Effects of elevated CO2 treatment of Populus davidiana × P. bolleana on growth and detoxifying enzymes in gypsy moth, Lymantria dispar

To date, elevated CO₂ concentrations in the environment caused by various human activities influence diverse areas of life, including the interactions between insects and plants. The Lymantria dispar is one of the most severely destructive pests, which further could inflict ecological and economical damage. In this experiment, one-year-old Populus davidiana × P. bolleana plants were grown in CO₂-enhanced environments for one month at three different CO₂ concentrations: 397 ppm (atmospheric CO₂ concentration), 550 ppm and 750 ppm (two predicted elevated CO₂ concentrations). The 3rd instar L. dispar larvae then fed on the treated poplar seedlings covered in a nylon bag. The L. dispar larvae fed on poplar seedling treated for 96 h showed the highest growth rate at all CO₂ concentrations. Enzymatic activity of treated larvae showed the highest GST and P450 activity at 750 ppm CO₂. The relative expressions of seven CYP and ten GST genes in L. dispar larvae were analyzed quantitatively using real-time RT-PCR, which the results were expressed variably. Compared to 397 ppm CO₂, the expression of CYP4L23 was down-regulated, while the expressions of other CYP genes were up-regulated. Meanwhile, only GSTo1 gene showed down-regulated at 48 h and 96 h in 750 ppm CO₂ treatment, while GST expression level for the other nine GST genes showed up-regulated at 48 h and 72 h. These results offer the insight into plant-insect interactions under global climate change and furthermore will provide essential information for strategic pest control based on biochemical and molecular levels changes in gypsy moths.