Bacterial DNA activates immunity in <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis>

To initiate defense responses against invasion of pathogenic organisms, animals and plants must recognize microbe-associated molecular patterns (MAMPs). In this study, the elicitor activity of bacterial DNA on the model plant Arabidopsis thaliana was examined. EcoRI-digested plasmid DNA induced defense responses such as generation of reactive oxygen species and deposition of callose, whereas SmaI- and HapII-digested plasmid DNA and EcoRI-digested herring DNA did not remarkably induce these responses. Further, methylation of the CpG sequence of plasmid DNA and Escherichia coli DNA reduced the level of the defense responses. The endocytosis inhibitors wortmannin and amantadine significantly inhibited DNA-induced defense responses. These results suggest that non-methylated CpG DNA, as a MAMP, induced defense responses in Arabidopsis and that non-methylated DNA seems to be translocated into the cytoplasm by endocytosis.     

Stand-scale transpiration estimates in a Moso bamboo forest: II. Comparison with coniferous forests

In western Japan, Moso bamboo (Phyllostachys pubescens) forests have been expanding by replacing surrounding vegetation such as coniferous plantation forests and natural broadleaved forests. It has been speculated that the replacement of surrounding vegetation by bamboo forests could alter the vegetation water cycle and available water resources. We quantified stand-scale transpiration (E) in a bamboo forest on the basis of sap-flux measurements and compared the E value with values for coniferous forests. The annual E was estimated to be 567 mm. Seasonal trends in E primarily corresponded to seasonal trends in the vapor pressure deficit. Annual E for the bamboo forest was higher than that for the coniferous forests by 12% of annual precipitation (P). This difference in annual E is comparable with the difference in annual interception evaporation (I) relative to P between bamboo and coniferous forests; previous studies reported lower I for bamboo forests by ∼10% of P. Thus, the sum of E and I was comparable for bamboo and coniferous forests. As this study is the first measuring E of bamboo forests, further studies are required to examine the generality of our results.     

Laboratory observations on the vertical swimming behavior of Japanese common squid Todarodes pacificus paralarvae as they ascend into warm surface waters

This study examined the effect of warm temperature on the survival of paralarvae of Japanese common squid Todarodes pacificus and on their swimming behavior as they ascended to the surface. Observations were conducted on paralarvae in Petri dishes and in 85-cm-tall, cylindrical tanks that had a warmer upper layer and cooler lower layer separated by a small thermocline. Paralarvae were obtained through artificial fertilization and reared in Petri dishes at six experimental temperatures between 20.9 and 30.4 °C. Paralarvae reared at lower temperatures survived longer than those reared at warmer temperatures, and survival decreased at temperatures above 24 °C. When the mean temperatures in the upper layer of the tanks were 24.4–26.0 °C, the paralarvae ascended through the thermocline to the surface, but when the mean temperatures in the upper layer were 29.7–29.8 °C, paralarvae stopped ascending at the thermocline. These results show that paralarvae have a temperature preference but ascend to the surface in the unfavorable temperature range. The results suggest that increasing surface temperatures at spawning grounds will negatively affect both the survival and behavior of T. pacificus paralarvae.     

Purification and functional characterization of complement C3 and a novel zymosan-binding protein in tilapia serum

Zymosan, a yeast cell wall preparation that binds activated forms of complement C3, is a useful model target to activate the complement system. In our trial to analyze C3 diversity in Nile tilapia at the protein level using zymosan, we found that a novel 240-kDa serum protein (ZBP-240) also bound to zymosan in addition to C3-derived fragments. In the present study, we aimed to characterize tilapia C3 and ZBP-240, focusing on their immune-related functions. Four distinct C3 isoforms were purified from tilapia serum and shown to possess an intrachain thioester bond. ZBP-240 was also isolated from tilapia serum and examined for its binding properties to various microbial targets. As a result, ZBP-240 showed a wide spectrum of binding to Gram-positive and Gram-negative bacteria and yeasts. Amino acid sequence analysis of CNBr fragments of ZBP-240 suggested that this is a novel protein with no homologous sequence in protein databases. It was also suggested that the binding of ZBP-240 to microbes largely depends on hydrophobic interactions in a divalent-cation-independent manner, and that there may be a divalent-cation-dependent factor that enhances the binding of ZBP-240 in tilapia serum. Interestingly, ZBP-240 showed opsonic activity for tilapia kidney phagocytes at a level comparable to that of C3, implying that ZBP-240 is a novel teleost opsonic serum protein.     

Efficiency of planting hybrid larch F1 ( Larix gmelinii var. japonica × L. kaempferi ) at different planting densities and using seedlings or rooted cuttings

The efficiency of planting a hybrid larch F₁ at two planting densities and of using seedlings of hybrid larch F₁ or rooted cuttings of Gream, the registered variety, was investigated. Significantly more time was required to move from one planting spot to the next in plots with 625 seedlings/ha than in plots with 1,333 seedlings/ha, but there was no significant difference between seedlings and rooted cuttings. Approximately 18% more time was needed to plant a single planting stock at the low planting density than at the high density. The need to prune roots or enlarge a planting hole occurred more often for rooted cuttings than for seedlings, and 17% more time was needed to plant rooted cuttings of Gream than seedlings.     

Changes in daily rainfall characteristics in major rice producing provinces in Laos

In order to find the changes in rainfall characteristics and to examine the flood damage to lowland rice, a statistical analysis was carried out on the 40-year daily rainfall record at four rainfall stations (Thangon, Paksane, Seno, and Pakse) in Laos. The rainfall record was divided into two periods of 20 years each. The results of this analysis revealed the trends in changes regarding the frequency and the timing of the heavy daily rainfall events at the four stations. In Paksane in particular, heavy daily rainfall events tended to occur in the latter half of the rainy season.     

H2O2 production by copper amine oxidase, a component of the ecto-apyrase (ATPase)-containing protein complex(es) in the pea cell wall, is regulated by an elicitor and a suppressor from Mycosphaerella pinodes

Blue native PAGE analysis for cell wall proteins from pea epicotyls demonstrated that cell wall-associated ecto-apyrase (ATPase) formed a large protein complex(es) ranging from 450 to 900?kDa; one of the components of the complex was copper amine oxidase (CuAO), which catalyzes the oxidation of amines with the subsequent generation of ammonia and hydrogen peroxide. CuAO activity was coordinately regulated in vitro with ATP-hydrolyzing activity by an elicitor and a suppressor from Mycosphaerella pinodes. Moreover, treatment of cell wall proteins with the suppressor caused the appearance of the apyrase monomer. On the basis of these results, M. pinodes may target the apyrase-containing protein complex(es) of the host to attenuate cell wall-based, extracellular defense(s) including the production of hydrogen peroxide.     

Spatiotemporal analysis of pine wilt disease: Relationship between pinewood nematode distribution and defence response in Pinus thunbergii seedlings

Pine wilt disease is of major concern as it has destroyed pine forests in East Asia and Europe. Several studies have suggested that invasion by the pinewood nematode (PWN) Bursaphelenchus xylophilus, which causes this disease, evokes an excessive defence response in pine trees, resulting in tree death. However, few studies have quantitatively evaluated the correlation between PWN distribution and tree defence responses. Therefore, the present study aimed to quantify the number of PWNs and expression levels of putative pathogenesis‐related (PR) genes in different positions of Japanese black pine (Pinus thunbergii) seedlings over time. To quantify the number of PWNs in the seedlings, we used TaqMan quantitative real‐time PCR (qPCR) assay. During the early phase of infection, most PWNs were distributed around the inoculated sites, with only a small number being detected at distant sites, but the expression levels of PR genes were highly upregulated throughout the seedlings. Both the number of PWNs and expression levels of PR genes then increased drastically throughout the seedlings, all of which exhibited external symptoms. Thus, it appears that the rapid migration of PWNs induces a defence response throughout the seedling; however, this may not be effective in controlling these parasites, thereby ultimately leading to plant death.     

Incorporation of nitrogen from urea fertilizer into soil organic matter in rice paddy and cassava upland fields in Indonesia

Incorporation of newly-immobilized N into major soil organic matter fractions during a cropping period under paddy and upland cropping systems in the tropics was investigated in Jawa paddy fields with and without fish cultivation and a Sumatra cassava field in Indonesia. ¹⁵N-labelled urea (¹⁵N urea) was applied as basal fertilizer, and the soil samples were collected after harvest. The percentage of distribution of the residual N in soil from ¹⁵N urea into the humic acids, fulvic acid fraction, and humin were 13.1–13.9, 19.0–20.5, and 53.4–54.3%, respectively, for the Jawa paddy soils, and 14.9, 27.4, and 52.4%, respectively, for the Sumatra cassava soil. These values were comparable to the reported ones for other climatic zones. The percentage of distribution of ¹⁵N urea-derived N into humic acids was larger than that of total N into the same fraction in all the soils. The distribution into the fulvic acid fraction was also larger for ¹⁵N urea-derived N than for total N in the Jawa soils. Humic and non-humic substances in the fulvic acid fraction were separated using insoluble polyvinylpyrrolidone (PVP) into the adsorbed and non-adsorbed fractions, respectively. Less than 5% of the ¹⁵N urea-derived N in fulvic acid fraction was detected in the PVP-adsorbed fraction (generic fulvic acids). The proportion of non-hydrolyzable N remained after boiling with 6 M HCl in the ¹⁵N urea-derived N was 9.4–13.5%, 17.3–26.7%, and 8.4–16.6% for the humic acids, generic fulvic acids, and humin, respectively. The significantly low resistance to acid hydrolysis suggested that the ¹⁵N urea-derived N was less stable than the total N in soil regardless of the fractions of humus.     

Effect of forest structure on the spatial variation in soil respiration in a Bornean tropical rainforest

This study was undertaken to identify critical and practical factors explaining spatial variations in soil respiration and to estimate stand-scale soil respiration in an aseasonal tropical rainforest on Borneo Island. To this aim, we conducted soil respiration measurements at 25 points in a 40 m × 40 m subplot of a 4 ha study plot between 2002 and 2006, and examined the spatial variation in soil respiration averaged over the 4 years in relation to soil, root, and forest structural factors. In addition, we examined the spatial representativeness of soil respiration measured in the subplot using a specific scaling procedure. Consequently, we found significant positive correlation between the soil respiration and forest structural parameters such as the mean diameter at breast height (DBH), total basal area, and maximum DBH within 6 m of the measurement points. The most important factor was the mean DBH within 6 m of the measurement points, which had a significant linear relationship with soil respiration. Using the derived linear regression and an inventory dataset, we estimated the 4 ha plot-scale soil respiration. The 4 ha plot-scale estimation (6.0 μmol m⁻² s⁻¹) was nearly identical to the subplot-scale measurements (5.7 μmol m⁻² s⁻¹), which were roughly comparable to the nocturnal CO₂ fluxes calculated using the eddy covariance technique. In addition, we discuss characteristics of the stand-scale soil respiration at this site by comparing with those of other forests reported in previous literature in terms of the soil C balance. Soil respiration at our site was noticeably greater, relative to the incident litterfall amount, than soil respiration in other tropical and temperate forests probably owing to the larger total belowground C allocation by emergent trees. Overall, this study suggests the arrangement of emergent trees with larger DBH and their belowground C allocation could be primary factors controlling spatial variations in soil respiration in the tropical rainforest.