• Korean journal of applied entomology
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• v.61 no.1
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• pp.85-90
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• 2022

Insulin and insulin-like growth factor-1 (IGF-1) are hormones that play an important role in the physiological regulation of metabolism, growth, and longevity in vertebrates. Likewise, insulin-like peptides (ILPs), which are structurally similar to insulin and IGF-1, are crucial in insect physiology. In this review, we present an integrated summary of insect ILPs and their receptor signaling, which has been shown to be comparable to insulin and IGF-1 receptor signaling in vertebrates based on genetic studies of Drosophila melanogaster. Additionally, we review the control of ILP synthesis and secretion in the brain in response to nutrition, as well as the ILPs' physiological role in insect metabolism. Moreover, we discuss the contribution of ILPs to growth, development, reproduction, and diapause. Finally, we consider the possibility of targeting ILP receptor signaling in pest management.

• Korean journal of applied entomology
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• v.49 no.4
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• pp.409-416
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• 2010

An entomopathogenic bacterium, Photorhabdus temperata ssp. temperata (Ptt), suppresses insect immune responses and facilitates its symbiotic nematode development in target insects. The immunosuppressive activity of Ptt enhances pathogenicity of various microbial pesticides including Bacillus thuringiensis (Bt). This study was performed to select a cheap and efficient bacterial culture medium for large scale culturing of the bacteria. Relatively cheap industrial bacterial culture media (MY and M2) were compared to two research media, Luria-Bertani (LB) and tryptic soy broth (TSB). In all tested media, a constant initial population of Ptt multiplied and reached a stationary phase at 48 h. However, more bacterial colony densities were detected in LB and TSB at the stationary phase compared to two industrial media. All bacterial culture broth gave significant synergism to Bt pathogenicity against third instars of the diamondback moth, Plutella xylostella. Production of bacterial metabolites extracted by either hexane or ethyl acetate did not show any significant difference in total mass among four culture media. Reverse phase HPLC separated the four bacterial metabolites, which were not much different in quantities among four bacterial culture broths. This study suggests that two industrial bacterial culture media can be used to economically culture Ptt in a large scale.

• Korean journal of applied entomology
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• v.50 no.3
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• pp.171-178
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• 2011

Bacillus thuringiensis (Bt) is a bacterial biopesticide against insect pests, mainly lepidopterans. Spodoptera exigua and Plutella xylostella exhibit significant decreases in Bt susceptibility in late larval instars. To enhance Bt pathogenicity, we used a mixture treatment of Bt and other bacterial metabolites which possessed significant immunosuppressive activities. Mixtures of Bt with culture broths of Xenorhabdus nematophila (Xn) or Photorhabdus temperata ssp. temperata (Ptt) significantly enhanced the Bt pathogenicity against late larval instars. Different ratios of Bt to bacterial culture broth had significant pathogenicities against last instar P. xylostella and S. exigua. Five compounds identified from the bacterial culture broth also enhanced Bt pathogenicity. After determining the optimal ratios, the mixture was applied to cabbage infested by late instar P. xylostella or S. exigua in greenhouse conditions. A mixture of Bt and Xn culture broth killed 100% of both insect pests when it was sprayed twice, while Bt alone killed less than 80% or 60% of P. xylostella and S. exigua, respectively. Other Bt mixtures, including Ptt culture broth or bacterial metabolites, also significantly increased pathogenicity in the semi-field assays. These results demonstrated that the Bt mixtures collectively names "Bt-Plus" can be developed into potent biopesticides to increase the efficacy of Bt.

• Proceedings of the Korean Society of Applied Entomolohy Conference
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• 2002.11a
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• pp.165-165
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• 2002

• 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.

• Korean journal of applied entomology
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• v.61 no.1
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• pp.143-154
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• 2022

Plant secondary metabolites play an important role in insect-plant interactions. Herbivorous insects have various strategies to cope with the plant defensive compounds. Polyphagous insects feed on a wide variety of plant species, and their detoxification mechanisms are more complex since they tend to respond to a large array of different plant-derived chemicals. Alternatively, oligophagous insects specialize on only a few related plant species and may be expected to have a more efficient form of adaptation. This adaptation could involve either the production of large quantities of enzymes to detoxify their defensive compounds or the sequestration of the compounds or their metabolites. The oriental tobacco budworm, Helicoverpa assulta, is a specialist herbivore, feeding on a few plants of Solanaceae, such as tobacco and hot pepper. Understanding its host-plant adaptation not provides an important insight on physiology, ecology and evolution of specialist herbivores, but also gives a clue to develop management strategies of the pest species such as H. assulta. This paper briefly reviews the specialist, H. assulta, focusing on its host range, larval associations with the host plants, and detoxification mechanisms to nicotine and capsaicin, two characteristic defensive compounds derived from its two major host plants, tobacco and hot pepper, respectively. It summarizes the relevant research over the last half century and provides a future perspective on this subject.

• Journal of Sericultural and Entomological Science
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• v.38 no.2
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• pp.186-188
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• 1996

곤충애 있어서 호르몬의 작용기작과 그 이용에 관하여 요야하면 다음과 같다. 곤충호르몬에는중추신경계의 신경분비세포에서 합성, 분비되는 peptide의 neuropeptide hormone (PTTH, bombyxin, diapause hormone등)이 있고, 상피계의 내분비선에서 합성, 분비되는 sesquiterpene의 유약호르몬 ( juvenile hormone)과 steroid의 탈피호르몬 (ecdysone)이 있다. 곤충호르몬은 특정한 표족세포에 있는 수용체와 높은 특이성과 높은 친화성을 가지고 결합해서 세포의 작용을 조절한다. 일반적으로 peptide hormone은 표적세포의의 세포막을 통과할 수 없으므로 표적세포의 막표면에 있는 수용체와 결합하는 것에 의해 세포내 대사제를 활성화시킴으로서 peptide hormone의 특이적인 발현이되는 것으로 알려지고 있다. 한편, ecdysone과 같은 steriod hormone이나 juvenlie hormone은 표적세포의 세포막을 용이하게 통과할수 있으므로 세포내의 세포막을 용이하게 통과할 수 있으므로 세포내로 들어가 수용체와 결합해서 hormone-receptor comlpex는 핵내로 들어가 DNA의 특이적인 영역에 결합하므로서 이들 호르몬 특이적인 기능이 발현되는 것으로 알려져 있다. Ecodysone의 활성이 있는 ecdysteroid가 여러 식물에서 발견되고 있어, 금후 양잠의 상족에 이용이 기대되고 있다. 또한, 향유약호르몬(AJH) 활성물지인 imidazole계 화합물은 양잠에 있어서 세섬도고치 생산에 그 이용이 기대되고 있다.

• Korean Journal of Environmental Agriculture
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• v.38 no.4
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• pp.296-306
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• 2019

BACKGROUND: Temperature is known to be the main factor affecting development, growth and reproduction of organisms and also a physical factor directly related to insect survival. Insects as ectothermal species should be responsive to climate changes for their survival and develop various survival strategies under the unfavorable temperature such as low temperature. The purpose of this study is to identify genes contributing to adaptation of low temperature. METHODS AND RESULTS: To identify genes contributing to adaptation of low temperature, the transcriptomic data were obtained from fat body in Plutella xyostella larvae via next generation sequencing. We identified structural proteins, heat shock proteins, antioxidant enzymes, detoxification proteins, and cryoprotectant mobilization and biosynthesis-related proteins. Genes encoding chitinase, cuticular protein, Hsp23, chytochrome protein, Glutathione S transferase, and phospholipase 2 were up-regulated under low temperature. Proteins related to energy metabolism such as UDP-glycosy ltransferase, trehalase and trehalose transporter were down-regulated. CONCLUSION: When insect pests were exposed to low temperature, changes in gene expression of fat body could provide some hints for understanding temperature adaptation strategies.

• Korean journal of applied entomology
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• v.49 no.3
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• pp.251-259
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• 2010

A bacterial colony was isolated from the gut of the bean bug, Riptortus clavatus. From morphological and biochemical tests, the bacterial isolate showed the highest similarity to Staphylococcus succinus. DNA sequence of 16S rRNA gene of the bacterium supported the identification. Oral administration of penicillin G to adults of R. clavatus gave a dose-dependent mortality of adults of R. clavatus to adults along with significant decrease of the bacterial population in the gut. Similarly, three metabolites (benzylideneacetone, proline-tyrosine, and acetylated phenylalanine-glycine-valine) derived from an entomopathogenic bacterium, Xenorhabdus nematophila, also inhibited growth of the gut bacterial population and gave significant mortalities to R. clavatus. These results suggest that a gut bacterial population classified as Staphylococcus sp. is required for survival of R. clavatus and that the three bacterial metabolites had toxic effects on the bugs due to their antibacterial properties.

• Korean journal of applied entomology
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• v.30 no.1
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• pp.10-17
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• 1991

Cuticular penetration and detoxication as mechanisms of resistance to the carbamate insecticides in fenobucarb-selected($R_{f}$) and carbofuran-selected($R_{c}$) strains of the brown planthopper (N. lugens Stal) were investigated. Rates of penetration were not significantly different in the susceptible and resistant strains. However, total amount of excretion of the $R_{f}$ and $R_{c}$ strains were much larger than that of the susceptible strain. Fenovucarb and carbofuran were in vivo metabolizd much faster in the $R_{f}$ strain than in the susceptible strain. OSBP(o-sec-butyl phenol) and 3-ketocarbofuran phenol were invitro the major metabolites of fenobucarb and carbofuran in the brown planthopper, respectively. Total amount of the two major metabolites were produced abotu 2 times larger in the $R_{f}$ and $R_{c}$ strains compared to the susceptible strain. OSBP and 3-ketocarbofuran phenol were not so toxic to the brown planthopper ($LD_{50}$ >100 $\mu\textrm{g}$/g hopper). Based on our data, detoxication plays a large role in resistance to fenobucarb and carbofuran in the resistant strain of BPH, although several resistance factors maybe involved.