Plants accumulate phenolic compounds such as tannic acid to resist insect herbivores. The survival of insects exposed to toxic secondary metabolites depends on the detoxification metabolism mediated by limited groups of glutathione S-transferases (GSTs). Micromelalopha troglodyta (Graeser) (Lepidoptera: Notodontidae) is an important foliar pest of poplar trees. GSTs play an important role in xenobiotic detoxification in M. troglodyta. Five GST genes were identified in M. troglodyta and were classified into five different cytosolic GST classes, delta, omega, sigma, theta, and zeta. Real-time fluorescent quantitative polymerase chain reaction (qPCR) was used to determine the mRNA expression of the five cloned GSTs in the midguts and fat bodies of M. troglodyta. The mRNA expression of the five GSTs was significantly induced when M. troglodyta was exposed to tannic acid. To further understand the tannic acid regulatory cascade, the 5′-flanking promoter sequences of the five MtGSTs were isolated by genome walking methods, and the promoters were very active and induced by tannic acid. In summary, the induction of GST mRNA expression was due to the response of five MtGST promoters to tannic acid. Therefore, MtGST promoters play an important role in the regulation of GST transcription.
The subterranean termite Reticulitermes chinensis Snyder is an important pest in China. We determined the inhibition of six selected insecticides to acetylcholinesterase (AChE) extracted from R. chinensis. Our results yielded half maximal inhibitory concentrations (I50) for each of the insecticides to be 3.49 × 10–3 M for methomyl, 3.87 × 10–2 M for phoxim, 2.18 × 10–3 M for triazophos, 1.89 × 10–3 M for profenosos, 1.10 × 10–3 M for malathion, and 4.39 × 10–2 M for omethoate. Furthermore, the inhibitory activity of AChE by the six insecticides was increased with the increase of insecticide concentration from 3.3 × 10–7 to 5 × 10–3 M. These results provide a theoretical basis for the management of R. chinensis.
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