Nodulation Reaction to Fungal Infections in Larvae of Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae) Mediated by Eicosanoids

Authors : Hasan TUNAZ, Cemil BENGİN, Mehmet Kubilay ER

Pages : 11-18

View : 12 | Download : 6

Publication Date : 2008-01-01

Article Type : Research Paper

Abstract :Injecting larvae of the Colorado potato beetle, Leptinotarsa decemlineata insert ignore into journalissuearticles values(Say); insert ignore into journalissuearticles values(Coleoptera: Chrysomelidae);, with eicosanoid biosynthesis inhibitor, phenidone insert ignore into journalissuearticles values(104 µg larva-1);, immediately prior to intrahemocoelic injections of the fungus Beauveria bassiana insert ignore into journalissuearticles values(Bals.); Vuill. insert ignore into journalissuearticles values(Deuteromycota: Hyphomycetes); insert ignore into journalissuearticles values(isolate No: HRI-215: 10 µg larva-1 from 2 x 106 blastospores ml-1);, sharply reduced insert ignore into journalissuearticles values(about 75 %); the nodulation reaction to the fungal challenges. Separate treatments with specific inhibitors of the major enzymes involved in eicosanoid biosynthesis, including phospholipase A2 insert ignore into journalissuearticles values(PLA2);, cyclooxygenase, and lipoxygenase, reduced nodulation reactions to fungal infections. These findings support the view that nodule formation is a complex process involving lipoxygenase and cyclooxygenase products. The inhibitory influence of phenidone, the dual cyclooxygenase and lipoxygenase inhibitor, was apparent within each time. Phenidone-treated larvae formed about 14 nodules/insect at 0.5 h post injection insert ignore into journalissuearticles values(hpi);, which increased to 54 at 8 hpi, whereas the ethanol-treated control larvae produced significantly more nodules at each time, from 49 nodules at 0.5 hpi to 147 at 8 hpi. The inhibitory effect of dexamethasone on nodulation was reversed by treating fungus-injected insects with the eicosanoid-precursor polyunsaturated fatty acid, arachidonic acid. These findings support our hypothesis that eicosanoids mediate insect cellular immune reactions to fungal infections in L. decemlineata.
Keywords : Nodulation, eicosanoid, B bassiana, L decmlineata, blastospore