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        검색결과 952

        341.
        2016.04 구독 인증기관·개인회원 무료
        Beauveria bassiana (Bb) is an entomopathogenic fungus with a wide host range, and is commonly used as an environment-friendly biopesticide. However, the molecular mechanisms of Bb-host interactions are not well understood. Here, RNA isolated from a highly virulent strain of B. bassiana (Bb JEF-007) and Riptortus pedestris (Hemiptera: Alydidae) (bean bug) infected with this strain were subjected to high throughput next generation sequencing (NGS) to analyze and compare transcriptomes. Differentially expressed gene (DEG) analysis showed that 2,381 genes were up-regulated and 2,303 genes were down-regulated upon infection. Most DEGs were classified into the categories of single-organism, cellular and metabolism processes by gene ontology (GO) analysis. Carbon metabolism-related enzymes in the glyoxylate cycle were significantly up-regulated, suggesting a possible role for them in Bb growth in the host. This work provides insight into how entomopathogenic B. bassiana occupies agriculturally harmful bean bug at the late stage, which might be essential during fungal infection.
        342.
        2016.04 구독 인증기관·개인회원 무료
        Brachymystax lenok tsinlingensis (family Salmonidae), cold freshwater fish, is endemic to Asia. This species is currently distributed throughout Russia, Mongolia, China and the Korean Peninsula. B. lenok tsinlingensis in South Korea was severely affected by anthropogenic activities such as habitat destruction, agricultural run-off and water pollution, and hence this fish has recently been dramatically decreased in its population sizes and become now critically endangered. To recover the number of individuals of B. lenok tsinlingensis, stocking or translocation programs have been conducted continuously by local governments since 1970s. However, these programs made little effort to clarify populations that may have originated from stocked, translocated or introduced fish. An understanding of genetic characteristics of endangered populations is critical to develop effective conservation and restoration plans especially because genetic diversity ensues their future fate. Therefore, we assessed the “conservation status” of this species by estimating the level of genetic diversity and genetic structure among ten geographic populations including restored populations via reinforcement and supplementation. Also, we aimed to trace the genetic origins of the newly translocated population (Chiak) through a restoration practice program. Moreover, we inferred the phylogenetic relationships among Korean lenok populations as well as across the Northeast Asia. Two hundred eighteen individuals of B. lenok tsinlingensis were sampled from ten localities (Yanggu, Injae, Seorak, Bangtae and Hongcheon: North Han River basin; Pyeongchang, Chiak and Jeongseon: South Han River basin; Taebaek and Bonghwa: Nakdong River basin in South Korea). Based on mitochondrial DNA (mtDNA) control region and eight nuclear microsatellite loci, we found extremely low levels of within-population genetic diversity, which suggests small effective population sizes (Ne) within populations. For mtDNA control region, each population housed one, or at most, two haplotypes that are restricted to the respective localities, meaning that these ‘genetically unique’ lineages will be lost permanently if the local populations undergo extinction. The overall values of haplotype diversity (h) and nucleotide diversity (π) for the entire Korean population were 0.703 ± 0.024 and 0.021 ± 0.010, respectively. In the case of microsatellites, average number of alleles across the eight loci for the entire population was 9.1 and allelic richness (AR) per population ranged from 2.375 to 4.144 (mean = 3.104). The values of observed heterozygosity (HO) and expected heterozygosity (HE) were similar to each other [HO: 0.400 ~ 0.590 (mean = 0.518); HE: 0.407 ~ 0.608 (mean = 0.504)]. The inbreeding coefficient (FIS) values were generally low, ranging from 0.048 to 0.279. Consequently, the majority of the populations (except Yanggu and Pyeongchang) were not significantly deviated from Hardy-Weinberg equilibrium (HWE), suggesting random mating at these loci tested. In addition, we found that Korean lenok populations were significantly genetically isolated from each other, with private mtDNA haplotypes and microsatellite alleles, indicating limited gene flow among populations, strong effects of genetic drift due to small Ne, or a combination of both. The Mantel test of microsatellites revealed a significant correlation (r = 0.414, P = 0.04) between genetic and geographic distances for pairwise comparisons among the ten populations, while that of mtDNA showed a lack of correlation. Given the shared identical mtDNA haplotype and similar microsatellite allelic distributions between Chiak and Hongcheon populations, we suggest that the restored (introduced) Chiak population would be inferred to be genetically originated from Hongcheon population. Phylogenetic relationships among Northeast Asian populations showed that South Korean lineages have more recently diverged from China (Yellow River), than between North Korea and Russia. Although the phylogenetic relationship would be expected to be associated with geography, South-North Korea and China populations with a similar latitude was more phylogenetically closely related. These findings may suggest a possible scenario for the historical movements of B. lenok tsinlingensis in Northeast Asia during Last Glacial Maximum (LGM). It would be supported by the line of evidence that most lenok populations migrated to southward from Northern Asia such as Russia and Mongolia during LGM because the Korean Peninsula was landlocked as inland epoch and functioned as a southern shelter with Yellow River. For this reason, the Korean Peninsula is suggested to be an important geographical region for better understanding phylogenetic relationships and evolutionary histories of B. lenok tsinlingensis across the Northeast Asia. Despite large efforts made to develop several restoration programs in South Korea for B. lenok tsinlingensis, it is still unknown whether these past restoration efforts were successful or fruitless, mainly because of little attention paid to post-restoration monitoring research. Hence, there was a lack of their published official records. In the future, conservation and restoration projects of the Korean lenok populations should consider the genetic data for a better understanding of their ecological and evolutionary trajectories. And finally, we hope that our findings here can help inform on the future effective conservation and restoration plans for B. lenok tsinlingensis populatio ns in South Korea.
        343.
        2016.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        This study was conducted to determine the effects of supplementary lighting intensity and duration on selected Cassulaceae species grown in a hydroponic system. Five subfamilies in Crassulaceae with corresponding species were chosen as experimental units namely Sedeveria ‘Letizia ’, Sedum ‘Sun Red’, Crassula rupestris, Echeveria ‘Momotaro’, and Graptoveria opalina. Light duration (3 and 6 hours) and intensity (4,000 lux or 60 μmol • m−2 • s−1 and 8,000 lux or 120 μmol • m−2 • s−1), and their combinations served as factors which were replicated twice. Results revealed that the use of supplementary lighting using LED fixtures had influenced selected species under Crassulaceae. The use of three hours supplementary lighting under low light intensity had statistically similar results with those of the control S. letizia, C. rupestris and G. opalina in particular parameters. Meanwhile, succulents under six-hour with high intensity condition grew well, compared to species S. letizia, C. rupestris and E. ‘Momotaro,’ demonstrating that the data was significantly different. Interestingly, there were no statistical significant differences between species C. rupestris and the control regardless of change of variables (duration and intensity) in all parameters.
        4,000원
        344.
        2016.02 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        Multiple color selection techniques are successful in identifying quasars from wide-field broad- band imaging survey data. Among the quasars that have been discovered so far, however, there is a redshift gap at 5 . z . 5.7 due to the limitations of filter sets in previous studies. In this work, we present a new selection technique of high redshift quasars using a sequence of medium-band filters: nine filters with central wavelengths from 625 to 1025 nm and bandwidths of 50 nm. Photometry with these medium-bands traces the spectral energy distribution (SED) of a source, similar to spectroscopy with resolution R  15. By conducting medium-band observations of high redshift quasars at 4.7  z  6.0 and brown dwarfs (the main contaminants in high redshift quasar selection) using the SED camera for QUasars in EArly uNiverse (SQUEAN) on the 2.1-m telescope at the McDonald Observatory, we show that these medium-band filters are superior to multi-color broad-band color section in separating high redshift quasars from brown dwarfs. In addition, we show that redshifts of high redshift quasars can be determined to an accuracy of z/(1 + z) = 0.002 – 0.026. The selection technique can be extended to z  7, suggesting that the medium-band observation can be powerful in identifying quasars even at the re-ionization epoch.
        4,200원
        345.
        2015.12 구독 인증기관 무료, 개인회원 유료
        Obesity is a risk factor for various diseases, including cardiovascular disease, diabetes, renal disease, hypertension, cancer, and neural disease. Adipose tissue in animals is important for the mobilization of lipids, milk production, deposition of fat in different depots, and muscle and meat production. Understanding the genetic and physiological causes of metabolic disease is a priority in biomedical genome research. In this study, we examined several variables in mice fed a high-fat diet, including serum composition, body weight, total calorie intake, and differentially expressed genes. Body weight and blood glucose levels were not significantly different between animals fed high-fat and normal diets. However, high-fat diet groups showed reduced calorie and food intakes. Levels of sodium, ionized calcium, glucose, hematocrit, hemoglobin, pH, PCO2, PO2, TCO2+, HCO3+, base excess, and SO2 in the blood were not significantly different between mice fed high-fat and normal diets. Serum potassium concentration, however, was lower in mice a high-fat diet. Differentially expressed genes were also compared between the two groups. The purpose of this study was to discover new genes as a result of annealing control primer (ACP) PCR using 20 random primers. Five down regulated genes were identified and three of others were up-regulated by high-fat diet. Known genes were excluded from this result. In addition, the relationships among candidate genes and high-fat diet should be investigated according to potassium concentration in the blood. In conclusion, mice fed normal and high-fat diets showed no significant difference in body weight, whereas high-fat diet led to changesin blood composition and differential expression of several genes. These findings may provide a better understanding of the mechanisms underlying the association between obesity and metabolic diseases.
        4,000원
        346.
        2015.11 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        In this work, on-site corrosion behavior of heat resistant tubes of T91, used as components of a superheater in a power plant for up to 25,762 h, has been investigated using scanning electron microscopy(SEM), energy dispersive X-ray spectroscopy (EDS), and electron backscattered diffraction(EBSD), with the objectives of studying the composition, phase distribution, and evolution during service. A multi-layer structure of oxide scale was found on both the steamside and the fireside of the tube surface; the phase distribution was in the order of hematite/magnetite/spinel from the outer to the inner matrix on the steamside, and in the order of slag/magnetite/spinel from the outer to the inner matrix on the fireside. The magnetite layer was found to be rich in pores and cracks. The absence of a hematite layer on the fireside was considered to be due to the low oxygen partial pressure in the corrosion environment. The thicknesses of the hematite and of the slag-deposit layer were found to exhibit no significant change with the increase of the service time.
        3,000원
        347.
        2015.11 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        The microstructural evolution of Grade 91 tempered martensite ferritic steels heat treated at 760~1000 oC for two hours was investigated using scanning electron microscopy(SEM), energy disperse spectroscopy(EDS), electron backscattered diffraction (EBSD), and transmission electron microscopy(TEM); a microhardness tester was also employed, with a focus on the grain and precipitate evolution process as well as on the main hardening element. It was found that an evolution of tempered martensite to ferrite(760~850 oC), and to fresh martensite(900~1000 oC), occurred with the increase of temperature. Simultaneously, the parabolic evolution characteristics of the low angle grain boundary(LAGB) increased with the increase of the heating temperature(highest fraction of LAGB at 925 oC), indicating grain recovery upon intercritical heating. The main precipitate, M23C6, was found to be coarsened slightly at 760~850 oC; it then dissolved at 850~1000 oC. Besides this, M3C cementite was formed at 900~1000 oC. Finally, the experimental results show that the hardness of the steel depended largely on the matrix structure, rather than on the precipitates, with the fresh martensite showing the highest hardness value.
        4,000원
        348.
        2015.11 KCI 등재 구독 인증기관 무료, 개인회원 유료
        농진청에서 수행하고 있는 아프리카 국제협력프로그램인KAFACI 사업의 일환으로 우간다 등 8개국에 ‘통일형 다수성벼 품종개발’ 사업을 추진하고 있다. 이를 위해 아프리카에서정상적인 생육과 수량을 나타내는 다수성 통일형 품종인 밀양23호와 아프리카의 재래종인 O. glaberrima를 이용하여 밀양23호의 유전적배경을 보유한 근동질 계통인 BC4F1을 육성하고, 약배양을 통해 유전적 고정계통을 육성하였다. 이 중 50개계통을 우간다에서 생물검정을 실시한 결과, 아프리카에서 문제시되는 Yellow Mottle Virus (RYMV), Bacterial LeafStreak(BLS), 흰잎마름병 및 도열병에 복합저항성인 계통으로판명되었다. 특히 RYMV에 대한 저항성은 저항성원이 결여되어 있는 병으로 본 연구를 통해 육성한 계통들은 향후 아프리카에 적응하는 내병성 다수성 품종개발에 유용한 재료를 활용 될 것으로 생각된다.
        4,000원
        357.
        2015.10 구독 인증기관·개인회원 무료
        Insect growth regulators (IGRs) are compounds that induce developmental anomalies such as premature molting or supernumerary larval stages. IGRs can be divided into 3 groups based on their mode of action, one of which is known as the juvenile hormone agonists (JHAs). Previously, we have developed a novel screening method which can identify juvenile hormone antagonists (JHANs) using a yeast-two hybrid system incorporating Aedes aegypti juvenile hormone receptor complex proteins (MET and FISC). It has been reported that plants may use IGRs in their defenses against insect herbivores. In this study, 171 plant essential oil samples were screened using the yeast-two hybrid system in order to identify JHAs and/or JHANs. Eight out of 171 samples, 4 JHA and 4 JHAN candidates, were selected and their insecticidal activities were investigated against A. aegypti larvae. They showed high levels of insecticidal activities, with LC50 values ranging from 11.2~21.4 ug/ml. These results indicate that plants do use JHAs and/or JHANs as a part of their defenses against insect herbivores. Also, JHAs and JHANs identified in this study could be exploited as effective biological control agents.
        358.
        2015.10 구독 인증기관·개인회원 무료
        Insect growth regulators (IGRs) are insecticides that disrupt the normal development of target insects by inducing symptoms such as premature molting or supernumerary larval stages. IGRs are categorized into three types based on their mode of action. One of the them is classified as juvenile hormone agonists (JHAs). Recently, we developed a yeast-two hybrid system that can identify potential juvenile hormone antagonist (JHAN) candidates using Aedes aegypti juvenile hormone receptor complex proteins, known as MET and FISC. In order to identify novel JHAN compounds, approximately 8,700 basic chemical compounds were screened using the yeast-two hybrid system. Among them, 35 compounds were first selected based on consistency of JHAN activity, and their insecticidal activities were investigated against A. aegypti larvae. These compounds showed insecticidal activities about 1.7~3 times higher than that of pyriproxifen, which is a well known JHA insecticide. These results suggested that these JHANs can be used as effective JHAN insecticides.
        359.
        2015.10 구독 인증기관·개인회원 무료
        Insect Growth Regulators (IGRs) are insecticides that disrupt the normal development of target insects by inducing symptoms such as premature molting or supernumerary larval stages. Juvenile hormone systems become the targets of two types of IGRs: the Juvenile Hormone Agonists (JHAs) and Juvenile Hormone Antagonists (JHANs). Pyriproxyfen is one of the chemical compounds widely used as JHA to control many kinds of insects while Kanakugiol is a plant-extracted compound which acts as JHAN. The small brown planthopper, Laodelphax striatellus, is one of the most serious pest insects of rice plants because it can transmit the rice stripe virus which often causes significant reduction of yield in the field. In order to analyze the differential gene expressions of L. striatellus upon JHA and JHAN treatment by using next generation sequencing technique, we sprayed Pyriproxyfen and Kanakugiol on 4th instar nymphs of L. striatellus respectively, and extracted total RNA for RNA-seq. The quality-filtered Illumina sequence reads of the control, JHA, and JHAN treated samples were mapped to the reference gene sequences by using the Bowtie2 software. Then the results of mapping by Bowtie2 were analyzed by eXpress software to quantity the differential gene expression.
        360.
        2015.10 구독 인증기관·개인회원 무료
        Recently, Bacillus thuringiensis (Bt) cry genes encoding insecticidal Cry proteins have been widely applied for the construction of transgenic crops resistant to insect pests. This study aimed to construct novel mutant cry1Ac genes for genetically modified crops with enhanced insecticidal activities. Using multi-site directed mutagenesis, 34 mutant cry1Ac genes were synthesized and converted at 24 amino acid residues, located on domain I (8 residues) and domain II (16 residues). These mutant genes were expressed as a fusion protein with polyhedrin using the baculovirus expression system. The expressed proteins were occluded into polyhedra and activated stably to 65 kDa by trypsin. Among these, Mut-N04, N06, and N16 showed high levels of insecticidal activites against larvae of Plutella xylostella, Spodoptera exigua, and Ostrinia furnacalis. Mut-N16, which showed the highest insecticidal activity, is expected to be a desirable cry gene for introduction into transgenic crops. This study could provide useful means to construct mutant cry genes with improved insecticidal activities and expanded host spectrum for transgenic crops.