines of octoploid triticale which have been bred for nearly a half century in China show significant improvements in agronomic traits such as plant height, fertility, threshability, maturity and seed plumpness, although no intentional cytological selection had been performed. In this study, eight primary and six advanced lines were analyzed by fluorescence and genomic in situ hybridization to elucidate their chromosome constitutions. In the advanced lines, about 70% of the plants examined had 2n = 56 chromosomes (range: 50 to 58). Almost all advanced lines, however, had lost rye chromosome 2R and the short arm of 5R (5RS). The exceptions were lines Y1005 and Y4683: The former had lost only the 2R chromosome and the latter only 5RS. The reduction of rye chromosomes was compensated by an extra pair of 2D or A-genome (possibly 2A) chromosomes in plants with 2n = 56. This suggests that the loss of 2R and 5RS chromosomes contributes to the improvement of octoploid triticale. Since the plants with chromosome 2R are non-free threshing and chromosome 2D of synthetic wheat is known to carry the Tg (tenacious glumes) gene, it is possible that chromosome 2R carries a gene affecting the threshability, and we carried out selection to remove it. We also discuss the possible relationship between 5RS and the genetic stability of octoploid triticale.
  • Hiroaki Saika, Kazuhiro Ohtsu, Sawako Hamanaka, Mikio Nakazono, Nobuhi ...
    原稿種別: Full papers
    2002 年 77 巻 1 号 p. 31-38
    発行日: 2002年
    公開日: 2002/04/16
    ジャーナル フリー
    A novel gene for alternative oxidase (AOX) was isolated from rice (Oryza sativa L.) and characterized. The deduced amino acid sequence of the novel AOX gene contains features that are conserved among other AOXs. This AOX gene was designated AOX1c based on a phylogenetic analysis of the AOX genes. Northern hybridization analyses revealed that AOX1c and AOX1a/AOX1b transcripts accumulated differently in various rice organs and rice seedlings under low temperature conditions. AOX1c mRNA was mainly present in young leaves under constant light, mature leaves and panicles after heading, but it was not detected in young etiolated leaves and young roots of seedlings or young panicles. On the other hand, the mRNAs of the rice AOX1a and AOX1b genes were mainly present in young roots and mature leaves. Under low temperature conditions, the steady-state mRNA levels of the rice AOX1a and AOX1b genes clearly increased with time but the rice AOX1c gene was apparently not responsive to low temperature. The rice AOX gene family and differences in their regulation are discussed.
  • Junko Noguchi
    原稿種別: Full papers
    2002 年 77 巻 1 号 p. 39-50
    発行日: 2002年
    公開日: 2002/04/16
    ジャーナル フリー
    Chromosome configurations and structures during meiotic prophase were investigated by staining large repeated DNA sequences localized in the subtelomeric regions of all the chromosomes in rye, Secale cereale, in order to clarify when and how homolog pairing and bouquet formation occur. The changes of the spatial locations of chromosomes in the nucleus were investigated by the use of laser confocal microscopy, together with the surface-spreading method of silver nitrate staining to detect the formation of the synaptonemal complex. Homolog pairing in which homologs of four chromatids of a pair of homologs were coaligned in parallel but remained distinctly separate was microscopically detected for the first time in the present study. Homolog pairing showed the following characteristics: (1) it occurred at the leptotene-zygotene transition stage, prior to the formation of nodules and the synaptonemal complex; (2) the chromatin structure of chromosomes was in a state of decondensation; (3) it required no telomere clustering. These data suggest that homolog pairing represents a structure that indicates incipient recombination. After the homolog pairing stage, two kinds of bouquet configuration were found in zygotene. The commonly observed type was a loose bouquet, in which the subtelomeric regions were loosely aggregated. The other type was a definite bouquet, in which almost all the subtelomeric regions were conjugated, but this type was observed only in a limited number of the meiotic prophase cells of some individuals. It was concluded that the former represents the configuration of homologous recombination and the latter that of ectopic recombination.
  • Juan Carlos Parejo, José Angel Padilla, Araceli Rabasco, M Esth ...
    原稿種別: Full papers
    2002 年 77 巻 1 号 p. 51-58
    発行日: 2002年
    公開日: 2002/04/16
    ジャーナル フリー
    RAPD analyses have been used to determine the genetic diversity and the population structure of the endangered Blanca Cacereña bovine breed. Genetic variability was evaluated on the basis of 1048 loci produced by 71 primers. RAPD produced a number of polymorphic loci (30.44%), and it has been proved to be a useful method for evaluating polymorphisms in this breed. The dendrograms based on simililarity indexes and on Nei's genetic distances between 60 animals and the value of genetic differentiation among subpopulations (FST) showed a clear population substructure defined by herds and a scarce genetic flow among herds. Analysis of molecular variance (AMOVA) showed that 32.4% of the total variance was due to differences among herds and confirmed the clustering found. The results of the present study allow us to plan more adequate mating in order to maintain the genetic diversity and to improve the efficiency of conservation for the Blanca Cacereña bovine breed.
  • Yoshinobu Sugino, Aiko Umemoto, Satoshi Mizutani
    原稿種別: Full papers
    2002 年 77 巻 1 号 p. 59-62
    発行日: 2002年
    公開日: 2002/04/16
    ジャーナル フリー
    Sensitivity to the bitter taste of chloramphenicol was studied in 860 students, 620 males and 240 females. About 8.6% of them were insensitive to this bitter taste. Familial lineage studies were carried out on a subset of these students, and the results suggested that the sensitivity or insensitivity was controlled by a pair of autosomal Mendelian genes, with the sensitive gene being dominant over the insensitive.
Short Communications
  • Wakana Uchida, Sachihiro Matsunaga, Ryuji Sugiyama, Shigeyuki Kawano
    原稿種別: Short Communications
    2002 年 77 巻 1 号 p. 63-67
    発行日: 2002年
    公開日: 2002/04/16
    ジャーナル フリー
    Eukaryotic chromosomal ends are protected by telomeres, which are thought to play an important role in ensuring the complete replication of chromosomes. On the other hand, non-functional telomere-like repeats in the interchromosomal regions (interstitial telomeric repeats; ITRs) have been reported in several eukaryotes. In this study, we identified eight ITRs in the Arabidopsis thaliana genome, each consisting of complete and degenerate 300- to 1200-bp sequences. The ITRs were grouped into three classes (class IA-B, class II, and class IIIA-E) based on the degeneracy of the telomeric repeats in ITRs. The telomeric repeats of the two ITRs in class I were conserved for the most part, whereas the single ITR in class II, and the five ITRs in class III were relatively degenerated. In addition, degenerate ITRs were surrounded by common sequences that shared 70-100% homology to each other; these are named ITR-adjacent sequences (IAS). Although the genomic regions around ITRs in class I lacked IAS, those around ITRs in class II contained IAS (IASa), and those around five ITRs in class III had nine types of IAS (IASb, c, d, e, f, g, h, i, and j). Ten IAS types in classes II and III showed no significant homology to each other. The chromosomal locations of ITRs and IAS were not category-related, but most of them were adjacent to, or part of, a centromere. These results show that the A. thaliana genome has undergone chromosomal rearrangements, such as end-fusions and segmental duplications.
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