It is well known that invertebrates do not have adaptive immunity because of their short life cycle. Especially, insects have a strong innate immune system, including antimicrobial peptides (AMPs) production, to protect themselves from a wide range of pathogens. Previously, we identified over 60 genes related to AMP production, including Toll and Imd pathways, and characterized their immunological role in response to pathogenic infection through target gene-specific RNAi. This resulted in decreased expression levels of most AMPs in the larvae which were injected with target gene-specific dsRNA and microbes. Currently, we are focusing on studying the regulation of AMP production through epigenesis. It may help us understand how to regulate the innate immune system induced by pathogenic infection.

Since the importance of integrated pest management to minimize environmental damage and maximize pest control effectiveness has emerged, efforts to put it into practice have continued. To implement IPM, it is necessary to estimate the economic injury level to determine the control method by identifying pests and weeds that damage the quantity and quality of crops in the field, investigating the occurrence level, and calculating the ratio of cost and effectiveness. Also, damage to host plants caused by increased density of insect pests appears to change plant’s health that key factor for managing crops. Therefore, understanding the relationship between the density of pests and the damage to the host plants is necessary. This study aims to analyze the causal relationship between the density of insect pests and damage to the host plants for estimating the economic injury level of insect pests on the host plants and investigating the possibility of pest control decision-making using plant health status.

곤충면역학은 주로 위생해충인 모기와 말라리아 (또는 Wolbachia)를 중심으로 많은 연구가 이뤄졌으며, 농업해충분 야에서는 곤충병원선충, 기생봉, Polydnavirus, 백강균, Bt 등에 대한 기주곤충과의 상호작용 연구가 기주면역저하와 관련한 생물적방제 인자에 대한 대안으로써 진행되고 있다. 이 가운데, 세균이 생성하는 Bt와 같은 내독소단백질은 기주곤충의 중장에 존재하는 수용체(cadherin, aminopeptidase N, alkaline phosphatase)와의 상호작용으로 기주에 대한 살충효과가 나타는 것을 설명하고 있으며, 최근에는 막관통단백질인 ATP-binding cassette transporter (ABC transporter)는 해독작용과 더불어 Bt와 수용체간의 상호작용에 관여하고 있음이 조명되고 있다. 따라서 곤충의 ABC transporter에 대한 생리적 기능 구명은 기주곤충과 병원체 상호작용 연구의 새로운 장으로 조명될 수 있을 것이다.

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.

Five phaP family genes and one phaR gene have been identified in the genome of Burkholderia gut symbiont. PhaP proteins function as surface proteins of polyhydroxyalkanoate (PHA) granules, and PhaR protein acts as a negative regulator of PhaP biosynthesis. To address the biological roles of four phaP family genes (phaP1, phaP2, phaP3, and phaP4) and the phaR gene during insect-gut symbiont interaction, these Burkholderia mutants were fed to the second instar nymph. The ΔphaR mutant decreased the colonization ability in the host midgut compared to wild-type Burkholderia cells and negatively affected the host insect’s fitness compared with wild-type infected host. These results demonstrate that PhaR plays an important role in the biosynthesis of PHA granules and it is significantly related to the colonization of the Burkholderia gut symbiont in the host insects’ midgut

Based on climate change scenario, local distribution of insect pest population should be changed in near future as well as their host. Even though well defined insect geographical distribution model is developed and projected its potential establishment in Korea under climate change scenario, it has defectiveness without geographical matching of its host. SADIE (spatial analysis with distance indices) allows improved interpretation of the spatial associations between two populations within a given sampling area because it is designed for data that are distributed in discrete areas with relatively well-defined boundaries, and measures the extent of clustering with subsequent testing for spatial patterns in relationships among sample locations. In this study, we calculated and analyzed the spatial association between the Ecoclimatic Index (EI) of light brown apple moth, Epiphyas postvittana, using CLIMEX, and projected farm land suitability of apple trees for the possibility of shift and matching geographical location of insect-host relationship under climate change scenario in Korea.

곤충병원세균이 효과적으로 병원력을 발휘하는 데 대상 곤충의 면역저하가 요구될 수 있다. 본 연구는 대상곤충의 면역저하가 병원세균의 살충능력에 직접 연관된다는 가설을 세웠다. 곤충병원세균을 5령 누에(Bombyx mori)의 혈강에 접종하였을 때, X. nematophilus는 다른 곤충병원세균인 Staphyiococcus gallinarum 보다 1,200배 높은 병원력을 보였다. 비록, 두 곤충병원세균은 누에의 혈구세포에 대해서 독성효과를 가지고 있지만, X. nematophiius는 S. gallinarum과 비교해보다 빠르고 높은 세포독성 영향을 보였다. 세포성 면역반응에서 5농도로 세균이 접종되었을 때, 누에는 약 20개 정도의 소낭을 형성하였다. 특히, 살아있는 X. nematophilus가 접종된 누에에서 소낭 형성은 크게 감소하였지만, S. gullinarum은 소낭 형성 감소에 영향을 주지 않았다. 두 세균 모두는 prophenoloxidase (proPO)의 활성화를 억제시켰다. 그러나 X. nematophilus.가 S. gallinarum보다 높게 PO 활성화를 억제시켰다. 라이소자임의 활성유도는 S. gallinarum접종 후 4시간에서 관찰되었으나, X. nematophilus를 접종하였을 때는 라이소자임의 활성이 전혀 관찰되지 않았다 이러한 결과들은 누에에서 X. nematophilus가 S. gallinarum보다 더 큰 면역저하를 유발하여 병원성을 높였다는 것을 보여준다. 따라서 본 연구는 곤충병원세균에 의해서 유발된 면역저하는 곤충병원세균의 병원성과 연관되어 있다는 것을 제시한다.다.