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An entomopathogenic bacterium, Xenorhabdus nematophila, inhibits the expression of an antibacterial peptide, cecropin, of the beet armyworm, Spodoptera exigua.
J Insect Physiol. 2004 Jun; 50(6):489-96.JI

Abstract

An entomopathogenic bacterium, Xenorhabdus nematophila, is known to depress hemocyte nodule formation of target insects by inhibiting eicosanoid biosynthesis. This study analyzed the inhibitory effect of X. nematophila on the humoral immunity of the target insects and tested its association with the host eicosanoid pathway. Plasma collected from the fifth instar larvae of Spodoptera exigua, when they were injected with X. nematophila, did not show antibacterial activity against Escherichia coli by a growth inhibition zone assay. In comparison, heat-killed X. nematophila induced significant antibacterial activity in the plasma. The antibacterial humoral activity was further demonstrated by examining a specific potent antibacterial peptide, cecropin. Two cecropin genes ('A' and 'B') were partially cloned from the fifth instar larvae of S. exigua by conserved degenerate primers using nested reverse transcriptase-polymerase chain reaction (RT-PCR). They showed high homologies with known cecropins from other lepidopteran species. Northern analysis using the cecropin probe showed that the injection of the heat-killed X. nematophila induced significant expression of a cecropin mRNA transcript (approximately 1.1 kb), but the larvae injected with the live bacteria did not show the corresponding transcript. Injection of arachidonic acid did not rescue the inhibition of X. nematophila based on either antibacterial activity or cecropin gene expression. The addition of dexamethasone, a specific phospholipase A2 inhibitor, did not inhibit antibacterial activity or cecropin gene expression when the larvae were injected with heat-killed X. nematophila. These results suggest that X. nematophila inhibits the antibacterial humoral immune reaction as well as the cellular immune reaction in S. exigua and that the inhibition of X. nematophila on the expression of the antibacterial peptide is not associated with inhibition of the eicosanoid pathway.

Authors+Show Affiliations

Department of Agricultural Biology, Andong National University, Songchun-Dong 388, 760-749, South Korea.No affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

15183278

Citation

Ji, Dongjin, and Yonggyun Kim. "An Entomopathogenic Bacterium, Xenorhabdus Nematophila, Inhibits the Expression of an Antibacterial Peptide, Cecropin, of the Beet Armyworm, Spodoptera Exigua." Journal of Insect Physiology, vol. 50, no. 6, 2004, pp. 489-96.
Ji D, Kim Y. An entomopathogenic bacterium, Xenorhabdus nematophila, inhibits the expression of an antibacterial peptide, cecropin, of the beet armyworm, Spodoptera exigua. J Insect Physiol. 2004;50(6):489-96.
Ji, D., & Kim, Y. (2004). An entomopathogenic bacterium, Xenorhabdus nematophila, inhibits the expression of an antibacterial peptide, cecropin, of the beet armyworm, Spodoptera exigua. Journal of Insect Physiology, 50(6), 489-96.
Ji D, Kim Y. An Entomopathogenic Bacterium, Xenorhabdus Nematophila, Inhibits the Expression of an Antibacterial Peptide, Cecropin, of the Beet Armyworm, Spodoptera Exigua. J Insect Physiol. 2004;50(6):489-96. PubMed PMID: 15183278.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - An entomopathogenic bacterium, Xenorhabdus nematophila, inhibits the expression of an antibacterial peptide, cecropin, of the beet armyworm, Spodoptera exigua. AU - Ji,Dongjin, AU - Kim,Yonggyun, PY - 2003/12/26/received PY - 2004/03/05/revised PY - 2004/03/08/accepted PY - 2004/6/9/pubmed PY - 2004/11/5/medline PY - 2004/6/9/entrez SP - 489 EP - 96 JF - Journal of insect physiology JO - J Insect Physiol VL - 50 IS - 6 N2 - An entomopathogenic bacterium, Xenorhabdus nematophila, is known to depress hemocyte nodule formation of target insects by inhibiting eicosanoid biosynthesis. This study analyzed the inhibitory effect of X. nematophila on the humoral immunity of the target insects and tested its association with the host eicosanoid pathway. Plasma collected from the fifth instar larvae of Spodoptera exigua, when they were injected with X. nematophila, did not show antibacterial activity against Escherichia coli by a growth inhibition zone assay. In comparison, heat-killed X. nematophila induced significant antibacterial activity in the plasma. The antibacterial humoral activity was further demonstrated by examining a specific potent antibacterial peptide, cecropin. Two cecropin genes ('A' and 'B') were partially cloned from the fifth instar larvae of S. exigua by conserved degenerate primers using nested reverse transcriptase-polymerase chain reaction (RT-PCR). They showed high homologies with known cecropins from other lepidopteran species. Northern analysis using the cecropin probe showed that the injection of the heat-killed X. nematophila induced significant expression of a cecropin mRNA transcript (approximately 1.1 kb), but the larvae injected with the live bacteria did not show the corresponding transcript. Injection of arachidonic acid did not rescue the inhibition of X. nematophila based on either antibacterial activity or cecropin gene expression. The addition of dexamethasone, a specific phospholipase A2 inhibitor, did not inhibit antibacterial activity or cecropin gene expression when the larvae were injected with heat-killed X. nematophila. These results suggest that X. nematophila inhibits the antibacterial humoral immune reaction as well as the cellular immune reaction in S. exigua and that the inhibition of X. nematophila on the expression of the antibacterial peptide is not associated with inhibition of the eicosanoid pathway. SN - 0022-1910 UR - https://www.unboundmedicine.com/medline/citation/15183278/An_entomopathogenic_bacterium_Xenorhabdus_nematophila_inhibits_the_expression_of_an_antibacterial_peptide_cecropin_of_the_beet_armyworm_Spodoptera_exigua_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S0022191004000368 DB - PRIME DP - Unbound Medicine ER -