title: Benzylideneacetone, an immunosuppressant, enhances virulence of Bacillus thuringiensis against beet armyworm (Lepidoptera: Noctuidae).
abstract: Benzylideneacetone (BZA) is a metabolite of gram-negative entomopathogenic bacterium Xenorhabdus nematophila, and it acts as an enzyme inhibitor against phospholipase A2 (PLA2). PLA2 catalyzes a committed biosynthetic step of eicosanoids, which mediate insect immune reactions to infection by microbial pathogens. This study tested a hypothesis that a putative immunosuppressive activity of BZA may enhance virulence of Bacillus thuringiensis against the fifth instars of Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae). In in vitro conditions, BZA significantly inhibited hemocyte microaggregation induced by B. thuringiensis and impaired hemocyte-spreading behavior of S. exigua in a dose-dependent manner. Oral administration of BZA gave similar immunosuppressive effect on the hemocytes of the fifth instars. Although BZA itself did not possess any insecticidal activity on oral administration, when BZA was treated in a mixture with a low dose of B. thuringiensis spp. aizawai to fifth instars, the bacterial virulence was significantly enhanced. BZA also enhanced virulence of B. thuringiensis spp. kurstaki, which alone was of limited effectiveness against S. exigua. This study suggests that an immunosuppression by BZA is positively linked to potentiation of B. thuringiensis.
authors.affiliation: Department of Bioresource Sciences, Andong National University, Andong 760-749, Korea.
authors.forename: Bowon
authors.initials: B
authors.lastname: Kwon
authors.forename: Yonggyun
authors.initials: Y
authors.lastname: Kim
mesh_terms: D000284:Administration, Oral; D000818:Animals; D001413:Bacillus thuringiensis / Q000187:drug effects / Q000472:pathogenicity*; D002074:Butanones / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006434:Hemocytes / Q000187:drug effects; D007166:Immunosuppressive Agents / Q000494:pharmacology*; D010572:Pest Control, Biological; D010741:Phospholipases A / Q000037:antagonists & inhibitors* / Q000378:metabolism; D018411:Spodoptera / Q000201:enzymology / Q000254:growth & development* / Q000276:immunology; D014774:Virulence / Q000187:drug effects
chemical_list: D002074:Butanones; D004791:Enzyme Inhibitors; D007166:Immunosuppressive Agents; C025383:benzylideneacetone; D010741:Phospholipases A