국내 배추좀나방(Plutella xylostella) 집단은 피레스로이드 농약에 대해서 저항성을 보이며, 이는 이 살충제의 작용점인 소듐이온채널 유전자의 돌연변이에 기인된다. 더욱이 배추좀나방은 대부분 상용화된 살충제에 대해서 저항성을 발달시킬 수 있다. 본 연구는 배추좀나방을 효과적으로 방제하기 위해 내부기생성 천적인 프루텔고치벌(Cotesia plutellae)과 미생물농약인 Bacillus thuringiensis의 혼합처리 기술을 개발하기 위해 수행되었다. 프루텔고치벌이 감수성과 저항성 배추좀나방에 대한 기생 선호성에 차등이 있는 지 조사하기 위해 다섯 개 서로 다른 집단에 대해서 살충제 감수성과 프루텔고치벌 기생성 차이를 비교하였다. 이들 배추좀나방 집단들은 피레스로이드, 유기인계, 네오니코틴계 및 곤충성장조절제를 포함하는 세 종류의 상용 살충제에 대한 약제 감수성에서 뚜렷한 차이를 보였다. 그러나 이들 집단들은 프루텔고치벌에 의한 기생률에서는 차이를 보이지 않았다. 더욱이 기생된 배추좀나방은 B. thuringiensis에 대해서 감수성이 증가되었다. 프루텔고치벌이 갖는 면역억제인자 가운데 바이러스 유래 ankyrin 유전자(vankyrin)를 비기생된 배추좀나방에 발현시켰다. Vankyrin의 발현은 배추좀나방 3령충의 B. thuringiensis에 대한 감수성을 현격하게 증가시켰다. 즉, 프루텔고치벌에 의해 야기된 면역저하가 B. thuringiensis의 살충력을 증가시켰다. 이러한 결과들은 프루텔고치벌과 미생물농약인 B. thuringiensis의 혼합처리가 살충제 저항성 배추좀나방을 효과적으로 방제할 수 있다고 제시하고 있다.

Polydnaviruses (PDVs) are a group of insect double stranded DNA viruses and symbiotically associated with host endoparasitoid wasps. Their segmented genome is located in host chromosome(s) in a proviral form. Viral replication is initiated at the ovary during late pupal stages. Little is known about the factors involved in the viral replication. This study analyzed the ovarian transcripts of an endoparasitoid wasp, Cotesia plutellae, by 454 pyrosequencing and subsequent gene annotation. Out of 2,226 contigs and 12,457 singletons, 50 transcripts categorized in DNA replication, coat proteins, and viral origins were selected as putative viral replication factors. The selected genes were analyzed in their expressions according to host wasp development. Quantitative real-time RT-PCRs showed that some of the selected genes were expressed during the viral replication at late pupal stage. Using RNA interference, five putative genes were tested in their implication in the viral replication by analyzing viral DNA amplification, structure of ovarian calyx, and parasitism. RNA interference of contig#1004 (broad complex) or contig#174 (a viral DNA polymerase gene) significantly inhibited DNA amplification without any impairment of viral formation, and subsequently resulted in significant reduction in the wasp parasitism. This study reports that two wasp genes (or not encapsidated viral genes) are implicated in the viral DNA amplification and viral coat protein production during the polydnaviral replication.

DNA in the eukaryotic nucleus is packaged into highly organized chromatin. The basic structural unit of chromatin is the nucleosome, which consists of approximately 146 base pairs of DNA wrapped around a histone octamer core containing two molecules each of core histones H2A, H2B, H3, and H4. Histone covalent modification at the protruding N-terminal region from the nucleosomal core can change the chromatin conformation in order to regulate gene expression. A viral H4 was found in the genome of Cotesia plutellae bracovirus (CpBV). The obligate host of the virus is an endoparasitoid wasp, C. plutellae, which parasitizes the diamondback moth, Plutella xylostella, and interrupts host development and immune reactions. CpBV-H4 has been regarded as an immunosuppressive gene. Its extended N-terminal region contains nine lysine residues which are the target for modification. Previous report showed that CpBV-H4 inhibited hemocyte-spreading after transient expression. Here, transient expression of truncated CpBV-H4 (without N-terminal region) did not show high inhibitory effects on hemocyte-spreading. Moreover, the truncated CpBV-H4 induced acetylation of nucleus histone H4. Host H4 was found to be decreased in transcription after parasitization compared to nonparasitized larvae. Atransient expression of CpBV-H4 significantly inhibited host H4 transcription, suggesting a role of CpBV-H4 in controlling gene expression. Point mutagenesis study showed that two lysines (K6 and K16) of CpBV-H4 were found to have high inhibitory effects on hemocyte spreading. These results indicate the importance of CpBV-H4 and its N-terminal region to control gene expression and suppress host immunity.

Reproductive incompatibility is an important factor to select a specific biological control agent for successful augmentation of the corresponding endogenous population. An endoparasitoid, Cotesia plutellae (Kurdjumov), is an effective control agent to diamondback moth, Plutella xylostella (L.) and has been known to be classified into two groups in terms of reproductive incompatibility. This study analyzed an Korean population of C. plutellae in terms of morphological characters and mitochondrial DNA marker, which did not match with either of two reproductive incompatibility groups. These results suggest that a Korean population of C. plutellae can be involved in a novel reproductive group. For any augmentation program of C. plutellae in Korea, reproductive incompatibility should be seriously considered to select a particular exotic population.

아메리카잎굴파리의 내부기생봉인 Neochrysocharis formosa의 산란과 기주체액섭취 선호성을 조사하였다. N. formosa는 기주유충의 몸 뒤쪽에 대부분 산란하였다. 온도 조건에 따른 일산란수와 일기주체액섭취수를 조사한 결과 온도가 높을수록 증가하는 경향이었으며 15, 20, 25, 3에서의 산란수와 체액섭취수의 비율은 각각 0.5, 0.9, 1.0, 1.0이었다. 항온조건하에서 N. formosa의 총산란수와 기주체액섭취수는 각각 176개 188.7개이었으며 산란수와 기주체액섭취수 비율은 0.9이었고 암컷 수명은 11.8일이었다. 산란과 기주체액섭취는 주로 아메리카잎굴파리 3령유층을 선호하였다.