Effect Of Gradual And Double Increasing CO₂Concentrations On The Life History And Biochemical Substances In Multiple Generations Of Nilaparvata Lugens

Atmospheric carbon dioxide (CO2) levels continue to increase rapidly, mainly because of anthropogenic absurd activities, such as increased fossil fuel use and deforestation, resulting in global climate change. Elevated CO2alters the yield, quality and distribution of chemical substances of rice, which in turn may affect the growth and development, physiology and biochemistry of brown planthopper(Nilaparvata lugens) specifically feeding rice, as well as its other aspects. In this study, three CO2levels were used, which were ambient (CK) treatment with the CO2level by375ppm, gradual treatment with a increasing CO2level of25ppm per generation(CO2levels of375ppm in F1slowly rise to double level in F16), abrupt treatment with a double CO2level by750ppm. We had systematically examined the impacts of these three CO2treatments on the growth and reproduction of N. lugens in successive16generations, enzymes activities and gene expression levels of N. lugens nymph in four generations (F1, F6, F11, F16). The results were follow:1Effects of elevated CO2on the life table of N. lugensThe results showed that elevated CO2prolonged the nymph development times and shortened preoviposition period of N. lugens. Elevated CO2had no effect on the Female/Male and Macropterous/Brachypterous of N.lugens (P>0.05). However, significantly lower adult longevity, hatchability and fewer eggs and higher egg duration of N. lugens were observed in abrupt CO2treatment compared with gradual CO2treatment.2Effects of elevated CO2on the enzymes activities of N. lugensSignificantly lower ALP and sucrase and significantly higher activities of two protective enzymes (CAT and SOD), and two detoxifying enzymes (GST and CarE) and (AChE) were observed in the body of N. lugens in the abruptly increased CO2concentration treatment relative to ambient treatment (P<0.05). With the increase of generations, the activities of two digestive enzymes in abrupt treatment were significantly higher than the other two treatments. The differences of two protective enzymes in three treatments are not significant gradually, but the activities of two detoxifying enzymes and AChE apperared the trend by abrupt treatment<gradual treatment<ambient treatment. 3Effects of elevated CO2on expression levels of five relative genes of N.lugensWe tested the relative expression levels of five genes (EcR, JHE, Vg, hsp90and CYP6CS1) of N. lugens by qRT-PCR. The results showed that elevated CO2significantly decreased the relative expression levels of EcR and significantly reduced the expression quantities of JHE of N. lugens in Fi. The relative expression levels of Vg and hsp90was presented by abrupt treatment<ambient treatment<gradual treatment. Higher CYP6CS1gene expression was observed in F1, owing to the effects of elevated CO2. Then, the expression quantities of ambient treatment and gradual treatment are significantly higher than abrupt treatment in F6and F11, but few differences were observed among three treatments in F16.This study showed that elevated CO2had some effect on the individual life history, physiological metabolic enzymes activities, and molecular ecology of N. lugens. The results above indicated that the abrupt double atmospheric CO2concentration may be adverse to N. lugens, while gradual increasing CO2levels will promot the population development of N. Lugens. Results of this study partially elucidated the response characteristics and mechanism of N. Lugens to elevated CO2, and it’s significant to provide theoretical support and practical basis for the long-term population forecasts and control of N. Lugens under warming climate conditions.