Hwang-Ju Jeon

Integrated biomarkers induced by chlorpyrifos in two different life stages of zebrafish (Danio rerio) for environmental risk assessment.

This study was performed to understand how chlorpyrifos (CHL) affects zebrafish (Danio rerio) embryos and adults, by exposing this model organism to various concentrations of the insecticide. The 96-h acute toxicity test to determine the effect of CHL on adult zebrafish yielded a LC50 of 709.43μg/L(-1). Small molecular weight proteins less than 25kDa and phospholipids were analyzed with MALDI-TOF MS/MS in order to compare expression patterns, revealing that some peaks were dramatically altered after CHL treatment. Whereas no acute toxicity was detected in the embryo toxicity test, malformation of zebrafish larvae was observed, with many individuals harboring curved spines. In an angiogenesis test on larvae of transgenic zebrafish, CHL did not have an inhibitory effect. Relative gene expression analyses using real-time polymerase chain reaction (RT-PCR) of DNA from zebrafish embryos revealed that different subtypes of cytochrome P450 (CYP450), such as CYP1A and CYP3A, were significantly up-regulated in response to CHL at a concentration of 400μg/L(-1) compared to the control. The expression level of NR1I2, a CYP gene transcriptional regulator, UGT1a1, and MDR1 were all up-regulated in the CHL-treated embryos. Finally, the expression level of acetylcholinesterase (AChE) and catalase (CAT) decreased, whereas that of superoxide dismutase (SOD) did not differ significantly. Our results suggest that the up-regulation of metabolic enzymes including CYP450 and MDR1 may be involved in CHL resistance in zebrafish.

Acute toxicity and gene responses induced by endosulfan in zebrafish (Danio rerio) embryos

Abstract Endosulfan has been listed as a persistent organic pollutant, and is frequently found in agricultural environments during monitoring processes owing to its heavy use and persistent characteristics. This study was conducted to understand the effects of endosulfan on the development of zebrafish (Danio rerio) embryos by exposing them to a specific range of endosulfan concentrations. Exposing zebrafish embryos to endosulfan for 96 h yielded no acute toxicity until the concentration reached 1500 μg L−1, whereas malformed zebrafish larvae developed severely curved spines and shortened tails. About 50% of zebrafish larvae were malformed when exposed to 600 μg L−1 of endosulfan. Comparative gene expression using real-time quantitative polymerase chain reaction was assessed using endosulfan-exposed zebrafish embryos. CYP1A and CYP3A were significantly enhanced in response to endosulfan treatment. Two genes, acacb and fasn, encoding acetyl-CoA carboxylase b and fatty acid synthase proteins, respectively, were also up-regulated after treating zebrafish embryos with endosulfan. These genes are also involved in fatty acid biosynthesis. The genes encoding vitellogenin and Hsp70 increased in a concentration-dependent manner in embryos. Finally, biochemical studies showed that acetylcholinesterase activity was reduced, whereas glutathione S-transferase and carboxylesterase activities were enhanced in zebrafish embryos after endosulfan treatment. These biochemical and molecular biological differences might be used for tools to determine contamination of endosulfan in the aquatic environment.

Highly selective biomarkers for pesticides developed in Eisenia fetida using SELDI-TOF MS

The repeated use of pesticides, and their subsequent residues, has contributed to severe adverse effects on the environment, including risks to human health. Therefore, it is important to assess the quality of the environment to ensure it remains free from pesticide residues. The six pesticides tested in this study showed high mortality on Eisenia fetida with LC50 values ranging from 7.7 to 37.9 g L(-1). The strongest lethal effect resulted from the organochlorine insecticide endosulfan (LC50=7.7 g L(-1)). Following exposure to the carbamate pesticides, acetylcholinesterase activity in E. fetida decreased dramatically in comparison to the control. Carboxylesterase activity was only lowered in E. fetida exposed to propoxur, when compared to the control. The remaining five pesticides had no significant effect on carboxylesterase activity in E. fetida. In order to discover pesticide-specific biomarkers with differentially expressed proteins after exposure to pesticides, protein patterns of pesticide-treated E. fetida were analyzed using SELDI-TOF MS with Q10 ProteinChips. Protein patterns were compared with their intensities at the same mass-to-charge ratios (m/z). All 42 peaks had intensities with associated p-values less than 0.089, and 40 of these peaks had associated p-values of 0.05. Using SELDI-TOF MS technology, selective biomarkers for the six pesticides tested were found in E. fetida; four proteins with 5425, 5697, 9523, and 9868 m/z were consistently observed in the earthworms following exposure to the carbamates.

Genomic and phenotypic analyses of Serratia fonticola strain GS2: a rhizobacterium isolated from sesame rhizosphere that promotes plant growth and produces N-acyl homoserine lactone

The genus Serratia incorporates many agriculturally important species. Serratia fonticola strain GS2, isolated from a sesame rhizosphere, can produce N-acyl homoserine lactone quorum sensing signal molecules and indole-3-acetic acid (IAA). Here we report the complete genome sequence and phenotypic characteristics based on genomic information of this bacterium. The complete genome sequence of S. fonticola strain GS2 consists of a chromosome of 6.1 Mbp and two plasmids of 132 kbp and 94 kbp. The genome clusters for IAA and N-acyl homoserine lactone biosynthesis were identified in the genome. Subsequently, the Salkowski test and gas chromatography-mass spectrometry (GC-MS) analysis also revealed that the strain GS2 produces indolic compounds (27.1μgmL-1) and IAA (6.7μgmL-1) in its culture broth. HPLC analysis confirmed that the strain GS2 produced the quorum sensing signal molecules N-hexanoyl-L-homoserine lactone and N-octanoyl-L-homoserine lactone. This new information on the genome sequence and phenotype features will inform future ecological studies related to plant-microbe interactions.

Acute Toxicity of Emulsifiable Concentrate of Coriander Essential Oils against Cyprinus carpio

Essential oils (EOs) extracted from plants possess various biological activities and have been considered as natural insecticides due to their potent insecticidal activities. In regard to develop natural insecticides, EOs are formulated as an emulsifiable concentrate and their acute toxicity against to fishes were determined in a static condition using Cyprinus carpio. Coriander EO was used as an active ingredient mixed with ethanol for solvent and various surface active agents. The tested EOs were obtained from a commercial market, and three different extractions were also undertaken to produce EO using steam distillation, solvent extraction, and supercritical fluid extraction. Among the emulsifiable concentrate including a commercial coriander EO, surface active agents such as Tween 80, sodium dodecyl benzene sulfonate (SDBS), and mixture of SDBS and Nonidet showed acute toxicity to the fish. With the three different EO extraction, coriander EO obtained from supercritical fluids with Triton X-100 exhibited acute toxicity to C. carpio. Taken together, Tetgitol and Nondet are considered as surface active agents for the emulsifiable formulation of coriander EO.

Synthesis and Pesticidal Activities of 5-(2-Cyclopropylaminopyrimidin-4-yl)-4-(thiophenyl)thiazole Derivatives

Pesticidal activities of 4-[5-(2-cyclopropylaminopyrimidin-4-yl)-4-(4-chloro-2-fluoro-phenyl)thiazol-2-yl]-1-methylpiperidine, designated as Comp I, have been determined against a mosquito larva, Culex pipiens pallens, and a phytopathogenic fungus, Phytophthora capsici. Comp I was used as the leading compound in this study. The compounds were synthesized by reacting them with two functional groups, 3-thiophenyl and 2-thiophenyl groups, instead of 4-chloro-2-fluorophenyl group in Comp I. Other functional groups such as 2-aminothiazole, 2-(1-methylpiperazin-4-yl)thiazole, and 2-(piperazin-4-yl)thiazole were also introduced instead of 2-methylpiperidin-4-yl-thiazole of Comp I. Compounds designated as XIII-6~XV-7 were newly synthesized and their structures were confirmed by 1H- and 13C-NMR spectroscopy. Mosquito larvicidal activities of all the synthesized compounds against C. pipiens pallens were examined and Comp I among them showed the strongest larvicidal activity as 0.513 mM of LC50 value. The fungicidal activities of all the synthesized compounds against P. capsici were examined using the whole plant method. Among the XIII-6~XV-7 chemicals, 5-(2-cyclopropylaminopyrimidin-4-yl)-4-(thiophen-2-yl)thiazol-2-amine (VIII-6) showed the most potent antifungal activity in vivo. While the EC50 value of the commercial fungicide dimethomorph was 4.26 μM, EC50 of VIII-6 was 0.94 μM. Therefore, thiazole derivatives can be considered as viable candidates for the control of mosquito larvae and plant diseases.