Sequential expression of myogenic regulatory factors in bovine skeletal muscle and the satellite cell culture

Myogenic regulatory factors (MRFs) are important in the control of skeletal muscle development. To understand myogenic regulation by MRFs in bovine adult muscle cells, their expressions, namely that of Myf5, MyoD, myogenin, and MRF4 in the biceps femoris muscle (BF) and in the satellite cell culture, were analyzed by RT-PCR. In the BF, all four MRFs were expressed and in particular, myogenin and MRF4 were strongly expressed, whereas Myf5 was faintly expressed. The satellite cells prepared from the BF expressed Myf5, but only a trace of MyoD, at day 9 of culture. During the growth of the cells to day 14, the MyoD and myogenin expressions gradually increased, and that of MyoD expression reached its maximum at the confluence of the culture. After induction of myogenic differentiation by a serum-free medium at day 14, Myf5 expression gradually decreased, and the up-regulated expression of MyoD was suppressed, whereas myogenin expression continued to increase sharply. Following the myogenin expression, MRF4 also drastically increased toward the myotube formation of the cells. When huge myotubes were formed at day 18, Myf5 was expressed at a low level, whereas the MyoD expression remained at a moderate level.     

First report of fig mosaic virus infecting common fig (Ficus carica) in Japan

For the first time, fig mosaic virus (FMV) was detected in common fig (Ficus carica) trees in Shimane, Japan. These trees exhibited mosaic, ringspots, or distortion, accompanied by chlorosis on leaves and yellow spots on fruits. Some of the symptomatic trees were infested with the eriophyid mite Aceria ficus. The virus was detected based on RT-PCR, followed by sequencing. The amplified 300 base-pair fragments shared 83.5–91.5% identity with the corresponding region of RNA-dependent RNA polymerase gene of FMV isolates previously reported in Turkey, Iran, and Italy.     

Powdery Mildew of Prairie Gentian: Characteristics,Molecular Phylogeny and Pathogenicity

In March 1999, we found prairie gentian (Eustoma grandiflorum) infected with powdery mildew in a greenhouse in Oita Prefecture, Japan. Morphological observation revealed that the causal fungus belongs to the mitosporic genus Oidium subgenus Pseudoidium [teleomorph: Erysiphe sensu Braun and Takamatsu (2000)]. Precise taxonomic position of the fungus, however, is uncertain due to lack of the perfect stage. We determined the nucleotide sequence of the rDNA ITS region of the fungus. Comparison of the sequence with those obtained from DNA databases of this fungal group revealed that the sequence is identical to those of powdery mildews from garden four-o'clock (Mirabilis jalapa) and broad bean (Vicia faba). Inoculation of an isolate from garden four-o'clock caused mildew on prairie gentian and broad bean, suggesting that the prairie gentian mildew originates from garden four-o'clock or broad bean. Molecular phylogenetic analysis indicated a close relationship of this fungus to Erysiphe baeumleri on Vicia spp. and E. trifolii on Trifolium pratense. From these results, we propose that prairie gentian mildew diverged from a Fabaceae-parasitic ancestor. Received 14 March 2002/ Accepted in revised form 28 May 2002     

Effects of topography and planted trees on the distribution of naturally regenerated broad-leaved trees in a 140-year-old <Emphasis Type="Italic">Cryptomeria japonica</Emphasis> plantation in northern Kyushu,Japan

We investigated factors affecting the distribution of naturally regenerated broad-leaved trees in a 140-year-old Cryptomeria japonica plantation. We used path analysis to examine the relationship among microtopography, the biomass of planted trees, and the biomasses of canopy and subcanopy trees of broad-leaved species. The study plot was divided into three topographic types (ridge, slope, and valley), and we discuss how the different topographic types are affected. For all topographic types, the biomass of canopy trees of broad-leaved species decreased with convexity. For slope and valley topographies, the biomass of subcanopy trees of broad-leaved species also decreased with convexity. For ridge topography, the biomass of subcanopy trees of broad-leaved species increased with the biomass of planted trees, and decreased with the biomass of canopy trees of broad-leaved species. These results suggest the effects of microtopography on the biomass of subcanopy trees were much larger than the effects of canopy trees for slope and valley topographies, while the effects of microtopography were smaller for ridge topography.     

Phytogeny and Cross-infectivity of Powdery Mildew Isolates (Podosphaera fuliginea s. lat.) on Cosmos and Cucumber

To clarify the relationship between the phylogeny and infectivity of isolates of Podosphaera fuliginea s. lat. (= Sphaerotheca fuliginea s. lat.) from cosmos and cucumber, more than 50 powdery mildew isolates from these two plants were subjected to nucleotide sequencing or PCR-RFLP analysis of the rDNA internal transcribed spacer (ITS) region and cross-inoculation tests. The isolates from both cosmos and cucumber are genetically monotypic, and there are six nucleotide substitutions in the rDNA ITS region between isolates from cosmos and cucumber. Cross-inoculation tests of these isolates revealed that isolates from cosmos are not pathogenic on cucumber. Although isolates from cucumber produced conidia on leaves of cosmos in the laboratory, the conidial density was much lower than that from isolates from cosmos. This result, as well as the fact that the cucumber strain was not isolated from cosmos in fields, suggests that isolates from cucumber do not infect cosmos in the field. Therefore, powdery mildews on cosmos and cucumber can be regarded to have become specialized for their hosts both genetically and pathogenically. The present study reconfirms the close relationship between phylogeny and infectivity of powdery mildew fungi. Host specialization may be a trigger that causes genetic divergence of powdery mildew fungi. Received 28 June 2000/ Accepted in revised form 4 September 2000     

Natural infection of Chrysanthemum stunt viroid in dahlia plants

For the first time, Chrysanthemum stunt viroid (CSVd) was detected in commercial dahlia bulbs in Japan. CSVd was found in 77.2% of the tested plants (Dahlia spp.). In nucleotide sequence analysis, a CSVd variant was detected consisting of 354 nucleotides, which differed slightly from previously reported CSVd variants. The nucleotide sequence data reported is available in the DDBJ/EMBL/GenBank databases under accession number AB255879.     

Morphological and molecular characterization of <Emphasis Type="Italic">Oidium</Emphasis> subgenus <Emphasis Type="Italic">Reticuloidium</Emphasis> (powdery mildew) newly occurred on cucumber in Japan

In 2002, a powdery mildew with catenate conidia lacking fibrosin bodies was found on cucumber in a greenhouse in Kanagawa Prefecture, Japan. Morphological observation revealed that the fungus belongs to Oidium subgenus Reticuloidium, anamorph of the genus Golovinomyces. Molecular phylogenetic analyses of the nucleotide sequences of the rDNA ITS regions and D1/D2 domains of the 28S rDNA indicated that the fungus belongs to the clade of G. orontii with other Golovinomyces fungi from a wide range of host plants, suggesting that the fungus was newly transported from abroad. Because there has been no prior report of cucumber powdery mildew caused by Reticuloidium, further research on the physiology, epidemiology, control and resistant cucumber varieties is required.     

Application of the first-order reaction (for) model to modulation by Bradyrhizobium japonicum in the modulation-dilution frequency method and estimation of time of initiation of nodulation

Abstract

Hattori (1985) proposed a model to simulate the relation between the number of bacterial colonies on agar plates and the incubation time, using the following equation:

where N(t) is the number of colonies observed at time t, and N_∞ λ, and t _r are parameters expressing the expected number of colonies observed at an infinite time, the rate of increase in the number of colonies, and the time of initiation of colony formation, respectively. This model is called the first-order reaction (FOR) model because the Eq. 1 is essentially the same as that of the first-order reaction.     

Development of late-bolting F<Subscript>1</Subscript> hybrids of Chinese cabbage (<Emphasis Type="Italic">Brassica rapa</Emphasis> L.) allowing early spring cultivation without heating

We developed new F₁ hybrids of Chinese cabbage (Brassica rapa L. ssp. pekinensis) that allow cultivation earlier in spring without heating by introducing extremely late-bolting alleles at two homologs of the flowering repressor Flowering Locus C (BrFLC2 and BrFLC3) from non-heading ‘Leafy Green Parental Line No. 2’. These new F₁ hybrids were produced by the following four steps. First, the extremely late bolting selected lines were developed. These selected lines headed in spring after overwintering cultivation, whereas the conventional F₁ cultivars flowered. Secondly, an investigation of the three plantings showed that our F₁ hybrids formed heads when seeds were sown from mid-February to early March, whereas the conventional F₁ cultivar did not form heads because of premature bolting. Thirdly, we identified some F₁ hybrids with extremely late bolting during early spring cultivation in an investigation of many F₁ hybrids. Finally, based on an investigation across four cold regions for 2 years, we compared the commercialization rate, defined as the proportion of plants greater than 2000 g in weight and with a flowering stalk less than 10 cm long. Then we identified a F₁ of MS02 × 12-04 which had a high commercialization rate on average (92%), whereas the rates of three conventional F₁ cultivars were only 0–2%. In the near future, these F₁ hybrids will be valuable late-bolting cultivars despite climate change, permitting stable cultivation and harvest over wide regions.