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Park Youngjin,Choi Yonghwa,Kim Yonggyun Korean Society of Applied Entomology 2005 Journal of Asia-Pacific Entomology Vol.8 No.2
Entomopathogenic nematode, Steinernema carpocapsae, carries the symbiotic bacterium, Xenorhabdus nematophita, and enter host insect hemocoel. In the infected host, nematodes release the bacteria, which in turn cause lethal hemolymph septicemia. This study was designed to test a hypothesis that hemolymph septicemia of beet armyworm, Spodoptera exigua, is triggered by X. nematophita through a programmed cell death (=apoptosis) of the hemocytes. Morphological changes of the hemocytes after the bacterial infection were similar to cell changes undergoing a typical apoptosis. At 4-8 h post-infection, the cell membrane blebbing and apoptotic vesicles were observed and the nuclear membrane was broken apart. At 12 h post-infection, the overall cell shape was lost externally and nuclear condensation was evident internally, where genomic DNA was fragmented into small pieces. Proportion of apoptotic hemocytes increased with post-infection time and reached a maximum level when the hemocytes were in complete septicemia. Increase of FAD-glucose dehydrogenase (EC 1.1.99.10) activity preceded initial hemocyte apoptosis after the bacterial infection. The infected plasma or the culture broth of X. nematophila contained apoptosis-inducing factors. The apoptosis factors were extracted into organic fraction and turned out to be relatively high hydrophobic chemical nature after further fractionation assay. These results indicate that X. nematophita induces hemocyte apoptosis by its secretory material(s), which lead to hemolymph septicemia and immunodepression of the target insect hosts.
Cadherin PxCad1 is a Functional Receptor for Cry1Ac Toxicity in Plutella xylostella
Youngjin Park,Yonggyun Kim 한국응용곤충학회 2014 한국응용곤충학회 학술대회논문집 Vol.2014 No.10
Six of cadherins have been selected from the P. xylostella genome 52 open reading frames are annotated as cadherin-like genes. Compared to other 5 cadherins of P. xylostella (PxCads), PxCad1 has the highest homology with other lepidopteran insect cadherins and PxCad1 was expressed in all developmental stages specially in gut tissue. Expression of PxCad1 was suppressed by feeding its specific double-stranded RNA (dsRNA, 150ng/larva) and treatment of dsPxCad1 significantly reduced susceptibility to Bt Cry1Ac toxin. To confirm the specific interaction between PxCad1 and Cry1Ac, a toxin-binding assay was performed using enzyme-linked immunosorbent assay (ELISA). The ELISA indicates that BBMV extracted from PxCad1-silenced P. xylostella have significantly lower binding activity to active form of Cry1Ac than control BBMV. Moreover, the analysis of the binding parameters showed that the toxin affinity (Kd) of the control BBMV extract (BBMV-dsCON) was 6.08 ± 0.84 nM, which was not much different to the affinity value (6.72 ± 0.81 nM) of the dsPxCad1 treatment. However, there was a remarkable difference in number of binding sites (Bmax), in which BBMV-dsCON extract had 1.61 ± 0.04, but the BBMV-dsPxCad1 extract had 0.88 ± 0.02. Taken together, these results are suggest that PxCad1 is a functional receptor for Cry1Ac toxicity against P. xylostella larva.
Youngjin Baek,Gwigeun Park,Dongmin Park,차헌녕,김흥근 전력전자학회 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.6
A new method for reducing the common-mode current generated by the voltage variations in a two-inverter air conditioner system by applying a synchronized pulse-width modulation (PWM) strategy is proposed. The PWM signals of the master-mode inverter are generated based on the reference voltage, while those of the slave-mode inverter are output in the opposite direction when the master-mode inverter changes its switching state. However, the slave-mode control results in a mismatch between the reference voltage and the actual output voltage that is modified by synchronized control operation. The proposed method is capable of reducing and controlling this voltage error by performing signal selection in the vector space of the slave-mode inverter, which mitigates the distortion of the phase current. The efficacy of this method in reducing conducted emissions has been validated both theoretically and experimentally.
Cellular immunosenescence in adult male crickets, <i>Gryllus assimilis</i>
Park, Youngjin,Kim, Yonggyun,Stanley, David Wiley Subscription Services, Inc., A Wiley Company 2011 Archives of Insect Biochemistry and Physiology Vol.76 No.4
<P><B>Abstract</B></P><P>Ecological immunity studies in invertebrates, particularly insects, have generated new insights into trade‐offs between immune functions and other physiological parameters. These studies document physiologically directed reallocations of immune costs to other high‐cost areas of physiology. Immunosenescence, recognized as the age‐related deterioration of immune functions, is another mechanism of radically altering immune systems. We investigated the hypothesis that aging brings on immunosenescence in adult males of the cricket, <I>Gryllus assimilis.</I> Our data show that the intensity of melanotic nodule formation decreased with adult age from after 3‐week post‐adult emergence. Circulating hemocyte populations similarly decreased from about 5,000 hemocytes/<I>µ</I>l hemolymph to about 1,000 hemocytes/<I>µ</I>l hemolymph. The numbers of damaged hemocytes in circulation increased from less than 10% at 1‐week post‐adult emergence to approximately 60% by 3‐week post‐adult emergence. The composition of hemocyte types changed with age, with increasing proportions of granulocytes and decreasing proportions of plasmatocytes. The declines in nodule formation were not linked to the adult age of sexual behaviors, which begin shortly after entering adulthood in this species. We infer that age‐related senescence, rather than cost reallocations, may account for observed declines in various parameters of immune functions in insects, as seen in other animals. © 2011 Wiley Periodicals, Inc.</P>
Genes Associated with Glycerol Biosynthesis in the Red-spotted Apollo Butterfly, Parnassius bremeri
Youngjin Park,Yonggyun Kim,Kang-Woon Lee 한국응용곤충학회 2015 한국응용곤충학회 학술대회논문집 Vol.2015 No.04
The red-spotted apollo butterfly, Parnassius bremeri, immatures grow during winter and spring. Supercooling point of larvae during January goes much below -20℃. Morphologically, the larvae appear to be adapted to cold temperatures. Dark-colored body surface is useful to absorb solar energy and spiny integument may prevent any external ice formation on the body surface. Biochemically, P. bremeri larvae elevate glycerol as a cryoprotectant. This study reports two genes associated with glycerol biosynthesis in P. bremeri. Larval transcripts were analyzed using RNA-Seq technique. A total of 14 Gb transcripts were read by Illumina HiSeq and assembled to be 127,279 contigs. To specify the the genes associated with glycerol biosynthesis, a biosynthetic pathway to synthesize glycerol from dihydroxyacetone-3-phosphate was predicted with two genes of glycerol-3-phosphate dehydrogenase (GPDH) and glycerol kinase (GK). Both genes were annotated in the transcriptome of P. bremeri. Pb-GPDH encodes 166 amino acid residues containing NAD+-binding region, catalytic site, and calcium binding region. The predicted amino acid sequence was clustered with other lepidpopteran GPDH genes. Three Pb-GK genes were annotated from the transcriptome. Pb-GK1 encodes a full open reading frame of 514 amino acid residues. A ohylogenetic analysis showed that these three GKs were separately clustered. Interestingly, Pb-GK1 was clustered with other GKs that were known to be associated with rapid cold hardiness.
Park Youngjin,Vatanparast Mohammad,Minoo Sajjadian Seyedeh 한국응용곤충학회 2022 Journal of Asia-Pacific Entomology Vol.25 No.2
The red imported fire ant (RIFA), Solenopsis invicta, is one of the globalized invasive pests. This study focused on pathogenicity and virulence of entomopathogenic fungi as one of the biological control agents to RIFA workers under different temperatures. The fungal pathogen, Beauveria bassiana ANU1 was isolated from Korea in 2015 and showed the pathogenicity to RIFA workers. A conidial suspension (1 × 10 7 conidia/ml) induced a low mortality from day 2 after treatment and reached to 100% mortality at day 7 and day 8 after treatment for major and minor workers, respectively. The median lethal concentrations of B. bassiana ANU1 were calculated as 3.9 × 10 3 for major and 4.6 × 10 3 for minor workers at day 7 after treatment. Low temperatures decreased a virulence of B. bassiana ANU1 (1 × 10 7 conidia/ml) to RIFA and showed mortality of 26.6% for major and 20% for minor workers. Based on bioassay results, this study provides one of possibilities of effective and successful strategy for controlling RIFA by entomopathogenic fungi.
Insect Immunity (Insect host-Pathogen Interaction)
Youngjin Park 한국응용곤충학회 2019 한국응용곤충학회 학술대회논문집 Vol.2019 No.04
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.