The speckled mutant of the Japanese morning glory blooms pale yellow flowers with fine and round colored spots, or speckles, distributed over the corolla. Since it also occasionally produces flowers with colored sectors apparently due to somatic mutations, the mutable speckled allele is thought to carry a transposable element. In this paper, we show that the appearance of the variegation phenotypes in the speckled mutant was controlled not only by the recessive speckled allele but also by a dominant genetic element, termed speckled-activator. Our results also indicated that the recessive c-1 mutation affecting pigmentation of flowers and mapped near the speckled locus causes a defect in a regulatory gene controlling the expression of structural genes for anthocyanin biosynthesis.

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The transformation technique in common wheat has already been established by using microprojectile bombardment and scutellar tissues of immature embryos. In this study, in vitro culture response of immature embryos and the production of transgenic wheat plants were examined in six common wheat cultivars, i.e., Chinese Spring, Akadaruma, Haruhikari, Shiroganekomugi, Norin 12, and Norin 61. In all genotypes, more than seven hundred immature embryos were bombarded with a plasmid containing a bialaphos-resistant gene under control of the rice actin 1 gene (Act1) promoter. Although the transient expression of the reporter gene encoding β-glucuronidase following the rice Act1 promoter was similar in five of the six cultivars tested, the frequency of stable transformation varied with the genotype. The frequency of transformation was the highest in Akadaruma and Norin 12 of the six wheat cultivars; independently transformed plants were produced from 1.4% and 1.7% of bombarded embryos, respectively. On the other hand, the immature embryos of Norin 61 and Shiroganekomugi showing low efficiency of in vitro culture generated no transgenic plants. This variation of the transformation frequency was generally caused by the difference in the in vitro culture response with the genotype, rather than the efficiency of the introduction of the transgene into wheat cells by particle bombardment.

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A nuclear genome of timopheevi wheat is compatible with the cytoplasm of Aegilops squarrosa, while that of durum wheat is incompatible, thus no euploid hybrids with this cytoplasm could be obtained. A euploid nucleus-cytoplasm (NC) hybrid of Triticum durum cv. Langdon was produced by introgressing a NC compatibility gene (Ncc-tmp) of T. timopheevi. Southern blot analysis, using one RAPD marker (S13₈₃₀) that is tightly linked to Ncc-tmp and DNAs from a series of D genome chromosome substitution lines of Langdon, demonstrated that Ncc-tmp locates on chromosome 1A. A similar function of Ncc-tmp and Ncc-sqr of Ae. squarrosa for its own cytoplasm suggested that they are homoeoallelic. Homologous sequences of two other linked RAPD markers (R03₈₂₀ and R19₆₀₀) were detected in all accessions of T. urartu but not in T. boeoticum. The result showed the conservation of sequences adjacent to Ncc-tmp in T. urartu, an A genome donor for emmer and timopheevi wheat. An analysis of γ-gliadin showed that the NC hybrid possesses one allele that might have been introgressed from chromosome 1G of T. timopheevi. Together with this result, 3:1 segregation of plump and shriveled seeds in BC₁ of the cross between (sqr)-T. timopheevi and T. turgidum suggested the presence of an additional and functional homoeoallelic Ncc-tmp in T. timopheevi.

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To elucidate mtDNA differentiation in the Japanese brown frog Rana japonica, and compare it with results from allozyme analysis and crossing experiments, RFLP analysis was conducted on 78 frogs from 16 populations in Honshu. Purified mtDNA was digested with eight six-base recognizing restriction enzymes and analyzed by 1% agarose-slab gel electrophoresis. Cleavage patterns of the mtDNA showed three distinct genome size classes: small (18.5 kb), middle (20.0 kb) and large (21.5 kb). Ten haplotypes (I~X) were observed among the 16 populations. The expected nucleotide divergences within populations ranged from 0 to 0.47% with a mean of 0.08%. The net nucleotide divergences among 16 populations ranged from 0 to 7.74% with a mean of 3.49%. The UPGMA dendrogram and NJ tree, which were constructed based on the net nucleotide divergences, showed that R. japonica diverged first into the eastern and western groups. The eastern group subsequently differentiated into a subgroup containing six populations and the Akita population, and the western group divided into several subgroups. These results, as well as the results of allozyme analysis and crossing experiments, suggest that the eastern and western groups have experienced secondary contact, and introgression has occurred in the Akita population.

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The products of the recG and ruvAB genes of Escherichia coli are both thought to promote branch migration of Holliday recombination intermediates by their junction specific helicase activities in homologous recombination and recombination repair. To investigate the in vivo role of the recG gene, we examined the effects of a recG null mutation on cell division and chromosome partition. After UV irradiation at a low dose (5J/m ²), ΔrecG mutant formed filamentous cells with unpartitioned chromosomes. A mutation in the sfiA gene, which encodes an SOS-inducible inhibitor of septum formation, partially suppressed filamentation of recG mutant cells, but did not prevent the formation of anucleate cells. The sensitivity to UV light and the cytological phenotypes after UV irradiation of a recA recG double mutant were similar to a recA single mutant, consistent with the role of recG, which is assigned to a later stage in recombination repair than recA. The recG ruvAB and recG ruvC double mutants were more sensitive to UV, almost as sensitive as the recA mutant and showed more extreme phenotypes concerning filamentation and chromosome nondisjunction, both after UV irradiation and without UV irradiation than either recG or ruv single mutants. The recG polA12 (Ts) mutant, which is temperature sensitive in growth, formed filamentous cells with centrally located chromosome aggregates when grown at nonpermissive temperature similar to the UV irradiated recG mutant. These results support the notion that RecG is involved in processing Holliday intermediates in recombination repair in vivo. We suggest that the defect in the processing in the recG mutant results in accumulation of nonpartitioned chromosomes, which are linked by Holliday junctions.

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Seven dominant marker genes controlling morphological characters of barley were introduced into a wheat genetic background through hybridization between a Japanese bread wheat cultivar, Shinchunaga, and barley marker stocks. F₁ hybrids and their derivatives were analyzed by C-banding to confirm the presence and dosage of particular barley chromosomes carrying the marker genes. The genes for black lemma (B, located on chromosome 1H), pubescent leaf blade (Pub, 3H), hairy leaf sheath (Hs, 4H) and hooded lemma (K, 4H) were expressed in the F₁ hybrids, but generally to a lesser extent than in the parental barley accessions. F ₁ hybrids having two copies of the B or Hs genes showed more pronounced pheno-types. In backcrossed progenies, each of which had a single copy of the barley marker gene in a hexaploid wheat background, the B and K phenotypes were less pronounced than in the F₁ hybrids, and the Pub phenotype was not observed. These four genes appear to be expressed in proportion to their dosage relative to the ploidy levels of the wheat background. The remaining three marker genes, brittle rachis (Bt-Bt2, 3H), blue aleurone (Bl, 4H) and short-upper-leaves (Sul) did not appear to express their characteristic phenotypes in any of the respective hybrids. Possible causes for reduced expression or complete suppression of the dominant barley genes in the wheat-barley hybrids are discussed. Dominant barley marker genes which are expressed in the hybrids would be useful for manipulating barley chromosomes in wheat backgrounds.

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Repetitive DNA sequences (Cal3nDr) in the genome of a triploid ginbuna (Carassius auratus langsdorfi) were isolated from the DraI digests of the genomic DNA. This AT-rich (61%) Cal3nDr monomer was 137 bp in length. The nucleotide similarity among the monomers from the same individual was considerably high (above 97%). Hybridization analyses revealed that the Cal3nDr sequences were organized into tandem arrays. These DNA sequences were present only in triploid and tetraploid ginbunas and were absent from diploid ginbuna, gengorobuna, goldfish, and other cyprinid fishes, and therefore appeared to be specific to polyploid ginbunas. In situ hybridization data showed their localization on one to four out of a total of 150 to 156 chromosomes, depending on the individuals or clonal lines, of the triploid ginbuna. The origin of the Cal3nDr sequences is also discussed on the basis of observation of the artificial triploid ginbuna produced by crossing a diploid female with a tetraploid male.

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A homologue of the rpoS gene of Escherichia coli was cloned from Vibrio cholerae N86 by complementation of the phenotypes of the E. coli rpoS mutant strain. We determined the DNA sequence of this gene. Sequence alignments have indicated that the rpoS gene of V. cholerae N86 encoding a 39-kDa protein is very similar to that of E. coli. In addition, the nlpD-like gene was found in the upstream region of the rpoS gene in the same order as in E. coli. These results suggest that the organization of these genes is highly conserved between E. coli and V. cholerae.

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