摘要: 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 theHoxgeneUltrabithorax(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 thatUbxmay be amir-9atarget, and used dual luciferase reporter assays and injected micro RNA (miRNA) mimics and inhibitors to confirm the interactions betweenmir-9aandNlUbx. We measured themir-9aandNlUbxexpression 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, andNlUbxthat regulate wing length in BPHs. When host quality was low,NlInR1expression in the nymph terga increased andNlInR2expression decreased; this led to a highermir-9alevel, which in turn reduced theNlUbxtranscript 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 controlUbxexpression in BPH forewings.

摘要: The predatory bug,Orius majusculus(Reuter), is an important predator of thrips commercially produced for augmentative releases using the eggs of the Mediterranean flour mothEphestia kuehniella(Zeller). In this study, we assessed the potential for using frozen adults of fruit flies,Drosophila melanogaster(Meigen), either as nymphal rearing diet or as diet throughout the entire life-cycle. We compared life-history traits and reproduction of predators when fedD. melanogasterwith high lipid body content (lipid-rich) and with high protein body content (protein-rich), using a diet of 100%E. kuehniellaeggs as control. We also analyzed the biochemical composition of both prey and predator in order to assess the nutritional quality of each diet, which partially explained the adequacy of the different diets forO. majusculus. There were significant differences between predators fed the two types ofD. melanogaster, with the protein-rich flies as diet providing the best results in terms of mortality and fecundity. Furthermore, we show that while feedingO. majusculusthroughout their development withD. melanogasterincreases mortality and reduces reproduction, protein-richD. melanogastercan be used as nymphal diet with minimal reduction in reproductivity and minimal increase in mortality.

摘要: The geomagnetic field (GMF) is well documented for its essential role as a cue used in animal orientation or navigation. Recent evidence indicates that the absence of GMF (mimicked by the near-zero magnetic field, NZMF) can trigger stress-like responses such as reduced body weight, as we have previously shown in the brown planthopper,Nilaparvata lugens. In this study, we found that consistent with the significantly decreased body weight of newly emerged female (-14.67%) and male (-13.17%) adultN. lugens, the duration of the phloem ingestion feeding waveform was significantly reduced by 32.02% in 5th instar nymphs reared under the NZMF versus GMF. Interestingly, 5th instar nymphs that exhibited reduced feeding had significantly higher glucose levels (+16.98% and +20.05%; 24 h and 48 h after molting), which are associated with food aversion, and expression patterns of their appetite-related neuropeptide genes (neuropeptide F, down-regulated overall;short neuropeptide F, down-regulated overall;adipokinetic hormone, up-regulated overall; andadipokinetic hormone receptor, down-regulated overall) were also altered under the absence of GMF in a manner consistent with diminishing appetite. Moreover, the expressions of the potential magnetosensorcryptochromes (Crys)were found significantly altered under the absence of GMF, indicating the likely upstream signaling of the Cry-mediated magnetoreception mechanisms. These findings support the hypothesis that strong changes in GMF intensity can reduce adult body weight through affecting insect feeding behavior and underlying regulatory processes including appetite regulation. Our results highlight that GMF could be necessary for the maintenance of energy homeostasis in insects.

摘要: Nutrition contributes to honey bee caste differentiation, but the role of individual nutrients is still unclear. Most essential amino acid contents, except that of methionine (Met), are greater in royal jelly than worker jelly. After similar to 3.5 d, the Met content in the latter was slightly greater than in the former. Met is the major raw material used in the synthesis of S-adenosyl-L-methionine, an active methyl donor for DNA methylation, which is an epigenetic driver of caste differentiation. Here, we tested whether Met regulates caste differentiation in honey bees by determining its effects on the caste development of bees receiving four diets: the basic, basic + 0.2% Met, basic + 0.2% Met + 20 mg/kg 5-azacytidine, and basic + 20 mg/kg 5-azacytidine. The presence of Met decreased the adult bee body length and the numbers of ovarioles, indicating that Met may direct the development of female larvae toward worker bees. The upregulated expression ofSAMS,Dnmt1, andDnmt3caused by Met exposure in 4-d-old larvae indicated that the worker-inductive effects of Met may occur through the promotion of DNA methylation. We investigated the co-effects of Met and glucose on bee development, and found that the effects of an increased glucose level on the number of ovarioles and body length did not strengthen the worker-inductive effects caused by Met. Our results contribute to caste development theory and suggest that Met-as a methyl donor-plays a regulatory, but not decisive, role in caste differentiation.

摘要: Chitin deacetylases (CDAs, including CDA1 and CDA2) are considered key enzymes for body cuticle formation and tracheal morphogenesis in various insect species. However, their functions in the formation of the cuticular intima of the foregut and hindgut are unclear. Here, we investigated the roles of their respective genes LmCDA1 and LmCDA2 in this process, in the hemimetabolous insect Locusta migratoria. Transcripts of LmCDA1 and LmCDA2 were highly expressed both before and after molting in the foregut. In the hindgut, their expression was high only before molting. In both the foregut and hindgut, LmCDA1 protein was localized in the basal half of the chitin matrix (procuticle), whereas LmCDA2 was detected in the upper half of the procuticle. Knockdown of LmCDA1 by RNA interference (RNAi) in 5th-instar nymphs caused no visible defects of the hindgut cuticle. By contrast, the chitinous lamellae of the cuticular intima in the foregut of knockdown animals were less compact than in control animals. RNAi against LmCDA2 led to thickening of both the foregut and hindgut cuticles, with a greater number of thinner laminae than in the respective control cuticles. Taken together, our results show that LmCDA1 and LmCDA2 have distinct, but overlapping, functions in chitin organization in the foregut cuticle. However, in the hindgut, this process seems independent of LmCDA1 activity but requires LmCDA2 function. Thus, the CDAs reflect tissue-specific differences in cuticular organization and function, which need further detailed molecular and histological analyses for full comprehension.