Effects of Zinc on CarE Activities and Its Gene Transcript Level in the English Grain Aphid, Sitobion avenae

As a selective stress, heavy metals play an important role in inducing the adaptive adjustments of insects to changing environments. Carboxylesterase (CarE) is one kind of biomarker that could help us to explore the adaptation mechanism of aphids to heavy metal stress. In this study, CarE activity and gene expression level were investigated in English grain aphids, Sitobion avenae (F.) (Hemiptera: Aphididae), exposed to Zn2+ at concentrations of 0, 400, and 1600 mg/kg for 5, 15, 25, and 30 generations. The results showed that the CarE activity was significantly different between different Zn2+ concentrations and different generations. The CarE activity significantly decreased with increasing generations. In the higher generations, the CarE activity was strongly inhibited by the 1600 mg/kg of Zn2+. Realtime quantitative PCR revealed that the CarE gene expression pattern in S. avenae was up-regulated under the condition of 400 mg/kg and 1600 mg/kg of Zn2+, but a significant difference was not found after long-term exposure to high concentrations of Zn2+. It was concluded that CarE could be the sensitive biomarker for S. avenae response to the presence of Zn2+. In order to adapt to heavy metal Zn2+ stress, S. avenae had particular patterns of gene expression under long-term stress.