Effects of Host Cell Density on Cell Infection Level in Antheraea eucalypti (Lepidoptera: Saturniidae) Cell Cultures Persistently Infected with Nosema bombycis (Microsporida: Nosematidae)

ABSTRACT. Spores of Nosema bombycis Y9101, isolated from the beet armyworm, Spodoptera exigua , were primed with an alkaline solution and inoculated into Antheraea eucalypti cell cultures. Infected cells were subcultured every five days at three cell densities (2.5 × 10³, 5.0 × 10³, and 1.0 × 10⁴ cells/cm²). A difference was observed in the spread of N. bombycis Y9101 infection between low-density and higher-density cultures of host cells. The host cell density did not affect the productivity of secondary infective forms of the parasite. The principal factor determining the rate of microsporidian infection in vitro was the number of host cells existing within the reach of extruded short-coiled polar tubes from spores germinated intracellularly.     

Inhibitory Action of Blue and Far-Red Light in the Flowering of Lemna paucicostata

In a new strain of short-day duckweed (Lemna paucicostata T-101), blue and far-red light-induced inhibition of flowering was investigated. Flowering of this strain failed to be induced under a short-day photoperiod of blue and far-red light, although it responded as a typical short-day plant in red and white light. When the short-day photoperiod of blue or far-red light was terminated by a 15 min red light pulse, flowering recovered completely. This inducing effect of red light was reversed by subsequent exposure to far-red light. Furthermore, it could be demonstrated that 30 min of blue light completely reversed the flowering inductive effect of 5 min red light and vice versa. Evidence is presented suggesting that the inhibitory action of blue and far red light may be due to the lowering of phytochrome P_fr levels below those required to start the dark reactions which lead to flowering. These results are discussed in relation to the time measurement system of photoperiodism.     

Cytokinin Activity of Benzoylaminodeazapurines, Pentanoylaminodeazapurines and their Corresponding Purine Analogs in Five Bioassays

Cytokinin activities of 6-benzoylamino-1, 6-benzoylamino-3-, 6-pentanoylamino-1- and 6-pentanoylamino-3-deazapurines and their corresponding purine analogs, 6-benzoylaminopurine and 6-pentanoylaminopurine, were examined using five bioassay systems, tobacco callus growth, bud formation on tobacco callus, lettuce seed germination, fresh weight increase of radish cotyledons and retardation of chlorophyll degradation in radish cotyledons. 6-Benzoylamino- and 6-pentanoylamino-1-deazapurines showed stronger cytokinin activity than their corresponding purine analogs in all bioassays used. In tobacco callus growth, 6-benzoylamino-1-deazapurine was nearly as active as zeatin, one of the most active adenylate cytokinins. On the other hand, 6-benzoylamino- and 6-pentanoylamino-3-deazapurines were as active as or less active than corresponding purine analogs.     

Studies on the metabolism of a sulfur-oxidizing bacterium IV.1 Growth and oxidation of sulfur compounds in Thiobacillus thiooxidans

By immersing a few small cellophane bags containing BaCO³ powderin STARKEY's medium, the duration of lag phase in the growthof Thiobacillus thiooxidans is minimized and the yield of cellsis increased ten times that of the previous method. The activitiesof oxidation for sulfur and sulfite change with growth. Sulfiteis oxidized at a comparable rate to that of sulfur oxidationat pH values between 6.0 and 6.5. In the presence of cysteineor glutathione, thiosulfate can be oxidized at a pH above 5.0.At pH values below 4.5, apparent oxidation of thiosulfate andtetrathionate to sulfate is observed. This result is accountedfor by the facts that thiosulfate is decomposed to sulfur andsulfite under the acidic condition at pH values below 4.5, andthat tetrathionate is reduced to thiosulfate enzymatically.In the oxidation of tetrathionate, oxygen uptake begins aftera lag phase, the duration of which depends on the concentrationsof cells and of tetrathionate. Cysteine is oxidized to cystine.The oxidation is strongly inhibited by metal-chelating agents.The cysteine oxidizing activity is, however, quite stable andis not lost by treating cells with organic solvents, sonic oscillation,by heating or lyophilization. ¹III=References (11). ²Partly supported by a grant from the Ministry of Education.     

Fourteen polymorphic microsatellite loci in the field gudgeon,Gnathopogon elongatus elongatus

We isolated and characterized 14 polymorphic microsatellite loci for the field gudgeon, Gnathopogon elongatus elongatus, a popular freshwater species in streams including agricultural canals in Japan. The number of observed alleles for each locus ranged from 9 to 24, and the values of observed and expected heterozygosities ranged from 0.750 to 1.000 and from 0.832 to 0.953, respectively. These microsatellite markers will be useful for studies of population genetic structure and genetic variability of the field gudgeon.     

Heritability and genetic correlation of abdominal versus caudal vertebral number in the medaka (Actinopterygii: Adrianichthyidae): genetic constraints on evolution of axial patterning?

Variation in the number of abdominal vs. caudal vertebrae is an important source of morphological diversification of fish. It is not clear, however, whether abdominal and caudal regions evolve independently. Regressions of offspring on parents demonstrated substantial additive genetic variation within populations, i.e. heritability, in both abdominal and caudal vertebral numbers of the medaka ( Oryzias latipes ). However, the heritability of caudal vertebrae tended to be smaller than that of abdominal vertebrae in some estimations, suggesting that abdominal and caudal regions are controlled by separate developmental modules. Furthermore, genetic correlation between abdominal and caudal vertebral numbers, estimated using full-sib family means, was negative but weak, supporting independent evolution. In addition, substantial genetic differentiation among populations was demonstrated in abdominal vertebral numbers, but not in caudal numbers. These results support our view that Jordan's rule, a geographical tendency for fish from higher latitudes to have more vertebrae, in this fish reflects local adaptations of abdominal vertebral numbers. In contrast, the low heritability of caudal vertebrae may reflect the intrinsic invariability of genes associated with a change in caudal vertebral numbers. This genetic constraint may have restricted morphological diversification of not only the medaka, but also the Order Beloniformes as a whole.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 96 , 867–874.     

Morphological adaptations of emergent plants to water flow: a case study with Typha angustifolia, Zizania latifolia and Phragmites australis

1. Water velocity plays an important role in shaping plant community structure in flowing waters although few authors have yet attempted to explain the adaptation of plants to flow. 2. We aimed to test two hypotheses, that: (i) some emergent macrophytes reconfigure their shoot distribution in fast currents and form clumps, and (ii) the shape and morphology of such clumps minimises drag caused by the current. The study focuses on three emergent macrophytes that co‐occur along a gradient of water velocity. 3. The species showed a clear zonation in response to water depth and current velocity. Phragmites australis occupied shallower and more slowly flowing water than Typha angustifolia and Zizania latifolia, which had similar preferences. 4. Both T. angustifolia and Z. latifolia shoots were more clumped at high velocity, whereas they were more randomly distributed at low flow or in stagnant water. Because of the low shoot density, water flowed more easily through T. angustifolia clumps, whereas Z. latifolia clumps had a high shoot density and large amounts of trapped litter, causing stagnant water in the centre of the clump. The clumps of Z. latifolia with a high density of shoots were longer and narrower than T. angustifolia clumps. Phragmites australis was less tolerant of flow than the other two species and large amounts of litter trapped in the clumps impaired flow. 5. The shoot distribution of both T. angustifolia and Z. latifolia is reconfigured at high flow and this minimises drag on the clumps.     

Change in CO2 balance under a series of forestry activities in a cool-temperate mixed forest with dense undergrowth

To evaluate the effects on CO₂ exchange of clearcutting a mixed forest and replacing it with a plantation, 4.5 years of continuous eddy covariance measurements of CO₂ fluxes and soil respiration measurements were conducted in a conifer-broadleaf mixed forest in Hokkaido, Japan. The mixed forest was a weak carbon sink (net ecosystem exchange, −44 g C m⁻² yr⁻¹), and it became a large carbon source (569 g C m⁻² yr⁻¹) after clearcutting. However, the large emission in the harvest year rapidly decreased in the following 2 years (495 and 153 g C m⁻² yr⁻¹, respectively) as the gross primary production (GPP) increased, while the total ecosystem respiration (RE) remained relatively stable. The rapid increase in GPP was attributed to an increase in biomass and photosynthetic activity of Sasa dwarf bamboo, an understory species. Soil respiration increased in the 3 years following clearcutting, in the first year mainly owing to the change in the gap ratio of the forest, and in the following years because of increased root respiration by the bamboo. The ratio of soil respiration to RE increased from 44% in the forest to nearly 100% after clearcutting, and aboveground parts of the vegetation contributed little to the RE although the respiration chamber measurements showed heterogeneous soil condition after clearcutting.