Offshore currents explain the discontinuity of a fish community in the seagrass bed along the Japanese archipelago

Oceanographic conditions can affect spatial variability in fish community structures by influencing the temperature‐dependent latitudinal distribution of adult fishes and transport during their young stages. In order to examine latitudinal variability in the fish community structure within a single coastal ecosystem, quantitative sampling was conducted in the sub‐tidal zone of seagrass Zostera marina beds over a broad latitudinal scale (31.31–43.0°N: from subtropical to sub‐boreal zones, covering 80% of the latitudinal range of seagrass distribution in Japan) in the western North Pacific based on a uniform methodology. Cluster analysis with the similarity of fish communities showed that 13 sampling sites were divided into two clusters. The border between the two clusters corresponded with the area of mixing of two dominant currents, Oyashio and Kuroshio, which form a border between the warm temperate zone and the cool temperate zone off the Pacific coast of Japan. Oceanographic properties, such as major currents off the coast, are suggested to affect the latitudinal variability in the fish communities in the coastal ecosystem in the western North Pacific.     

Proportion and cluster analyses of the skull in various species of the tree shrews

The skull adaptation was functional-morphologically examined in 14 species of the tree shrews. From the data of the proportion indices, the similarities were confirmed between T. minor and T. gracilis, T. tana and T. dorsalis, and T. longipes and T. glis. We demonstrated that the splanchnocranium was elongated in terrestrial T. tana and T. dorsalis and shortened in arboreal T. minor and T. gracilis from the proportion data. In both dendrogram from the matrix of the Q-mode correlation coefficients and scattergram from the canonical discriminant analysis, the morphological similarities in the skull shape suggested the terrestrial-insectivorous adaptation of T. tana and T. dorsalis, and the arboreal adaptation of T. minor and T. gracilis. Since the osteometrical skull similarities were indicated among the three species of Tupaia by cluster and canonical discriminant analyses, the arbo-terrestrial behavior and its functional-morphological adaptation may be commonly established in T. montana, T. longipes and T. glis.     

Decreasing traits of fecal immunoglobulin A in neonatal and weaning piglets

The concentration of fecal secretory immunoglobulin A (sIgA) in neonate and weaning piglets was measured daily from 1 day after birth to 50 days of age. The concentration of fecal sIgA started from the level of 10(4) microg/g wet feces 1 day after birth and then increased to a maximal value of up to 10(5) microg/g within a few days of birth. The values constantly declined to between 10(1) and 10(2) microg/g for the next 10 days and were relatively constant until weaning. The level of sIgA in the feces remained very low until at least 50 days of age. The vulnerability of pre- or post-weaning piglets can be explained, at least in part, by this low level of sIgA in the intestine.     

Chromosomal location of Hwc2, one of the complementary hybrid weakness genes, in rice

A hybrid weakness phenomenon is controlled by a set of complementary genes, Hwc1 (hybrid weakness c) and Hwc2, in rice. The Hwc2 gene is prevalent among temperate Japonica but not among tropical Japonica or Indica. In this study, the chromosomal location of the Hwc2 locus was determined from the segregation in the F₁ hybrids made between 127 recombinant inbred lines and the cultivar ‘Jamaica’. Hwc2 was located between the two restriction fragment length polymorphism loci, XNpb264 and XNpb197 on chromosome 4. Further analysis indicated that Hwc2 was closely linked to Ph (phenol staining). The genetic and phylogenetic significance of the Hwc2 locus and the surrounding chromosomal region is discussed.     

Mapping of quantitative trait loci controlling seed longevity of rice (Oryza sativa L.) after various periods of seed storage

Seed longevity varies considerably in cultivated rice (Oryza sativa L.), but the underlying genetic mechanism of longevity has not been well elucidated. Quantitative trait loci (QTL) that control seed longevity after various periods of seed storage were sought using recombinant inbred lines derived from a combination involving ‘Milyang23’(Indica‐type) and ‘Akihikari’ (Japonica‐type). In all, 12 QTLs for germination and normal seedling growth were detected as indices of seed longevity on chromosome 7 (one region) and chromosome 9 (two regions) in treated seeds that had been stored under laboratory conditions for 1, 2 or 3 years.‘Milyang23’ alleles of all QTLs promoted germination and normal seedling growth after all durations of storage. These QTL regions were detected repeatedly in more than one seed condition. Therefore, we infer that these regions control seed longevity.     

Carotenoid accumulations and carotenogenic gene expressions in the petals of Eustoma grandiflorum

Eustoma grandiflorum is one of the leading cut‐flowers in Japan. There are market demands for cultivars with deep‐yellow flowers, but they have never been bred successfully. By investigating the carotenoid accumulation and carotenogenic gene expressions, this study attempted to explore the reasons that block the formation of deep‐yellow colour in Eustoma. High performance liquid chromatography analysis showed that the carotenoid compositions in petals were similar to those in leaves, accumulating mainly lutein, violaxanthin and β‐carotene. The total carotenoid contents decreased as the petals matured in all the cultivars tested. Quantitative real‐time PCR analysis showed that the expression levels of PSY, LCYB, ZDS and LCYE showed significant differences between white and pale‐yellow petals or between petals and leaves, indicating that these enzymes may play a key role in the carotenoid biosynthesis in E. grandiflorum. The expression levels of CCD4 were high in both pale‐yellow and white petals during development, suggesting that carotenoid degradation activity is high in the petals. We then conclude that the total carotenoid accumulation level could be determined by the balance between carotenoid biosynthesis and degradation activities.     

Genetic variation in resistance to blast disease (Pyricularia oryzae Cavara) in Japanese rice (Oryza sativa L.), as determined using a differential system

A total of 324 Japanese rice accessions, including landrace, improved, and weedy types were used to 1) investigate genetic variations in blast resistance to standard differential isolates, and 2) across the genome using polymorphism data on 64 SSR markers. From the polymorphism data, the accessions were classified into two clusters. Accessions from irrigated lowland areas were included mainly in cluster I, and upland and Indica types were mainly in cluster II. The accessions were classified into three resistance subgroups, A2, B1 and B2, based on the reaction patterns to blast isolates. The accessions in A2 were postulated to have at least two resistance genes Pish and Pik-s, whereas those in B1 had various combinations of the resistance genes Pish, Pia, Pii, Pi3, Pi5(t), and Pik alleles. The B2 accessions were resistant to almost all isolates, and many accessions of cluster II were included, and had Pish, Pia, Pii, Pi3, Pi5(t), certain Pik, Piz and Pita alleles, and unknown genes. The frequencies of accessions of B1 originating in Hokkaido, and those of B2 originating in the Kanto and Tohoku regions were remarkably higher than in the other regions.