Lymphocystis disease virus persists in the epidermal tissues of olive flounder, Paralichthys olivaceus (Temminch & Schlegel), at low temperatures

Olive flounder artificially infected with lymphocystis disease virus (LCDV) were reared at 10, 20 and 30 °C for 60 days, to compare LCD-incidence. In the fish reared at 20 °C, lymphocystis cells appeared on the skin and fins at 35 days post-challenge, and the cumulative LCD-incidence was 80% at 60 days. High levels of LCDV, with a mean polymerase chain reaction (PCR) titre of 10⁶ PCR-U mg⁻¹ tissue, were detected in the fins and skin of LCD-affected fish at 20 °C, but were not detected in the spleen, kidney, brain and intestinal tissues of these fish. No LCD clinical signs were observed in the fish reared at 10 °C and 30 °C; however, a low level of LCDV (10³ PCR-U mg⁻¹ tissue) was detected in the fins and skin of these fish. By increasing the rearing temperature from 10 to 20 °C, lymphocystis clusters appeared on the skin and fins of the fish with no previous LCD clinical signs within 33 days after the temperature change. It was shown that permissive cells for LCDV infection exist in the epidermis of olive flounder. At low temperatures, small amounts of LCDV were able to persist over a period extended for a further 45 days in the fish epidermis, even though the fish showed no LCD clinical signs. The optimum growth temperature of LCDV is near 20 °C.     

Zn Uptake and Translocation in Rice Plants

Zinc (Zn) is an essential micronutrient with numerous cellular functions in plants, and its deficiency represents one of the most serious problems in human nutrition worldwide. Zn deficiency causes a decrease in plant growth and yield. On the other hand, Zn could be toxic if excess amounts are accumulated. Therefore, the uptake and transport of Zn must be strictly regulated. In this review, the dominant fluxes of Zn in soil?Croot?Cshoot translocation in rice plants (Oryza sativa) are described, including Zn uptake from soils in the form of Zn²⁺ and Zn-DMA at the root surface, and Zn translocation to shoots. Knowledge of these fluxes could be helpful to formulate genetic and physiologic strategies to address the widespread problem of Zn-limited crop growth.     

Enzymatic solubilization of collagen in the skin of diamond squid Thysanoteuthis rhombus: application of a fungal acid protease

Enzymatic solubilization of collagen from the skin tissue of diamond squid Thysanoteuthis rhombus, an underutilized resource in Japan, was attempted using an acid protease from the fungus Rhizopus niveus. This novel approach was compared with the conventional method using porcine pepsin. Both proteases were able to solubilize most of the skin collagen (>90 % of the total collagen) by performing the treatment in 0.5 M acetic acid at 4 °C for 72 h and at an enzyme/substrate ratio (w/w) of 1/10. The SDS-PAGE patterns of the solubilized collagen preparations were quite similar to each other, and two types of collagen (major and minor collagens) were purified from each preparation by cation-exchange column chromatography. These collagen types from the porcine pepsin-solubilized collagen showed similar features to those from the Rhizopus acid protease-solubilized collagen. These results suggest that the Rhizopus acid protease, a protease of non-animal origin, is applicable for solubilizing collagen in the skin of diamond squid.     

Bioenergy grass [Erianthus ravennae (L.) Beauv.] secretes two members of mugineic acid family phytosiderophores which involved in their tolerance to Fe deficiency

Ravenna grass, Erianthus ravennae (L.) Beauv. (E. ravennae) is a potential high biomass-energy crop with low input requirements. Iron (Fe) deficiency in calcareous soils is a widespread agronomic problem which reduces crop yields. Fe is sparingly soluble under aerobic conditions at high soil pH, such as in calcareous soils; therefore, plants cannot take up enough Fe. Increasing crop productivity of giant grasses, such as Ravenna grass in calcareous soil, has a positive effect by alleviating environmental problems. However, the growth character in calcareous soil and Fe homeostatic trait of Ravenna grass are largely unknown. In this study, we analyzed characteristics of Ravenna grass. The growth of E. ravennae plants were impaired in calcareous soil compared to those in the normal soil. In calcareous soil, the growth of E. ravennae plants differ among the water and fertilizer conditions; E. ravennae plants were grown better in the submerged condition adding micronutrient among conditions. These results suggested that impaired growth of E. ravennae in calcareous soil might be micronutrient shortage. We found that E. ravennae roots possess Fe reductase activities which were upregulated under Fe-deficient conditions. E. ravennae produced and secreted mugineic acid (MA) and deoxymugineic acid (DMA) to acquire Fe from the soil. The amount of MA was higher than that of DMA. Thus, E. ravennae might have both partial Strategy-I and Strategy-II Fe uptake systems. E. ravennae intercropped with transgenic rice plants producing and secreting MA through the introduction of the barley MA synthase gene showed improved growth compared to monocropped E. ravennae plants, suggesting that the increased amounts of MA enhanced their tolerance to Fe deficiency. Our results suggest that there is a considerable potential to improve the growth of E. ravennae plants in calcareous soils by enhancement of their Fe uptake systems through increase of MA production.     

Cloning of nicotianamine synthase genes from Arabidopsis thaliana

Nicotianamine synthase (NAS) catalyzes the trimerization of S-adenosylmethionine to form one molecule of nicotianamine (NA). NA is present in all the plants; it chelates metal cations, and is considered to play a role in metal homeostasis in plants. Moreover, in graminaceous monocotyledonous plants, NA is an essential intermediate in the biosynthesis of mugineic acid family phytosiderophores (MAs). In order to identify the gene encoding NAS in dicotyledonous plants, Arabidopsis thaliana databases were searched using the nucleotide sequence of the NAS gene from barley (HvNAS), which we have recently isolated. We found several ESTs and three genomic sequences highly homologous to HvNAS in the databases. Based on these nucleotide sequences and that of HvNAS, we designed 2 sets of primers to isolate the NAS orthologues in Arabidopsis and succeeded in obtaining three DNA clones encoding AtNAS (AtNAS1, 2, and 3). These clones were expressed in Escherichia coli and their protein products displayed the NAS activity. The expression of AtNASl was detected in both shoots and roots of A. thaliana by RT-PCR; AtNAS3 expression was only detected in the shoots. In contrast, AtNAS2 expression was not detected in any organs.     

Field tests of Poly(I:C) immunization with nervous necrosis virus (NNV) in sevenband grouper, Epinephelus septemfasciatus (Thunberg)

It was recently reported that Poly(I:C) immunization with live nervous necrosis virus (NNV) confers protection in sevenband grouper, Epinephelus septemfasciatus (Thunberg), from NNV infection. In the present study, we conducted field tests with sevenband grouper for the evaluation of Poly(I:C) immunization efficacy. In the first experiment, sevenband grouper were immunized with NNV followed by Poly(I:C) administration 7 weeks before natural occurrence of viral nervous necrosis (VNN). Survival rate of the naïve fish was 71.0%, whereas that of the immunized fish was 99.8%. In the second experiment, sevenband grouper were immunized 10 months before VNN occurrence and survival rate of the non‐treated and vaccinated fish was 79.5% and 97.5%, respectively. In the third experiment, we administered Poly(I:C) to sevenband grouper at 20 days after natural occurrence of VNN. The survival rate of the non‐treated fish was 9.8%, whereas that of fish administered Poly(I:C) was 93.7%. Based on these results, it was concluded that Poly(I:C) immunization conferred protection in fish against NNV infection in field tests and the protection lasted more than 10 months. Furthermore, even after occurrence of VNN, fish mortality could be reduced by Poly(I:C) administration and there was an unexpected curative effect on VNN‐affected fish.     

The effect of magmatic activity on hydrothermal venting along the superfast-spreading East pacific rise

A survey of hydrothermal activity along the superfast-spreading (approximately 150 millimeters per year) East Pacific Rise shows that hydrothermal plumes overlay approximately 60 percent of the ridge crest between 13 degrees 50' and 18 degrees 40'S, a plume abundance nearly twice that known from any other rige portion of comparable length. Plumes were most abundant where the axial cross section is inflated and an axial magma chamber is present. Plumes with high ratios of volatile ((3)He, CH(4), and H(2)S) to nonvolatile (Mn and Fe) species marked where hydrothermal circulation has been perturbed by recent magmatic activity. The high proportion of volatile-rich plumes observed implies that such episodes are more frequent here than on slower spreading ridges.     

Inoculation with N2-generating denitrifier strains mitigates N2O emission from agricultural soil fertilized with poultry manure

Pelleted poultry manure is recommended for use with agricultural soil as a replacement for chemical fertilizers; however, application of the manure stimulates nitrous oxide (N₂O) emission from the soil through denitrification. To mitigate the N₂O emission caused by application of pelleted poultry manure, soil microcosms were set up; each microcosm was inoculated with one of the following N₂-generating denitrifier strains previously been isolated from paddy soil: Azoarcus, Dyella, Dechloromonas, Niastella, and Burkholderia. When pelleted poultry manure was incubated on its own, N₂O was produced by denitrification. In contrast, N₂O emission was significantly lowered when the manure was inoculated with most of the N₂-generating strains. In soil microcosms, N₂O was emitted during incubation after application of the pelleted manure, while N₂O flux was significantly lowered when the soil was inoculated with Azoarcus sp. KS11B, Niastella sp. KS31B, or Burkholderia sp. TSO47-3 on the 12th day of incubation. In addition, when pelleted manure was inoculated with the strains prior to application in the soil microcosms, the level of N₂O emission was significantly lowered to ca. 40–60 % that from the non-inoculated control. Our study provides the prototype of a technique that uses microbial technology to mitigate N₂O emission from agricultural soil fertilized with pelleted poultry manure.     

Isolation of an algal morphogenesis inducer from a marine bacterium

Ulva and Enteromorpha are cosmopolitan and familiar marine algal genera. It is well known that these green macroalgae lose their natural morphology during short-term cultivation under aseptic conditions and during long-term cultivation in nutrient-added seawater and adopt an unusual form instead. These phenomena led to the belief that undefined morphogenetic factors that were indispensable to the foliaceous morphology of macroalgae exist throughout the oceans. We characterize a causative factor, named thallusin, isolated from an epiphytic marine bacterium. Thallusin induces normal germination and morphogenesis of green macroalgae.