Search

Jasmonic acid (JA) plays an important role in the induction of herbivore resistance in many plants. However, JA-independent herbivore resistance has been suggested. An herbivore-resistance-inducing substance was isolated from Tobacco mosaic virus-infected tobacco (Nicotiana tabacum) leaves in which a hypersensitive response (HR) was induced and identified as loliolide, which has been identified as a β-carotene metabolite. When applied to tomato (Solanum lycopersicum) leaves, loliolide decreased the survival rate of the two-spotted spider mite, Tetranychus urticae, egg deposition by the same pest, and the survival rate of larvae of the common cutworm Spodoptera litura without exhibiting toxicity against these herbivores. Endogenous loliolide levels increased not only with an infestation by S. litura larvae, but also with the exogenous application of their oral secretions in tomato. A microarray analysis identified cell-wall–associated defense genes as loliolide-responsive tomato genes, and exogenous JA application did not induce the expression of these genes. Suppressor of zeaxanthin-less (szl), an Arabidopsis (Arabidopsis thaliana) mutant with a point mutation in a key gene of the β-carotene metabolic pathway, exhibited the decreased accumulation of endogenous loliolide and increased susceptibility to infestation by the western flower thrip (Frankliniella occidentalis). A pretreatment with loliolide decreased susceptibility to thrips in the JA-insensitive Arabidopsis mutant coronatine-insensitive1. Exogenous loliolide did not restore reduced electrolyte leakage in szl in response to a HR-inducing bacterial strain. These results suggest that loliolide functions as an endogenous signal that mediates defense responses to herbivores, possibly independently of JA, at least in tomato and Arabidopsis plants.

Californian populations of Echinochloa phyllopogon have evolved multiple-herbicide resistance (MHR), posing a threat to rice production in California. Previously, we identified two CYP81A cytochrome P450 genes whose overexpression is associated with resistance to acetolactate synthase (ALS) inhibitors from two chemical groups. Resistance mechanisms to other herbicides remain unknown. We analyzed the sensitivity of an MHR line to acetyl-CoA carboxylase (ACCase) inhibitors from three chemical groups, followed by an analysis of herbicide metabolism and segregation of resistance of the progenies in sensitive (S) and MHR lines. ACCase herbicide metabolizing function was investigated in the two previously identified P450s. MHR plants exhibited resistance to all the ACCase inhibitors by enhanced herbicide metabolism. Resistance to the ACCase inhibitors segregated in a 3 : 1 ratio in the F2 generation and completely co-segregated with ALS inhibitor resistance in F6 lines. Expression of the respective P450 genes conferred resistance to the three herbicides in rice, which is in line with the detection of hydroxylated herbicide metabolites in vivo in transformed yeast. CYP81As are super P450s that metabolize multiple herbicides from five chemical classes, and concurrent overexpression of the P450s induces metabolism-based resistance to the three ACCase inhibitors in MHR E. phyllopogon, as it does to ALS inhibitors.

Arsenic species, including arsenous acid, arsenic acid, methylarsonic acid, and dimethylarsinic acid, were determined using HPLC-ICPMS. The species were separated with a Discovery HS F5 column and a simple, volatile, and isocratic mobile phase of 0.1% (v/v) formic acid and 1% (v/v) methanol. The Discovery HS F5 column with a pentafluorophenyl (PFP) stationary phase gave sharp peaks and full separation of the arsenic species in 5min, and other PFP columns showed lower performance. This separation method was applied to arsenic species analysis in rice. The extraction of arsenic from rice samples was performed using 0.15M nitric acid. The methodology was validated by use of certified reference materials, NMIJ CRM 7503-a and NIST SRM 1568a, and extremely low arsenic rice samples as blank samples.

SummaryBeekeepers in Japan have been finding as many as 1,000 dead honey bees piled up in front of hive entrances. They have observed that these mass bee deaths tend to occur at about the same time as measures are taken to control rice bugs, which appear every year during the summer in rice-producing districts. We set up and conducted controlled field studies from July to August in 2012 in a rice-producing district of northern Japan where frequent mass bee deaths are observed each summer. As had occurred in the area in previous years, and as we directly observed during our field investigations, masses of honey bees were found dead at the entrance to their hives. Samples of pollen and honey bee corpses were found to contain measurable concentrations of five active ingredients of insecticides: clothianidin, dinotefuran, ethiprole, etofenprox, and phenthoate. Insecticides containing these active ingredients are known to have been used for rice bug control in this area. Furthermore, we did not observe other k...

Deoxynivalenol (DON) is a natural toxin of fungi that cause Fusarium head blight disease of wheat and other small-grain cereals. DON accumulates in infected grains and promotes the spread of the infection on wheat, posing serious problems to grain production. The elucidation of DON-catabolic genes and enzymes in DON-degrading microbes will provide new approaches to decrease DON contamination. Here, we report a cytochrome P450 system capable of catabolizing DON in Sphingomonas sp. strain KSM1, a DON-utilizing bacterium newly isolated from lake water. The P450 gene ddnA was cloned through an activity-based screening of a KSM1 genomic library. The genes of its redox partner candidates (flavin adenine dinucleotide [FAD]-dependent ferredoxin reductase and mitochondrial-type [2Fe-2S] ferredoxin) were not found adjacent to ddnA ; the redox partner candidates were further cloned separately based on conserved motifs. The DON-catabolic activity was reconstituted in vitro in an electron transfer chain comprising the three enzymes and NADH, with a catalytic efficiency ( k cat / K m ) of 6.4 mM −1 s −1 . The reaction product was identified as 16-hydroxy-deoxynivalenol. A bioassay using wheat seedlings revealed that the hydroxylation dramatically reduced the toxicity of DON to wheat. The enzyme system showed similar catalytic efficiencies toward nivalenol and 3-acetyl deoxynivalenol, toxins that frequently cooccur with DON. These findings identify an enzyme system that catabolizes DON, leading to reduced phytotoxicity to wheat.

In a study to elucidate the possible involvement of phytoalexins in acibenzolar-S-methyl (ASM)-induced systemic resistance in cucumber plants (Cucumis sativus L.), the phenolic compounds were extracted from ASM-treated and inoculated plants and compared with those from Milsana®-treated plants previously reported to accumulate phytoalexins in cucumber. The glycoside-linked phenolic compounds from cucumber leaves were tested for their antifungal activity to the growth of pathogens which were most effective against the cucumber anthracnose fungus Colletotrichum orbiculare, followed by the scab fungus Cladosporium cucumerinum but ineffective against the Corynespora leaf spot fungus Corynespora cassiicola. Nevertheless, the accumulations of active compounds appeared to increase with the growth stages of cucumber plants irrespective of ASM treatment. In ASM-pretreated cucumber plants either inoculated with anthracnose or the powdery mildew fungus, there was no increase in phytoalexin-like phenolics.

The objective of this study was to clarify the adsorption and desorption characteristics of several herbicides in sediment. Five herbicides, esprocarb, thiobencarb, dimethametryn, pretilachlor, and simetryn were examined in this study. The adsorption ratio on the sediment increased in the following order: pretilachlor < dimethametryn < simetryn < thiobencarb < esprocarb. On the other hand, the adsorption ratio on the sediment without organic matter increased in the following order: thiobencarb < esprocarb < pretilachlor < dimethametryn < simetryn. Furthermore, the amounts of simetryn, dimethametryn, and pretilachlor adsorbed on the sediment without organic matter increased, while those of esprocarb and thiobencarb decreased in comparison to the original sediment. These results strongly suggested that the mineral surface in the sediment was very important as the adsorption site for the herbicide, especially in the case of simetryn, dimethametryn, and pretilachlor. All the adsorption and desorption data fitted well with the Freundlich equation. The hysteresis in the adsorption-desorption phenomena in the sediment was observed for all the herbicides, and it was affected by the organic matter in sediment, especially in the case of dimethametryn and pretilachlor.

The aquatic crustacean Daphnia magna is an important species for ecotoxicological study, and is often used as a test organism for environmental risk assessment. However, the mechanism of xenobiotic metabolism by this species has not been studied in detail. In the present study, pyrene was used as model substance to investigate the mechanism of xenobiotic metabolism in D. magna. The results of 24-h exposure experiments showed that D. magna could metabolize pyrene and biotransform it into water-soluble metabolites. On the other hand, the metabolism of pyrene was significantly inhibited by SKF-525A as the cytochrome P450 (CYP) inhibitor. These observations indicated that oxidation by CYP participated in the biotransformation of pyrene by D. magna. We also identified the pyrene metabolites formed by D. magna by HPLC with an electrospray ionization triple quadrupole mass spectrometry detector (LC/ESIMS/MS) and de-conjugation by sulfatase, beta-glucuronidase, and beta-glucosidase. One of the metabolites was ionized in ESI negative mode and formed a dominant mass of m/z 297 (MS) with the product ion of m/z 217 (MS2). Furthermore, this metabolite formed 1-hydroxypyrene on treatment with sulfatase. This metabolite was considered to be a sulfate conjugate of oxidized pyrene (1-hydroxypyrenesulfate). Furthermore, we quantified the deconjugated 1-hydroxypyrene formed by the above enzyme treatment. It showed that 52% of the total metabolized pyrene was biotransformed into 1-hydroxypyrene-sulfate, and more than 73% was biotransformed into oxidized pyrene conjugate. These results indicated that CYP and several conjugation enzymes participate in its biotransformation, and sulfation is important in D. magna for metabolism and elimination of xenobiotics.

In order to determine if differences in timing or levels of gene and enzyme activations were likely to account for differences in resistance of pear cultivars against Japanese pear scab, time course analyses of several potential defense genes and enzymes as well as salicylic acid (SA) accumulation were carried out using leaf tissue of susceptible Japanese pear cv. ‘Kousui’ and resistant pear cvs. ‘Kinchaku’, ‘Mamenashi 12’ and ‘Flemish Beauty’ upon inoculation with the race 1 of Venturia nashicola. A phenylalanine-ammonia lyase gene (pal) expression was not significantly affected by pathogen regardless of the compatible or incompatible interaction. Accumulation of pathogenesis-related protein 1 (pr1) and chitinase (chi) transcripts was early and highly elicited in the host resistant cv. ‘Kinchaku’, while in the other interactions it was delayed. In general, enhancement of SA accumulation and increase in the expression of pr1 gene in ‘Kinchaku’ are positively correlated, suggesting that this resistance is SA-dependent. The activity of four antioxidant enzymes (superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and guaiacol peroxidase (GPX)) was significantly enhanced only in resistant cultivars with a differential pattern of induction according to the cultivar. Superoxide anion ( O 2 ˙− ) was highly detected in inoculated leaves of the resistant cvs. ‘Kinchaku’ and ‘Mamenashi 12’ when compared to the susceptible cv. ‘Kousui’. The involvement of the oxidative burst as well as its relationship with the activity of the antioxidant enzymes and with resistance is discussed.

The effects of herbicide (mefenacet and pretilachlor) applications on soil microbial communities in rice paddy soil were investigated in a laboratory study using phospholipid fatty acid (PLFA) profiles. Soils with or without herbicide application were incubated separately under oxidative or reductive conditions for 30 d. Half-life (DT50) of mefenacet was 14 d under oxidative conditions and 9.8 d under reductive conditions. DT50 of pretilachlor was 17 d under oxidative conditions and 8.8 d under reductive conditions. PLFA contents did not seem to be affected by the residual levels of herbicides. The composition of PLFAs under in both the oxidative and reductive conditions fluctuated during the incubation period. However, the effects of applications of herbicides (mefenacet and pretilachlor) under oxidative and reductive conditions in rice paddy soil did not affect appreciably the soil microbial biomass and the structure of the soil microbial communities, as determined by PLFA profiles. Fluctuation...

We have isolated a new recessive dwarf mutant of rice (Oryza sativa L. cv Nipponbare). Under normal growth conditions, the mutant has very short leaf sheaths; has short, curled, and frizzled leaf blades; has few tillers; and is sterile. Longitudinal sections of the leaf sheaths revealed that the cell length along the longitudinal axis is reduced, which explains the short leaf sheaths. Transverse sections of the leaf blades revealed enlargement of the motor cells along the dorsal-ventral axis, which explains the curled and frizzled leaf blades. In addition, the number of crown roots was smaller and the growth of branch roots was weaker than those in the wild-type plant. Because exogenously supplied brassinolide considerably restored the normal phenotypes, we designated the mutantbrassinosteroid-dependent 1(brd1). Further, under darkness, brd1showed constitutive photomorphogenesis. Quantitative analyses of endogenous sterols and brassinosteroids (BRs) indicated that BR-6-oxidase, a BR biosynthesis enzyme, would be defective. In fact, a 0.2-kb deletion was detected in the genomic region ofOsBR6ox (a rice BR-6-oxidase gene) in thebrd1 mutant. These results indicate that BRs are involved in many morphological and physiological processes in rice, including the elongation and unrolling of leaves, development of tillers, skotomorphogenesis, root differentiation, and reproductive growth, and that the defect of BR-6-oxidase caused thebrd1 phenotype.

We present evidence that the rice receptor for N-acetylchitooligosaccharide elicitor does not couple to heterotrimeric G-protein (G-protein), one of the most important signal transducers from the cell surface to down-stream effectors in various cellular responses of many organisms. Using mutant rice cells lacking functional G-protein α-subunit, cellular responses of suspension-cultured rice cells derived from Daikoku dwarf (d1) mutants that were shown to contain mutations in the coding region of the G-protein α-subunit (Fujisawa et al. 1999) to N-acetylchitooligosaccharide (oligochitin) elicitor were compared with those of the corresponding parent cell lines. All the elicitor-induced cellular responses, such as medium alkalinization, generation of reactive oxygen species, expression of early responsive genes, PAL and PR genes, and production of phytoalexin, were basically identical in the mutant and wild type cell lines. Considering the reported presence of a single copy gene for the G-protein α-subunit in many plant species including rice, these results strongly support the above conclusion.

Streptomyces coelicolor A3(2) strain M145 has eight chitinase genes scattered on the chromosome: six genes for family 18 (chiA, B, C, D, E and H) and two for family 19 (chiF and G). In this study, the expression and regulation of these genes were investigated. The transcription of five of the genes (chiA, B, C, D and F) was induced in the presence of colloidal chitin while that of the other three genes (chiE, G and H) was not. The transcripts of the five induced chi genes increased and reached their maximum at 4 h after the addition of colloidal chitin, all showing the same temporal patterns. The induced levels of the transcripts of chiB were significantly lower than those of the other four genes. Dynamic analysis of the transcripts of the chi genes indicated that chiA and chiC were induced more strongly than chiD and chiF. Addition of chitobiose also induced transcription of the chi genes, but significantly earlier than did colloidal chitin. When cells were cultured in the presence of colloidal chitin, an exponential increase of chitobiose concentration in the culture supernatant was observed prior to the induced transcription of the chi genes. This result, together with the immediate effect of chitobiose on the induction, suggests that chitobiose produced from colloidal chitin is involved in the induction of transcription of the chi genes. The transcription of the five chi genes was repressed by glucose. This repression was apparently mediated by the glucose kinase gene glkA.

Field trials were conducted at the National Institute of Agro-Environmental Sciences experiment station from 1995 to 1997. Each trial was carried out from mid-May to early July every year. Determining the pattern and rate of dissipation of pretilachlor and mefenacet in paddy soil at three different depths (0-1, 1-5 and 5-10 cm) and in paddy water was the primary objective of the experiments. Half-lives (DT 50 ) of the herbicides were calculated using both the simple first order kinetics (SFOK) and the biphasic first order kinetics (BFOK). The pattern and rate of dissipation of pretilachlor in both soil and water were quite different from that of mefenacet. At the 0-1 cm soil layer (oxidative), dissipation of pretilachlor was quite rapid during the first 3 weeks but slowed down afterwards. In case of mefenacet, dissipation was a steady decline until the last sampling day. The DT 50 in this layer was between 9 to1 1 days and 7 tolO days for mefenacet and pretilachlor, respectively. At the lower soil layers (1-5 and 5-10 cm; reductive) pretilachlor appeared to leach from the upper layer within the first two weeks and then quickly disappeared after wards. Faster degradation of pretilachlor was noted in these reductive soil layers. On the other hand, mefenacet dissipation declined steadily at these layers. Also, leaching of mefenacet was not as evident as in pretilachlor. Mefenacet concentration in paddy water peaked over the second to third day and its dissipation was rapid until the fourth week. Dissipation pattern of pretilachlor was a steady curvilinear decline. In paddy water, DT 50 was about 3.3 to 4.1 1 days for mefenacet and 3.0 to 3.6 days for pretilachlor. Calculating the half-life In soil (0-1 cm layer) using SFOK appears sufficient for mefenacet while a more complex model such as the BFOK describes that of pretilachlor better. The half-life and dissipation pattern of both herbicides did not vary considerably across years. There was no evidence of residue build-up due to continuous application of the herbicides in the same plots.

A silkworm (Bombyx mori) proteome database (SPD) was constructed using Make-2DDB II software. The present SPD contains the proteomes of the seven major tissues in the silkworm: the middle silkglands, posterior silkglands, midguts, fat bodies, hemolymph, ovaries, and Malpighian tubules. Proteins in each tissue at day 3 of the fifth instar were identified by MS/MS analysis and the protein profiles by 2-DE from day 1 of the fourth instar larva to the adult moth were constructed.

Lolitrems are neurotoxins found in endophyte-infected perennial ryegrass. Lolitrems, primarily lolitrem B, are the causative agents of ryegrass staggers in livestock. To guarantee the safety of meat produced from cattle consuming endophyte-infected perennial ryegrass, lolitrem B concentrations in tissues of Japanese Black cattle were determined using high-performance liquid chromatography. Lolitrem B was not detected in muscle, liver, kidney, or cerebrum of a Japanese Black cow with signs of ryegrass staggers. In contrast, perirenal fat contained 210 ppb lolitrem B. Three cows that received half as much perennial ryegrass straw as the cow with ryegrass staggers showed no clinical signs of ryegrass staggers. However, low concentrations of lolitrem B (less than 150 ppb) were detected in their fat tissue. These observations indicate that human exposure to the neurotoxic effect of lolitrem B through beef is unlikely. The amount of lolitrem B consumed by cattle can be estimated by the determination of lolitrem B in fat tissue.

Environmental contextRice is a major human dietary source of arsenic. We identified a novel organoarsenic species, arsinothricin, produced by a bacterium in the rice rhizosphere. This result suggests diverse biochemical dynamics and microbial biodiversity of arsenic metabolism in the rice rhizosphere. AbstractMethylated arsenic compounds in rice grains originate from the action of soil bacteria in the rice rhizosphere. Here, we investigated the chemical structures of arsenic compounds produced by a bacterium, Burkholderia gladioli strain GSRB05, in the rice rhizosphere. When cultured in liquid R2A medium containing arsenite (AsIII), strain GSRB05 produced two unknown novel arsenic compounds that were later identified as arsinothricin (AST, 2-amino-4-(hydroxymethylarsinoyl)butanoic acid), an arsenic mimetic of the herbicide phosphinothricin, and a probable hydroxyl precursor of AST, termed AST-OH (2-amino-4-(dihydroxyarsonoyl)butanoic acid). The chemical structure of AST was determined by means of liquid chromatography–high-resolution tandem mass spectrometry and NMR analyses, whereas that of AST-OH was estimated by means of ultra-high-performance liquid chromatography–tandem mass spectrometry. Time-dependent AsIII transformation by strain GSRB05 showed that AST was produced after AST-OH. Compared with AsIII, AST showed higher absorption by, and was more toxic to, Escherichia coli DH5α cells in M9 minimal medium, which lacks amino acids. These findings have implications for the environmental transfer of arsenic, and human health consequences in terms of our dietary burden of arsenic.

The mycotoxin deoxynivalenol (DON), a secondary metabolite produced by species of the plant pathogen Fusarium, causes serious problems in cereal crop production because of its toxicity towards humans and livestock. A biological approach for the degradation of DON using a DON-degrading bacterium (DDB) appears to be promising, although information about DDBs is limited. We isolated 13 aerobic DDBs from a variety of environmental samples, including field soils and wheat leaves. Of these 13 strains, nine belonged to the Gram-positive genus Nocardioides and other four to the Gram-negative genus Devosia. The degradation phenotypes of the two Gram types were clearly different; all washed cells of the 13 strains degraded 100 μg mL(-1) DON to below the detection limit (0.5 μg mL(-1)), but the conditions inducing the DON-degrading activities differed between the two Gram types. The HPLC profiles of the DON metabolites were also distinct between the two genera, although all strains produced 3-epi-deoxynivalenol. The Gram-positive strains showed DON assimilation in media containing DON as a carbon source, whereas the Gram-negatives did not. Our results suggest that aerobic DDBs are distributed within at least two phylogenetically restricted genera, suggesting independent evolution of the DON-degradation mechanisms.

Homocitrate is a component of the iron-molybdenum cofactor in nitrogenase, where nitrogen fixation occurs. NifV, which encodes homocitrate synthase (HCS), has been identified from various diazotrophs but is not present in most rhizobial species that perform efficient nitrogen fixation only in symbiotic association with legumes. Here we show that the FEN1 gene of a model legume, Lotus japonicus, overcomes the lack of NifV in rhizobia for symbiotic nitrogen fixation. A Fix(-) (non-fixing) plant mutant, fen1, forms morphologically normal but ineffective nodules. The causal gene, FEN1, was shown to encode HCS by its ability to complement a HCS-defective mutant of Saccharomyces cerevisiae. Homocitrate was present abundantly in wild-type nodules but was absent from ineffective fen1 nodules. Inoculation with Mesorhizobium loti carrying FEN1 or Azotobacter vinelandii NifV rescued the defect in nitrogen-fixing activity of the fen1 nodules. Exogenous supply of homocitrate also recovered the nitrogen-fixing activity of the fen1 nodules through de novo nitrogenase synthesis in the rhizobial bacteroids. These results indicate that homocitrate derived from the host plant cells is essential for the efficient and continuing synthesis of the nitrogenase system in endosymbionts, and thus provide a molecular basis for the complementary and indispensable partnership between legumes and rhizobia in symbiotic nitrogen fixation.

This study reports the mode of action of acibenzolar-S-methyl (ASM) against Japanese pear scab, caused by Venturia nashicola. Pretreatment of potted Japanese pear trees with ASM reduced scab symptoms and potentiated several lines of plant defense response. This included transcripts encoding polygalacturonase-inhibiting protein (PGIP) that were highly and transiently promoted after scab inoculation of plants pretreated with ASM, suggesting a possible role for defenses involved in direct interaction with the pathogen. The activity of the key enzyme of phenylpropanoid pathway, phenylalanine ammonia lyase (PAL), was enhanced in scab-inoculated leaves pretreated with ASM only 7 days after inoculation, suggesting that it may play a minor role in induced resistance. In this work, salicylic acid (SA) accumulation was enhanced in ASM-treated leaves for the first time, according to an equivalent time course to that of PAL activity. However, a delayed induction of SA accumulation in ASM-treated leaves compared with kinetics of induction of several pathogenesis- related (PR) proteins or their encoding genes suggested that resistance triggered by ASM may be SA-independent. Among these PR proteins, PR-1, chitinase and PR-10 were promoted early by ASM after scab inoculation. Peroxidase, as well as enzymes involved in the oxidative burst such as superoxide dismutase, catalase, and ascorbate peroxidase were weakly activated with ASM treatment alone or pathogen inoculation alone and highly enhanced in ASM pretreated plants upon challenge inoculation, suggesting the occurrence of priming phenomenon during the interaction of Japanese pear-ASM-V. nashicola. An early potentiation of the activity of these enzymes after scab inoculation of leaves pretreated with ASM suggested that active oxygen species may be involved as a signal for the activation of PR proteins or genes.

Diphenylarsinic acid, phenylarsonic acid, methylphenylarsinic acid (MPAA), dimethylphenylarsine oxide (DMPAO), and methyldiphenylarsine oxide (MDPAO) in soil and rice were extracted, separated by reversed-phase chromatography, and quantified by ICPMS with a membrane desolvating system. For the extraction of arsenicals from rice grain and straw, 68% HNO3 provided better extraction efficiency than water, 50% methanol, or 2.0 mol L(-1) trifluoroacetic acid. For the extraction from soil, 68% HNO3 provided better extraction efficiency than H2O, 1 mol L(-1) H3PO4, or 1 mol L(-1) NaOH. The contaminated soil contained all five aromatic arsenicals along with inorganic arsenicals as main species (5.86 +/- 0.19 microg of As kg(-1): 60.8 +/- 2.0% of total extracted As). After pot experiments, rice straw contained mainly DMPAO (7.71 +/- 0.48 microg of As kg(-1): 60.5 +/- 3.7%), MDPAO (0.91 +/- 0.07 microg of As kg(-1): 7.2 +/- 0.5%), and inorganic As (2.85 +/- 0.20 microg of As kg(-1): 22.3 +/- 1.6%). On the other hand, rice grain contained mainly MPAA (1.17 +/- 0.04 microg of As kg(-1): 86.7 +/- 2.7%). The root uptake of each species from the soil and transport from straw to grains were significantly related to the calculated log K(ow) values.

4種の芳香族塩素化合物, ヘキサクロロベンゼン, ペンタクロロフェノール, デカクロロビフェニルおよびオクタクロロダイベンゾフランのヘキサンあるいはジオキサン溶液について, キセノンランプ照射により光分解特性である量子収量 (φλ) を求めた. これら芳香族塩素化合物の波長313nmにおける量子収量として, それぞれ1.538×10-1, 6.733×10-1, 4.113×10-1および2.259×10-2モル/アインシュタインの値を得た. これら量子収量と文献記載の太陽光エネルギー強度から, 北緯40度の水表面における光分解速度定数と半減期を推定した.

The cholinesterase (ChE)-inhibiting activity of water and the concentrations of representative inhibitors were monitored in the Tone canal, Japan, during April to December 2006. The ChE-inhibiting activity, measured by using horse serum as enzyme source, increased from late April to early June, and from September to October. Although the trends in the ChE-inhibiting activity of the samples were consistent with concentration changes of organophosphorus pesticides, ChE-inhibiting activity was not observed in samples replicated on the basis of the chemical concentrations detected. The water samples were treated with chlorine to enhance the ChE-inhibiting activity by conversion of thiophosphate pesticides to phosphate pesticides. The ChE-inhibiting activity increased in almost all the chlorine-treated samples, although organophosphorus pesticides were either not detected or detected in traces in the samples by gas chromatographic–mass spectrometric analysis. These results suggested that assay of ChE-inhibiting activity is important for evaluating the ecotoxicity of environmental water, because toxicological investigations based solely on inhibitor concentrations may underestimate the contamination. Furthermore, the combined method of oxidation by chlorination and the ChE assay is very effective for screening and monitoring of organophosphorus pesticides in environmental water.

We found that aquatic crustaceans, decapoda; atyidae (Caridina multidentata, Neocaridina denticulate, and Paratya compressa), metabolize pyrene to a new conjugation product. The results of deconjugation treatments indicated that glucose and sulfate combined with 1-hydroxypyrene. Further analysis by LC/ESI-MS/MS showed that the molecular weight of the product was 460 (m/z 459; deprotonated ion), and that it has a glucose-sulfate moiety (m/z 241; fragment ion). These results indicated that the new metabolite was the glucose-sulfate conjugate of 1-hydroxypyrene. The glucose-sulfate conjugate is a phase II product that has not been reported previously from any organism. Several studies have demonstrated that sulfation is an important pathway for metabolism of xenobiotics in aquatic invertebrates. Thus, glucose-sulfate conjugates may add an important signal for excretion or sequestration of xenobiotics for aquatic invertebrates.

This work describes the analytical performance of the enzyme-linked immunosorbent assay (ELISA) for the fungicide chlorothalonil to effectively exploit as a simple and rapid detection system for pesticide residue on the scenes of the agricultural production and distribution. This ELISA represents the satisfactory analytical characteristics (I50 value, 0.34 ng/g; limit of detection, 0.052 ng/g) to detect chlorothalonil at the regulatory values or thereabout in a sample. Noticeable cross-reactivities were shown with two fungicides, fthalide (58.8%) and pentachloronitrobenzene (quintozene) (20.0%), and some non-agrochemicals such as tetrachloroterephthalonitrile (96.8%) and tetrachlorophthalonitrile (68.3%). The influence of three organic solvents (methanol, acetone, and acetonitrile) used as extractants for chlorothalonil residue was evaluated, with the result that methanol was the most suitable solvent for the ELISA, and the final concentration in the well could be up to 5% (v/v) without any negative influence on the ELISA. It has been possible to directly analyze chlorothalonil residue only by giving dilution of each sample extract with water prior to the ELISA analysis. The average recovery values from the spiked samples by the ELISA were between 101.7 and 113.6% with the average coefficients of variation between 2.6 and 5.9%. Although the results obtained from the ELISA correlated well with those from the reference GC/MS methods for all agricultural samples (r > 0.98), the linear function inclined to the ELISA results because of loss during complex sample preparations for GC/MS analysis. Nevertheless, the results demonstrated that the proposed ELISA is a reliable, cost-effective, and rapid quantitative method for chlorothalonil residue.

Direct determination of cadmium in rice flour by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is described. This superior quantitative method needs no conventional laborious sample pretreatment such as decomposition and extraction. To construct the calibration line and estimate the detection limit, three certified reference materials for rice flour, NIES nos. 10a, 10b and 10c, were used and contaminated with three different concentrations of cadmium (0.023, 0.32 and 1.82 mg kg−1, respectively). These three kinds of rice flour were finely ground and pressed into disks for analysis. The calibration line showed good linearity in the range 0.023–1.82 mg kg−1. The determination did not require internal standardization and no significant interference was observed.