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Fatty acid composition of immune-associated tissues of Spodoptera exigua
Jiyeong Park,Yonggyun Kim 한국응용곤충학회 2013 한국응용곤충학회 학술대회논문집 Vol.2013 No.10
Immune mediators play crucial roles in amplifying the emergency signals with massive amounts of de novo synthesized mediators and relaying the specific recognition signals to the immune-associated target tissues. Eicosanoids are the representative immune mediators and synthesized from a polyunsaturated fatty acid (PUFA), arachidonic acid. Compared to mammalian systems, insects have relatively low levels of arachidonic acid in the biological membranes. This has raised a fundamental issue that eicosanoids may be not significant in insect system. Our previous chemical analysis suggests that the hemocytes of Spodoptera exigua have less than 5% arachidonic acid. We postulated that S. exigua may store arachidonic acid in other tissues, such as fat body. This analysed fatty acid compositions of two immune-associated tissues using a gas chromatography (GC) eguipped with FID detector or GC-MS. Our analysis of PUFA in the immune tissues suggests that insects maintain a low level of PUFA including arachidonic acid due to its evolutionary origin from the paleozoic era at which the oxygen level was 35%, compared to the present era 21%.
Biological Control of Meloidogyne hapla Using an Antagonistic Bacterium
Park, Jiyeong,Seo, Yunhee,Kim, Young Ho The Korean Society of Plant Pathology 2014 Plant Pathology Journal Vol.30 No.3
We examined the efficacy of a bacterium for biocontrol of the root-knot nematode (RKN) Meloidogyne hapla in carrot (Daucus carota subsp. sativus) and tomato (Solanum lycopersicum). Among 542 bacterial isolates from various soils and plants, the highest nematode mortality was observed for treatments with isolate C1-7, which was identified as Bacillus cereus based on cultural and morphological characteristics, the Biolog program, and 16S rRNA sequencing analyses. The population density and the nematicidal activity of B. cereus C1-7 remained high until the end of culture in brain heart infusion broth, suggesting that it may have sustainable biocontrol potential. In pot experiments, the biocontrol efficacy of B. cereus C1-7 was high, showing complete inhibition of root gall or egg mass formation by RKN in carrot and tomato plants, and subsequently reducing RKN damage and suppressing nematode population growth, respectively. Light microscopy of RKN-infected carrot root tissues treated with C1-7 showed reduced formation of gall cells and fully developed giant cells, while extensive gall cells and fully mature giant cells with prominent cell wall ingrowths formed in the untreated control plants infected with RKNs. These histopathological characteristics may be the result of residual or systemic biocontrol activity of the bacterium, which may coincide with the biocontrol efficacies of nematodes in pots. These results suggest that B. cereus C1-7 can be used as a biocontrol agent for M. hapla.
( Jiyeong Park ),( Seunghyun Baek ) 21세기영어영문학회 2021 영어영문학21 Vol.34 No.1
This study explored the choice of definite the and demonstrative that across direct and associative anaphoric contexts in fifty-six L1-Korean L2-English learners and twenty-eight native speakers of English (NSE) as a reference group. The L2-English participants were divided into two groups on the basis of their grammatical proficiency as measured by a cloze test. Additionally, L1-Korean and L2-English forced-choice elicitation tasks were conducted to examine how they choose L1 and L2 determiners across the distinctive anaphoric contexts. The results showed that the NSEs highly preferred the across all contexts. Meanwhile, in the direct anaphoric contexts, the L1-Korean L2-English learners exclusively preferred ku in their L1 and the in their L2 regardless of their L2 grammatical proficiency, properly mapping ku onto the. In the associative anaphoric contexts, they dominantly preferred the zero article in their L1, but the low-proficient L2 learners chose the much less often than the high-proficient ones, demonstrating their fluctuant choice between the and that. These results suggest that the low-proficient L2 learners undergo great difficulties in distinguishing the and that in contexts where implicit antecedents emerge, improperly mapping the zero article in their L1 onto either the or that in their L2. The possible linguistic reasons for their unstable choice and pedagogical implications were further discussed.
A Small G Protein, Rac1, Activates Hemocyte Spreading Behavior in Response to immune Mediators
Jiyeong Park,Yonggyun Kim 한국응용곤충학회 2012 한국응용곤충학회 학술대회논문집 Vol.2012 No.10
Insect blood cells, hemocytes, inhibit spreading behavior upon bacterial challenge to perform cellular immune responses. Hemocyte spreading is accomplished by cytoskeleton rearrangement, which is activated by various immune mediators, such as biogenic monoamins, plasmatocyte-spreading peptide(psp), and eicosanoids. However, little is known how these, immune mediators. acitvate hemocyte spreading behavior. A small G protein, Rac1, gene was identified in hemocytes of Spodoptera exiqua. Its expressed in most developmental stages accept egg and expecially expresses in hemocytes and fat body of Larval stage. In response to bacterial challenge, its expression was segnificantly up-regulated. However, RNA inteference (RNAi) of Rac1 expression inhibited hemocyte spreading behavior. under RNAi condition of Rac1, octopamine and psp failed to activate hemocyte spreading behavior. Interestingly, as addition of prostaglandinE2 to the RNAiconditioned Larval rescued the mediation of octopamine and psp. These results indicate that Rac1 is required for mediation of octopamine and psp on hemocytespreading behavior and suggest that Rac1 may activate eicosanoid biosnthesis.
Eicosanoids Modulate Hemocyte Polulation in Response to Immune Challenge in Spodoptera exigua
Jiyeong Park,Yonggyun Kim 한국응용곤충학회 2012 한국응용곤충학회 학술대회논문집 Vol.2012 No.05
As the immune reactions in human white blood cells of certain substances from insects to defend it when invaded by immune blood cells is increased. We experiment with changes in the total number of blood cells through the blood cells which increases and decreases, as well as to observe whether the immune response through any route is to evaluate what happens. Hemocyte population was analyzed in the last instar larvae of Spodoptera exigua. Granulocyte and plasmatocyte were predominant (>75%) types of hemocytes, whereas spherulocyte, prohemocyte, and oenocytoid hemocytes were observed in small densities (5~10%). Total hemocyte counts (THCs) were varied among different ages (day1-day5) of the last instar, in which day 3 larvae (L5D3) had the maximal density. Upon bacterial challenge to L5D3 larvae, THC was further enhanced within 2 h and then decreased to background level. This rapid THC increase in response to bacterial challenge was inhibited by injection with dexamethasone (1 ㎍ per larva). However, the addition of arachidonic acid reversed the inhibitory activity of dexamethasone and allowed the larvae to increase THC. This THC increase was mediated by cyclooxygenase products, but not by lipoxygenase products.
Jiyeong Park,Yonggyun Kim 한국응용곤충학회 2013 한국응용곤충학회 학술대회논문집 Vol.2013 No.04
Immune defense is indispensible for insect survival. However, uncontrolled and excessive immune responses would be highly detrimental and energy-consuming processes. An insect cytokine, plasmatocyte-spreading peptide (PSP), induces hemocyte-spreading behavior as well as activating phenoloxidase (PO) in the beet armyworm, Spodoptera exigua. A hemocyte transcriptome of S. exigua contains a partial sequence of a putative PSP-binding protein (SePSP-BP). SePSP-BP was expressed in all developmental stages especially in hemocytes and fat body. A quantitative RT-PCR showed that the bacterial infection significantly up-regulated the expression level of SePSP-BP. A double-stranded RNA specific to SePSP-BP (dsRNASePSP-BP) was injected and suppressed SePSP-BP expression even in response to bacterial challenge. The larvae treated with dsRNASePSP-BPsuffered high mortality to infection of nonpathogenic bacteria and prolonged high PO activity after the immune challenge. These results suggest that SePSP-BP may play a role in suppressing immune responses as a negative controller