• Title, Summary, Keyword: 아이코사노이드

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Change in Hemocyte Populations of the Beet Armyworm, Spodoptera exigua, in Response to Bacterial Infection and Eicosanoid Mediation (세균 감염에 따른 파밤나방 혈구 밀도 변화와 아이코사노이드 중개 역할)

  • Park, Jiyeong;Kim, Yonggyun
    • Korean journal of applied entomology
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    • v.51 no.4
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    • pp.349-356
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    • 2012
  • Eicosanoid mediates various cellular immune responses in insects. This study aimed to discover its novel action on the modulation of hemocyte populations in response to an immune challenge. Upon bacterial challenge, the last instar larvae of the beet armyworm, Spodoptera exigua, increased their total hemocyte density in 2 h, and then decreased it to a basal hemocyte density level. This rapid increase in total hemocyte density was explained by an increase of plasmatocyte and spherulocyte densities. When larvae were treated with dexamethasone (a specific phospholipase $A_2$ ($PLA_2$) inhibitor), they did not show any increase in hemocyte density in response to bacterial challenge. However, the addition of arachidonic acid (a catalytic product of $PLA_2$) to larvae treated with dexamethasone recovered the up-regulation of hemocyte density in response to bacterial infection. Among eicosanoid, cyclooxygenase (COX), but not lipoxygenase (LOX), products seemed to mediate the increase of hemocyte density in response to bacterial infection because naproxene (a COX inhibitor) inhibited the hemocyte density increase, though esculetin (a LOX inhibitor) did not. Prostaglandin $E_2$, a COX product, significantly increased the hemocyte density even without bacterial infection. These results suggest that eicosaniod mediates a rapid increase in total hemocyte density in response to immune challenge.

Inhibitory Effects of an Eicosanoid Biosynthesis Inhibitor, Benzylideneacetone, Against Two Spotted Spider Mite, Tetranychus urticae, and a Bacterial Wilt-causing Pathogen, Ralstonia solanacearum (아이코사노이드 생합성 저해제인 벤질리덴아세톤의 점박이응애(Tetranychus urticae)와 세균성풋마름병 세균(Ralstonia solanacearum)에 대한 억제효과)

  • Park, Ye-Sol;Kim, Min-Je;Lee, Geon-Hyung;Chun, Won-Soo;Yi, Young-Keun;Kim, Yong-Gyun
    • The Korean Journal of Pesticide Science
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    • v.13 no.3
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    • pp.185-189
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    • 2009
  • A monoterpenoid compound, benzylideneacetone (BZA), is a metabolite of an entomopathogenic bacterium, Xenorhabdus nematophila. Its primary biological activity is an inhibitor of phospholipase $A_2$, which catalyzes the committed step of biosynthesis of various eicosanoids that are critically important to mediate insect immune responses. When BZA was applied to two-spotted spider mite, Tetranychus urticae, it exhibited a dose-dependent mortality in leaf-disc assay. Subsequently BZA was tested against T. urticae infesting apples in a field orchard, in which it showed a significant control efficacy, which was not statistically different with that of a commercial acaricide. BZA also had significant antibacterial activities against three species of plant pathogenic bacteria when it was added to the bacterial cultures, in which it showed the highest inhibitory activity against a bacterial wilt-causing pathogen, Ralstonia solanacearum. The bacterial pathogen caused significant disease symptom to young potato plants. However, BZA significantly suppressed the disease occurrence. This study suggests that BZA can be used to develop a novel crop protectant to control mite and bacterial pathogen.

Fatty Acid Composition of Different tissues of Spodoptera exigua Larvae and a Role of Cellular Phospholipase A2 (파밤나방 유충의 조직별 지방산 구성과 세포성 인지질분해효소의 역할)

  • Kim, Yonggyun;Lee, Seunghee;Seo, Seunghwan;Kim, Kunwoo
    • Korean journal of applied entomology
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    • v.55 no.2
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    • pp.129-138
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    • 2016
  • Eicosanoids are a group of C20 oxygenated polyunsaturated fatty acids (PUFAs). To monitor biosynthetic precursors of these PUFAs, this study extracted fatty acids from different tissues of the beet armyworm, Spodoptera exigua, and assessed their compositions using GC/MS. Fifth instar larvae were dissected to isolate different tissues of gut, fat body, hemocytes, and integument. From each tissue, total lipids were extracted and fractionated into neutral lipid (NL), glycolipid (GL), and phospholipid (PL). Most tissues contained palmitic acid (16:0), stearic acid (18:0), oleic acid (18:1), linoleic acid (18:2), and linolenic acid (18:3). However, their compositions were different among tissues and lipid types. Fat body and hemocytes possessed other type of fatty acids such as myristic acid (14:0) and three unknown fatty acids. Among lipid types, PL contained relatively high levels of linolenic acid than NL and GL, while it had lower saturated fatty acids. Total unsaturated fatty acid composition was varied among tissues and lipid types. PL was rich in unsaturated fatty acids in fat body, gut, and hemocytes. There was a significant influence of calcium-independent phospholipase $A_2$ ($iPLA_2$) on maintaining fatty acid composition because RNA interference of $iPLA_2$ expression significantly modified fatty acid compositions in NL and PL. However, this study did not detect arachidonic acid, a main eicosanoid biosynthesis precursor, in all tissues. This suggests an alternative biosynthesis of eicosanoids in insects, which is distinct from the biosynthetic pathway of mammals.

Effect of Cellular Phospholipase A2 Inhibition on Enhancement of Bt Insecticidal Activity (세포성 인지질분해효소 활성 억제에 따른 비티 살충력 증가 효과)

  • Eom, Seonghyeon;Park, Jiyeong;Kim, Kunwoo;Kim, Yonggyun
    • Korean journal of applied entomology
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    • v.53 no.3
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    • pp.271-280
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    • 2014
  • Some bacterial metabolites of Xenorhabdus nematophila (Xn) inhibit phospholipase $A_2$ ($PLA_2$) activity to shutdown eicosanoid biosynthesis in target insects. However, little has been known about the target insect $PLA_2$ of these bacterial metabolites. Eight bacterial metabolites identified in Xn culture broth exhibited significant insecticidal activities against larvae of both lepidopteran species of Plutella xylostella and Spodoptera exigua. Moreover, these bacterial metabolites significantly enhanced insecticidal activities of Bacillus thuringiensis (Bt). To determine target $PLA_2$, we cloned and over-expressed cellular $PLA_2$ ($SecPLA_2$) of S. exigua. Purified $SecPLA_2$ catalyzed phospholipids derived from the fat body and released several polyunsaturated fatty acids. Most Xn metabolites significantly inhibited $SecPLA_2$ activity, but were different in their inhibitory activities. There was a positive correlation between the inhibition of $SecPLA_2$ and the enhancement of Bt insecticidal activity. These results indicate that $SecPLA_2$ is a molecular target inhibited by Xn metabolite.

A Technique to Enhance Insecticidal Efficacy Using Bt Cry Toxin Mixture and Eicosanoid Biosynthesis Inhibitor (혼합 비티 독소단백질과 아이코사노이드 생합성 억제자를 이용한 약효 증진 기술)

  • Eom, Seonghyeon;Park, Youngjin;Kim, Yonggyun
    • The Korean Journal of Pesticide Science
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    • v.19 no.3
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    • pp.301-311
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    • 2015
  • To enhance Bacillus thuringiensis (Bt) efficacy, four Cry toxins were purified from four different Bt strains and assessed in their combined efficacy. The Cry mixtures significantly expanded their target insect spectra. Bacterial culture broth of Xenorhabdus nematophila (Xn) significantly suppressed insect cellular immune response and increased Cry toxicity. The addition of Xn culture broth to Cry mixture significantly enhanced Bt efficacy in target insect spectrum and insecticidal activity.

Immunosuppressive Activity of an Entomopathogenic Bacteria, Xenorhabdus ehlersii KSY, and Its Application to Enhance Insecticidal Activity of Bacillus thuringiensis (곤충병원세균(Xenorhabdus ehlersii KSY)의 곤충면역 억제 능력과 이를 이용한 Bacillus thuringiensis 의 살충력 증가 효과)

  • Kim, Hyoil;Kim, Yonggyun
    • Korean journal of applied entomology
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    • v.58 no.2
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    • pp.101-109
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    • 2019
  • An entomopathogenic bacterium, Xenorhabdus ehlersii KSY, is symbiotic to a nematode, Steinernema longicaudum, and exhibits high entomopathogenic virulence against lepidopteran insects. This study showed that the bacterial pathogenicity is induced by its inhibitory activity against eicosanoid biosynthesis of target insects, resulting in immunosuppression. To be applied for insect pest control, the bacteria should be infected to insect hemocoel. To deliver X. ehlersii to inset hemocoel, Bacillus thuringiensis (Bt) was mixed with the bacteria to breakdown the physical barrier (= midgut epithelium) from midgut lumen to hemocoel. The bacterial mixture significantly enhanced insecticidal activity of Bt only against larvae of Plutella xylostella and Maruca vitrata. For formulation, X. ehlersii cells were freeze-dried and mixed with sporulated Bt cells. The formulated bacterial mixture was applied to semi-field cultivating cabbage crop infested by P. xylostella. The bacterial mixture treatment showed over 95% control efficacy, while Bt alone gave 80% control efficacy. These results suggest that X. ehlersii can be applied to develop a novel insect control agent.

Study on Development of Novel Biopesticides Using Entomopathogenic Bacterial Culture Broth of Xenorhabdus and Photorhabdus (Xenorhabdus 및 Photorhabdus 세균 배양액을 이용한 생물농약 개발에 관한 연구)

  • Seo, Sam-Yeol;Kim, Yong-Gyun
    • Korean journal of applied entomology
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    • v.49 no.3
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    • pp.241-249
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    • 2010
  • Two groups of entomopathogenic bacteria, Xenorhabdus and Photorhabdus, are known to suppress insect immune responses by inhibiting eicosanoid biosynthesis. This study used these bacterial culture broths to develop novel biochemical insecticides against the diamondback moth, Plutella xylostella. Though the bacterial culture broths alone showed little insecticidal activity, they significantly enhanced pathogenicity of Bacillus thuringiensis against the fourth instar larvae of P. xylostella. Sterilization of the bacterial culture broth by autoclaving or $0.2\;{\mu}m$ membrane filtering did not influence the synergistic effect on the pathogenicity of B. thuringiensis. Three metablites identified in the culture broth of X. nematophila also showed similar synergistic effects. In field test, both entomopathogenic bacterial culture broth also enhanced the control efficacy of B. thuringiensis against P. xylostella.

Structure-activity Analysis of Benzylideneacetone for Effective Control of Plant Pests (벤질리덴아세톤 화학구조 변이에 따른 생리활성 변화 분석 및 식물 병해충 방제 효과)

  • Seo, Sam-Yeol;Jun, Mi-Hyun;Chun, Won-Su;Lee, Sung-Hong;Seo, Ji-Ae;Yi, Young-Keun;Hong, Yong-Pyo;Kim, Yong-Gyun
    • Korean journal of applied entomology
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    • v.50 no.2
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    • pp.107-113
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    • 2011
  • Benzylideneacetone (BZA) is a compound derived from culture broth of an entomopathogenic bacterium, Xenorhabdus nematophila (Xn). Its immunosuppressive activity is caused by its inhibitory activity against eicosanoid biosynthesis. This BZA is being developed as an additive to enhance control efficacy of other commercial microbial insecticides. This study was focused on the enhancement of the immunosuppressive activity of BZA by generating its chemical derivatives toward decrease of its hydrophobicity. Two hydroxylated BZA and one sugar-conjugated BZA were chemically synthesized. All derivatives had the inhibitory activities of BZA against phospholipase $A_2$ ($PLA_2$) and phenoloxidase (PO) of the diamondback moth, Plutella xylostella, but BZA was the most potent. Mixtures of any BZA derivative with Bacillus thuringiensis (Bt) significantly increased pathogenicity of Bt. BZA also inhibited colony growth of four plant pathogenic fungi. However, BZA derivatives (especially the sugar-conjugated BZA) lost the antifungal activity. These results indicated that BZA and its derivatives inhibited catalytic activities of two immune-associated enzymes ($PLA_2$ and PO) of P. xylostella and enhanced Bt pathogenicity. We suggest its use to control plant pathogenic fungi.