The Effect ofBeauveria brongniartiiand its Secondary Metabolites on the Detoxification Enzymes of the Pine Caterpillar,Dendrolimus tabulaeformis

Abstract

The mortality of pine caterpillar, Dendrolimus tabulaeformis Tsai et Liu (Lepidoptera: Lasiocampidae), larvae treated with Beauveria brongniartii (Saccardo) Petch (Hypocreales: Clavicipitaceae) conidia and cell-free culture supernatants enriched for the secondary metabolites of the fungus was investigated. In addition, the effects of the treatments on the activities of two insect-related defense response proteins, glutathione S-transferase (GST) and esterase (EST), were measured over time. Bioassays were performed using a range of fungal spore (6 × 105 through 6 × 107 spores/mL) and supernatant extract concentrations (5.5–550 µg/mL). The results showed that the mortalities of D. tabulaeformis larvae were closely related to the concentration of the conidia and the metabolites of B. brongniartii. The differences among the treatments all reached a significant level. The activities of the two detoxifying enzymes, GST and EST, in the larvae increased simultaneously post-treatment. After infection with the conidial suspensions, the highest GST activity appeared at 3 days, and the activities of the caterpillars infected with 6 × 106 spores/mL and 6 × 107 spores/mL were significantly higher than in the control. Using α-naphthyl, the highest activity of EST also appeared at 3 days, and the differences for the three different concentrations were significant. A similar trend of change in the EST activity was observed using β-naphthyl. After treatment with the secondary metabolite solution, the highest GST activity appeared at 6 hr, and significant differences were found both for the different durations (2, 4, 6, 12, 24, and 48 hr) and in the three concentration groups. When using α-naphthyl, the EST activity peak appeared at 24 hr, and the differences were significant among the durations of 2, 4, 6, 12, 24, and 48 hr. The effect of the concentration of the secondary metabolite solution notably induced the EST activity in the insects, and a similar result was obtained using β-naphthyl. The data suggest that B. brongniartii produces secondary metabolites that disable the immune mechanisms of D. tabulaeformis, allowing the fungus to overcome and then kill its host. It was concluded that both the conidial suspensions and the metabolites of B. brongniartii were toxic to D. tabulaeformis larvae.

Effect of sublethal concentration of beauveria bassiana fungus on demographic and some biochemical parameters of predatory bug, Andrallus spinidens fabricius (Hemiptera: pentatomidae) in laboratory conditions

“…Fungal infection of insect increases glutathione S-transferase activity (15). Similar results were reported by Fan et al (36) conidia ml −1 . Induction of GST activity is an indication of a detoxification process (37).…”

Isolation and identification of fungal growth on Tribolium castaneum in stored wheat flour

“…The fungus frequently emerges from the insect's body to produce spores that, when spread by contact with other insects, can spread infection (Moino et al, 2002). Another explanation is the fungi secondary metabolites that increase the chance of insect death (Fan et al, 2013). The previously mentioned fungi have the ability to decompose cuticle layer to be able to penetrate the insect body and colonize it leading to death of these insects.…”

Dual application of entomopathogenic nematodes and fungi on immune and antioxidant enzymes of the greater wax moth, Galleria mellonella L.

“…Moreover, a joint application could easily overcome the host detoxification-related enzymes such as esterase and glutathione S-transferase (Fan et al 2013). Esterase (EST) is an important detoxifying enzyme in vivo, which hydrolyzes the esteric bond in synthetic chemicals.…”