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 (JH)-based IGRs are of particular interest because they simulate or interfere with the formation of juvenile hormone receptor complex. Insect larvae generally have been poorly susceptible to JH agonists (JHAs) because endogenous JH titer is already high in the larval stage. In contrast, JH antagonists (JHANs) might be more effective for control of target pests in larval stages through interference in the status quo action of JHs. In this study, we tested 2,354 chemical compounds using the yeast-two hybrid system to identify JHANs. Among them, K265674 sample was selected and its insecticidal activity was evaluated against Aedes albopictus larvae. These results may be useful for development of novel IGR insecticide.

Recent studies suggested that gut symbionts modulate insect development and reproduction. However, how gut symbionts modulate host physiologies and what types of molecules are involved in these changes are still unclear. When we analyzed hemolymph proteins and transcriptional levels of host insects, hexamerin-α (Hex-α), hexamerin-β (Hex-β) and vitellogenin-1 (Vg-1) were highly expressed in symbiotic insects (Sym) compared to aposymbiotic insects (Apo). Depletion of Hex-β by RNA interference in 2nd Sym-nymphs delayed adult emergence, whereas Hex-α and Vg-1 RNA interference in 5th nymphs decreased reproduction of female insects and caused loss of color of laid eggs. Also, the levels of JHSBIII of Riptortus host were 3-fold higher in the Sym-female insects compared to the Apo-insects. These results demonstrate that the Burkholderia gut symbiont modulates host development and egg production through regulating the expression of three host storage proteins by controlling of brain hormone.

Insect growth regulators (IGRs) are attractive pest control agents due to their high target specificity and relative safety to the environment. Recently, plants have been shown to synthesize IGRs that affect the insect juvenile hormone (JH) as a part of their defense mechanisms. We identified several JH agonists (JHAs) and antagonists (JHANs) from plant essential oil compounds using a yeast two-hybrid system transformed with the Aedes aegypti JH receptor as a reporter system. They showed high mosquitocidal activities with relatively low LC50 values and caused retardation of ovarian development in female mosquitoes. While the JHAs increased the expression of JH-induced gene, the JHANs caused reduction in the expression of the same gene. The compounds identified in this study could provide insights on the plant-insect interactions and may be useful for the development of novel IGR insecticides.

Entomopathogenic fungi have been widely studied for their potential as the effective biological control agents. They produce variety of secondary metabolites with insecticidal activities, and it is reasonable to assume that entomopathogenic fungi might produce secondary metabolites modulating juvenile hormone for their survival against defense mechanisms of host insect. In this study, Beauveria spp. and Lecanicillium spp. strains cultured on unpolished rice medium were extracted with acetone. Both extracts showed juvenile hormone antagonist (JHAN) activities in the yeast-two hybrid β-galactosidase assay. In addition, they showed high insecticidal activities against Aedes albopictus, Plutella xylostella, and Ostrinia furnacalis. These results suggested that secondary metabolites of entomopathogenic fungi could be useful for development of novel IGR insecticides.

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). In recent studies, we identified juvenile hormone antagonists (JHANs) from plant extracts. In order to identify a novel juvenile hormone agonists and antagonists, we tested 2,354 chemical compounds using the yeast-two hybrid system. Among them, 2 JHAs and 4 JHANs were selected and their insecticidal activities were evaluated against Aedes albopictus larvae. These results may be useful for development of novel IGR insecticides.

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.

Insects impact human health through vector-borne diseases and cause major economic loses through damaging crops and stored agricultural products. Insect-specific growth regulators (IGR) represent attractive control agents because of their safety to the environment and humans. Here, we report identification of plant compounds that are antagonists of the insect-specific juvenile hormone (PJHANs), using the yeast two hybrid system transformed with the mosquito JH receptor as a reporter assay. We show that these compounds act by inhibiting larval growth and reproduction in mosquitoes. We also demonstrate that PJHANs affect the JH receptor, Methoprene-tolerant (Met), by disrupting its complex with CYCLE, formation of which is required for mediating JH action. We isolated five diterpene secondary metabolites with JH antagonist activity from two plants, Lindera erythrocarpa and Solidago serotina. They are effective in causing mortality of mosquito larvae at relatively low LD50 values. Two of these diterprenes affect Met function, leading to reduction in expression of Met target genes and causing retardation of follicle development in mosquito ovaries. Developing potent compounds counteracting JHaction (JH antagonists) would find a wider range of control applications. However, so far such JH antagonists have not been developed. Here, we report the discovery of potent JH antagonists in plants, which represents an innate resistance mechanism of plants against insect herbivores. These newly discovered plant JH antagonist compounds could be used as the starting material for developing novel insecticides.

The Riptortus-Burkholderia symbiosis is a newly emerging insect-bacterium symbiotic system. This symbiosis system has a good merit as an experimental model system to produce the non-symbiotic (apo) and symbiotic (sym) host insect. In recent reported papers, the symbionts play important biological roles for the host insects. Meanwhile, juvenile hormone (JH) is one of major hormone synthesized corpora allata(CA) to control many physiology of insect. However, the study for cross-talk mechanism between symbionts and host hormones to control important physiological phenomenon of insects is almost none. In this study, we found that Riptortus speed up adult emerging and increase egg laying on presence of symbiont Burkholderia. Also we found that hexamerin proteins, which were controlled the expression by JH, were accumulated in sym-Riptortus hemolymph compare with apo-Riptortus. According as combined results, we hypothesized that the gut symbiont Burkholderia can control JH titer to conclude out beneficial effects such as development and reproduction of R. pedestris. To verify this hypothesis, we examined measurement of JH titer, expression of hexamerins as JH response genes and RNAi for hexamerin protein during whole Riptortus life on presence or absence of symbiont Burkholderia. All results demonstrated that gut symbiont controlled JH titer of Riptortus. Controlled JH amount by symbiont Burkholderia in host midgut regulated hexamerin protein expression for speeding up adult emerging and increasing egg production.

Juvenile hormone is the most important hormone inside the insect, but its circulating titer should be under tight control. Then enzymes involved in JH metabolism, especially juvenile hormone esterases (JHEs) play critical roles in insect metamorphosis and reproduction. Within a set of 11 JHEs predicted in the diamondback moth (DBM) genome, Plutlla xylostella (Linn.) we identified one gene that contained the main functional motifs of insect JHEs. Its expression and transcript levels during egg, different instar of larvae, prepuae, pupae and adult stages were measured. Also, its expression in the epidermis, midgut and fatbody of the 4 th instar larvae was compared. The changes in enzyme activity in the 4th instar larvae were determined.

An endoparasitoid wasp, Cotesia plutellae, contains a polydnavirus called C. plutellae bracovirus (CpBV) and induces various physiological alterations of parasitized host along with expressions of viral genes. Two host translation inhibitory factors (HTIFs) encoded in CpBV specifically inhibit host mRNAs at post-transcriptional level. They are expressed in late larval stage of Plutella xylostella parasitized by C. plutellae. To understand their late expression control, promoter region of an HTIF gene called CpBV15α was cloned by inverse PCR. The cloned HTIF upstream region (1,113 bp) possessed a putative JH response element (JHRE) and other promoter elements. The putative promoter region was rejoined with an open reading frame of enhanced green fluorescence protein (EGFP). When the recombinant vector construct was injected into early third instar larvae of nonparasitized P. xylostella, it was expressed in fourth larval instar at 72 h after injection, compared to relatively early expression in 24 h after injection of control construct containing a baculovirus immediate-early promoter. However, recombinant EGFP construct lost the late expression pattern when its promoter region was incomplete by truncating JHRE region. PYR application inhibited EGFP expression of the recombinant construct, but gave little influence on truncated constructs. Interestingly, when the complete promoter construct was injected to pupal stage, its late expression pattern was lost and showed early expression pattern. However, an addition of PYR to pupae, which had been injected with the complete promoter construct, inhibited the reporter gene expression. These results suggest that late expression of a HTIF (CpBV15α) is controlled by its promoter, which is sensitive to host JH titer.

In this study, the toxic effects of fenoxycarb on biological traits of nontarger arthropod P. rosea, Collembola. The tests were assessed in the OECD artificial soil under two different exposure condtions, one was exposed in the bulk soil, and the other was exposed in the compacted soil which unidirectional force was applied to the soil surface. In the bulk system, survived adults and hatched juveniles were counted after 28-day exposures, and in the compact system, survived adults, eggs, hatched juveniles and molts were counted everyday until no more hatching. The toxic effect of fenoxycarb on survival and juvenile production of P. rosea in the bulk system was more toxic than that of the compact system. Juveniles and eggs were seriously affected as compared with toxic effect for adults. Particularly, toxic effect on hatching rate (3.75 mg/kg EC50juvenile) were very higher than that on oviposition (200.868 mg/kg EC50egg) or survival rate of adults ( >1200 mg/kg LC50). The molting freauency of P. rosea was decreased in a concentration dependent manner. These results suggest that the IGRs fenoxycarb exhibit significant impacts on the biological traits of non-target organisms P. rosea and its toxic effects are differently assessed depending on the exposure conditions.

꿀벌부채명나방 종령유충의 whole body에서 gel filtration 방법으로 유약호르몬 결합 단백질을 분리, 정제하였다. 분리된 단백질은 column chromatography법과 전기영동법에 의해 등가성을 확인하였다. 이 결합단백질은 전기 영동법에 의해 32K, gel filtration 에 의해 28K의 상대적 분자량을 나타냈다. 또한, JH III에 대한 해리도는 3.9M로 확인되었다.

몇가지 협력제의 7-ethoxy precocene II와 협력작용을 통한 활성증가와 작용기작을 구명하기 위하여 mikweed bug, Oncopeltus fasciatus 2령충에 항유약호르몬유사물과 협력제가 처리된 petri dish에 접종하여 생리활성 정도를 측정하였다. 얻어진 결과는 다음과 같다. 7-Ehtoxy precocene II의 반수활성농도는 g/이었다. 7-Ethoxy precocene II와 다른 산화저해제인 RO20-9747의 협력비가 14.05로 가장 높았고 그들의 반수활성농도는 이었다. 7-Ethoxy precocene II와 다른 협력제 1종, 2종, 4종을 조합을 달리하여 처리하였을 때 뚜렷한 협력작용 증가효과를 가져오지 못했다. 이상의 결과에서 다른 협력제들은 곤충의 방어기작을 알라타체를 포함하여 비선택적으로 저해하는 것으로 생각되었으나 RO20-9747은 7-ethoxy precocene II가 알라타체로 이행하는데 까지 곤충의 방어적 산화기작인 monooxygenase 활성을 선택적으로 저해함으로써 7-ethoxy precocene II가 알라타체로 이행량이 증가하여 활성증가를 가져온 것으로 생각되었다.

초 록 재래종 밤나무와 저항성 품종 밤나무(축파, 단택)에 기생하는 밤나무 혹벌의 유충에서 유약 호르몬과 유약호르몬 특이에스테라제의 활성도를 Gas liquid chromatohraphy (R ller et al.1965), Galleria cuticle wax 검사 (de Loof & van Loon 1981) 및 Liquid scintilation counter (Hammock & Sparks 1977)로 비교 측정한 결과는 다음과 같다. 유충에서 GLC로 분리한 유약호르몬은 양군 모두에서 유약호르몬 I(JH-I)로 동정되었다. 저항성 품종(축파, 단택)에 기생하는 밤나무 혹벌의 유약호르몬 함량은 35,800 GU/g와 30,900 GU/g이고, 재래종에 기생하는 밤나무 혹벌의 유약호르몬의 함량은 28,600 GU/g으로 나타났다. 유약호르몬 특이 에스테라제 활성도는 저항성 품종(축파, 단택)에 기생하는 밤나무 혹벌은 1.48 n mole/min/ml와 1.63 n mole/min/ml, 그리고 재래종에 기생하는 밤나무 혹벌은 1.89 n mole/min/ml로 측정되었다. 유약호르몬 함량은 재래종 밤나무에 기생하는 밤나무 혹벌보다 저항성 밤나무(축파, 단택)에 기생하는 밤나무 혹벌에서 더 높았으나, 유약호르몬 특이에스테라제 활성도는 저항성 밤나무(축파, 단택)보다 재래종 밤나무에 기생하는 혹벌에서 더 높게 나타나 서로 역비례 경향을 나타냈다.

본연구는 오리나무잎벌레(Agelastica coerulea Baly)성충의 유면 유기에 미치는 온도와 광주기 영향 및 유약호르몬(juvenile hormome III)과 탈피호르몬(20-hydroxyecdysone)이 휴면중인 성충에 미치는 영향을 조사하기 위하여 수행되었다. 오리나무잎벌레는 일년에 일회 발생하며 난, 유충, 용 성충기간은 가각 7~10일, 19~21일, 14~15일, 약 10개월로 조사되었다. 오리나무잎벌레의 알과 유충을 와 의 조건에서 광주기를 각각 16L/8L, 12L/12D, 8L/16D로 달？여 사육하여도 모든 성충이 휴면에 들어가 이들은 필수성충휴면을 하는 것으로 생각되었다. 휴면기간동안 난소는 거의 발육되지 않았으며 유면말기의 개체를 , 16L/8D에 노출시키면, 난소소관이 급속하게 발달되었다. 휴면중인 성충에 유약호르몬을 처리하면 일시적으로 휴면이 타파되고 산란이 이루어졌으나 탈피호르몬은 아무런 영향도 미치지 못했다.