To determine the phylogenetic relationship of six species (Dioscorea gracillima, D. nipponica, D. quinqueloba, D. septemloba, D. tenuipes, and D. tokoro) in the section of Stenophora in the genus of Dioscorea, nucleotide sequence variation in 1073 bp of coding region of the phosphoglucose isomerase (Pgi) locus was analyzed. Estimates of nucleotide diversity (π) for D. gracillima, D. quinqueloba, D. tenuipes, and D. tokoro were 0.0020, 0.0005, 0.0025, and 0.0013, respectively. Deviation from neutrality in the pattern of polymorphism in these four species was not detected by the Tajima's test. The difference in the pattern of amino acid substitutions between divergence and polymorphism was not observed by McDonald and Kreitman test. The obtained phylogenetic trees indicated that D. tokoro and D. tenuipes belonged to a monophyletic clade, while the other four species formed a separate monophyletic group. The branch lengths of phylogenetic tree varied among species. D. nipponica had a significantly faster substitution rate compared to D. gracillima, D. quinqueloba, and D. septemloba.

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In the medaka, Oryzias latipes, which does not have cytologically recognizable sex chromosomes, the mechanism of sex determination (XX/XY) can be revealed by genetic crosses using a particular pigment gene. Since the only known sex-linked marker is this pigment gene, little information is available on the genetic maps of the medaka's sex chromosomes. High resolution genetic maps of its sex chromosomes are necessary to hunt for the sex-determining factor by the positional cloning method. In the present study, we isolated a sex-linked marker using the genomic differences between inbred strains of medaka. We established a congenic strain whose sex-determining region is derived from the HNI strain and whose genetic background is derived from the Hd-rR strain. Using differences between the genomes of the congenic and Hd-rR strains, we isolated a sex-linked clone (pHO5.5) from a random genomic library constructed from the HO5 strain of medaka. The pHO5.5-related sequences were conserved among Oryzias species. A linkage analysis using backcross progeny from the Hd-rR and HNI strains demonstrated perfect linkage between the pHO5.5-related sequence and the sex. We, hence, designated the locus of the pHO5.5-related sequence on sex chromosomes of medaka as Sex-Linked 1 (SL1). Using this sequence, we could identify the sex of inbred strains of medaka by PCR or Southern blotting. This sequence may be useful for genetic mapping on the sex chromosomes. We also discuss the availability of the congenic strain established in this study for isolating other sex-linked clones.

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Seven species of the Drosophila melanogaster species subgroup were compared for mating success under different light conditions (light or dark). All species except D. melanogaster showed a significantly lower frequency of mating success in the dark than in light in a one-hour mating experiment. Among the six light-dependent species, D. sechellia showed the lowest frequency in the dark and D. simulans showed the highest in the dark. They were chosen for further intraspecific comparisons using four strains respectively. A substantial difference in the mating frequency in the dark was again found among the four strains in both D. sechellia and D. simulans, respectively. In these two species reciprocal mating experiments were then performed between the two strains showing the highest and the lowest frequency in the dark. In both species males from the strains with a low mating frequency also showed low scores with the females from the strain that showed a high score. It is therefore shown that males predominantly contribute to the low frequency of mating success in the dark while females appear to make a negligible contribution to the light dependency of mating. The male flies in both D. sechellia and D. simulans showing high mating frequency did not always show a high locomotor level under light or in the dark. We conclude that the decrease of the mating frequency in the dark is caused by the light-dependent mechanism of male-specific sexual behavior rather than by a mechanism associated with general activity.

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Because the males of the Drosophila melanogaster species subgroup contributed to the light dependency of mating success and this was not due to the light-dependent nature of general activity, we have suggested that the light dependency of mating is caused by the light-dependent mechanism of male-specific sexual behavior. Courtship behavior of the wild type males of D. melanogaster was investigated in light and dark with a female partner with a severe norpA mutation. Total duration, frequency and bout length of all courtship elements, except for bout length of orientation and attempted copulation, were significantly lower in the dark than in light. Particularly, male following behavior was strongly affected by light. The sequence analysis of courtship behavior revealed that the courtship transition from orientation to following was severely disturbed in the dark. An unique transition from orientation to wing vibration, skipping the following phase was frequently observed in the dark. Under dim red light, single males showed a similar high locomotor activity in the dark as in light during the period over which male courtship behavior was investigated and analysed. It was suggested that the male following behavior requires visual cues and that the following is the major behavioral element involved in the light dependency of mating in Drosophila.

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Genetic fixation in finite populations under different degrees of restriction of pollen flow in an animal-pollinated allogamous plant species was investigated through computer simulation. A single locus with two alleles in a population of self-incompatible, diploid plants was considered. A gene-pool model, a random pollen flow model and a neighborhood model were also included for comparison. Under restricted pollen flow models, the fixation probability was depressed considerably in comparison with the gene-pool model. To distinguish the effect of patch formation, plants were relocated randomly just after mating at each generation. The extent of probability of an increase in fixation was manifested for restricted pollen flow models and a random pollen flow model. The random pollen flow model with relocation exhibited an even lower fixation probability than the gene-pool model. This departure can be ascribed to zygote formation, which is not accounted for in the gene-pool model. In conclusion, the depression of fixation observed for restricted pollen flow models is due not only to patch formation caused by pollen flow restriction, but also to zygote formation. Any theoretical model based on the gene-pool model is misleading when attempting to understand the genetic properties of a natural plant population, since neither of these two factors is taken into account.

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The general method of segregation analysis of pedigree data has been developed and widely used in human genetics. We modified this method to examine pedigree data coming from inter-population crosses. These kinds of pedigrees are common in laboratory and farm animal breeding. This paper describes a rationale for the method and illustrates its application to the study of inheritance of litter size and of male sterility in hybrid stock of the house musk shrew (Suncus murinus) derived from crosses of two geographically isolated populations.

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Hybrids not carrying Drosophila simulans X chromosome derived from the cross between D. melanogaster females and D. simulans males are lethal at the late third instar larval period or early pupal stage. This lethality can be rescued by the mutation Lethal hybrid rescue (Lhr) of D. simulans. The Lhr gene is considered to play an important role in reproductive isolation, but the genetic analyses have not been carried out extensively because of the lack of visible mutations and chromosome rearrangements in D. simulans. Using a cuticle mutation, jabara, of which locus is close to Lhr, and D. melanogaster deficiencies, we performed cytological mapping in hybrids and estimated the Lhr locus to 54E-F.

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The Afa-family repetitive sequences were isolated from barley (Hordeum vulgare, 2n = 14) and cloned as pHvA14. This sequence distinguished each barley chromosome by in situ hybridization. Double color fluorescence in situ hybridization using pHvA14 and 5S rDNA or HvRT-family sequence (subtelomeric sequence of barley) allocated individual barley chromosomes showing a specific pattern of pHvA14 to chromosome 1H to 7H. As the case of the D genome chromosomes of Aegilops squarrosa and common wheat (Triticum aestivum) hybridized by its Afa-family sequences, the signals of pHvA14 in barley chromosomes tended to appear in the distal regions that do not carry many chromosome band markers. In the telomeric regions these signals always placed in more proximal portions than those of HvRT-family. Based on the distribution patterns of Afa-family sequences in the chromosomes of barley and D genome chromosomes of wheat, we discuss a possible mechanism of amplification of the repetitive sequences during the evolution of Triticeae. In addition, we show here that HvRT-family also could be used to distinguish individual barley chromosomes from the patterns of in situ hybridization.

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An Arabidopsis cDNA encoding putative phospholipid hydroperoxide glutathione peroxidase (PHGPX) was cloned and sequenced. The cDNA comprised 803 bp and included an open reading frame which encodes a polypeptide of 169 amino acid residues. The deduced amino acid sequence showed about 80 and 50% homology with plant putative PHGPXs and mammalian PHGPXs, respectively. Southern blot analysis suggested that the putative PHGPX gene was a single-copy gene. The expression profile of the putative PHGPX in Arabidopsis under NaCl and Al/Fe treatments, which generate oxidative stress, was analyzed. Northern blot analysis revealed that the Arabidopsis putative PHGPX mRNA levels were increased about 3 and 4.5 times after exposure to NaCl and Al/Fe, respectively. These results suggest that the putative PHGPX gene is induced by oxidative stress in Arabidopsis.

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Polymerase chain reaction (PCR) with degenerate primers was utilized for partial cloning of the MADS box gene family from wheat (Triticum aestivum L.). PCR products corresponding to a part of the MADS box region were cloned and sequenced. Eleven individual clones sequenced were classified into seven types on the basis of the nucleotide sequence and five types on the deduced amino acid sequence, which included two wheat-specific MADS box protein sequences. RT-PCR analysis with degenerate primers revealed preferential expression of the MADS box genes in young spikes. Furthermore, genomic Southern blot analysis with degenerate PCR products as probes indicated that wheat MADS box genes constitute a multigene family and are dispersed throughout the genome.

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