Effects of Elevated CO2 on the Fitness of Three Successive Generations of Lipaphis erysimi.

To assess the effect of elevated CO2 on the development, fecundity, and population dynamic parameters of L. erysimi, the age-stage, two-sex life table was used to predict the individual fitness and population parameters of three successive generations of L. erysimi in this study. The results show that a significantly longer total pre-adult stage before oviposition (TPOP) was observed in the third generation compared with the first generation of L. erysimi under the 800 µL/L CO2 treatment. The fecundity is significantly lower in the 800 µL/L CO2 treatment than that in the 400 µL/L CO2 treatment in the third generation of L. erysimi, which indicates that elevated CO2 had a negative effect on the individual fitness parameters of L. erysimi. Additionally, the life expectancy (exj) is significantly lower under the 800 µL/L CO2 treatment than that under the 400 µL/L CO2 treatment in the three successive generations. A significantly higher intrinsic rate of increase (r) and finite rate of increase (λ) were found in the second generation compared with those in the first and third generations of L. erysimi under the 800 µL/L CO2 treatment. Moreover, significantly lower r and λ were observed under the 800 µL/L CO2 treatment compared with those under the 400 µL/L and 600 µL/L CO2 treatments in the first generation of L. erysimi, which indicates that elevated CO2 has a short-term effect on the population parameters (r and λ) of L. erysimi. Our experiment can provide the data for the comprehensive prevention and control of L. erysimi in the future with increasing CO2 levels.

An InR/mir-9a/NlUbx regulatory cascade regulates wing diphenism in brown planthoppers.

Wing polymorphism significantly contributes to the ecological success of some insect species. For example, the brown planthopper (BPH) Nilaparvata lugens, which is one of the most destructive rice pests in Asia, can develop into either highly mobile long-winged or highly fecund short-winged adult morphs. A recent study reported a highly provocative result that the Hox gene Ultrabithorax (Ubx) is expressed in BPH forewings and showed that this wing development gene is differentially expressed in nymphs that develop into long-winged versus short-winged morphs. Here, we found that Ubx may be a mir-9a target, and used dual luciferase reporter assays and injected micro RNA (miRNA) mimics and inhibitors to confirm the interactions between mir-9a and NlUbx. We measured the mir-9a and NlUbx expression profiles in nymphs and found that the expression of these two biomolecules was negatively correlated. By rearing BPH nymphs on host rice plants with different nutritional status, we were able to characterize a regulatory cascade between insulin receptor genes, mir-9a, and NlUbx that regulate wing length in BPHs. When host quality was low, NlInR1 expression in the nymph terga increased and NlInR2 expression decreased; this led to a higher mir-9a level, which in turn reduced the NlUbx transcript level and ultimately resulted in longer wing lengths. Beyond extending our understanding of the interplay between host plant status and genetic events that modulate polymorphism, we demonstrated both the upstream signal and miRNA-based regulatory mechanism that control Ubx expression in BPH forewings.

Time-dependent stress evidence in dynamic allocation of physiological metabolism of Nilaparvata lugens in response to elevated CO2.

To assess the time-dependent stress evidence in dynamic allocation of physiological metabolism of Nilaparvata lugens nymphs in response to elevated CO2, we measured the time-dependent allocation of nutrient compositions and physiological metabolism in the bodies of N. lugens at 1h, 4h and 12h under elevated CO2. Elevated CO2 significantly increased the contents of nutrient compositions (protein, glucose and total amino acids) and catalase (CAT) enzyme activity in the body of N. lugens at 12h relative to 1h and 4h (P < 0.05). Significantly higher genes expression levels of acetylcholinesterase (AChE), heat shock protein (HSP70) and vitellogenin gene (vg) were observed in the body of N. lugens compared with those in ambient CO2 at 4h (P < 0.05). These results showed that there was an instantaneous reaction of N. lugens nymphs to elevated CO2, which indicated N. lugens may enhance stress defense response to future increasing CO2 levels.