Insect Science最新文献

The vast majority of all global species have circadian rhythm cycles that allow them to adapt to natural environments. These regular rhythms are regulated by core clock genes and recent studies have also implicated roles for microRNAs in this regulation. Oviposition is an important circadian behavior in the reproductive cycle of insect vectors of diseases, and little is known about the rhythm or its regulation in mosquitoes. Aedes albopictus is a diurnal mosquito that transmits arboviruses and is the major cause of outbreaks of dengue fever in China. We analyzed the oviposition rhythm patterns of A. albopictus under different light/dark conditions and show that the mosquitoes have an oviposition peak between zeitgeber time 9 (ZT 9) and ZT 12. Furthermore, the antagomir-mediated knockdown of expression of the microRNA miR-2940-1 affected the oviposition rhythm of A. albopictus. These data support the conclusion that miR-2940-1 is involved in the regulation of oviposition rhythm in A. albopictus and provide a foundation for using oviposition rhythms as a new target for vector mosquito control.

Given the limited availability of resources in nature, sexual attractiveness may trade off with immunocompetence, as the immunocompetence handicap hypothesis (ICHH) posits. In invertebrates, a direct link between trade-offs through hormonal/molecular effectors in sexual signals and immunity has not been found so far. Here, we assessed how variation in sexual signals affected parasite infection in two sex pheromone selected lines of the moth Chloridea virescens: an attractive line with a low ratio of 16:Ald/Z11-16:Ald and an unattractive line with a high ratio. When infecting these lines with an apicomplexan parasite, we found that the attractive Low line was significantly more susceptible to the parasite infection than the unattractive High line. Since the ratio difference between these two lines is determined by a delta-11-desturase, we hypothesized that this desaturase may have a dual role, i.e., in the quality of the sexual signal as well as an involvement in immune response, comparable to testosterone in vertebrates. However, when we used CRISPR/cas9 to knockout delta-11-desturase in the attractive Low line, we found that the pheromonal phenotype did change to that of the High line, but the infection susceptibility did not. Notably, when checking the genomic location of delta-11-desaturase in the C. virescens, we found that mucin is adjacent to delta-11-desaturase. When comparing the mucin sequences in both lines, we found four nonsynonymous SNPs in the coding sequence, as well as intronic variation between the two lines. These differences suggest that genetic hitchhiking may explain the variation in susceptibility to parasitic infection.

Continuous and long-term use of traditional and new pesticides can result in cross-resistance among pest populations in different fields. Study on the mechanism of cross-resistance and related genes will help resistance management and field pest control. In this study, the pesticide-resistance mechanism in Spodoptera frugiperda (FAW) was studied with field populations in 3 locations of South China. Field FAW populations were highly resistant to traditional insecticides, chlorpyrifos (organophosphate) and deltamethrin (pyrethroid), and had higher levels of cytochrome P450 activity than a non-resistant laboratory strain. Inhibition of P450 activity by piperonyl butoxide significantly increased the sensitivity of resistant FAW in 3 locations to chlorpyrifos, deltamethrin and chlorantraniliprole (amide), a new type of insecticide, suggesting that P450 detoxification is a critical factor for insecticide resistance in field FAW populations. Transcriptomic analysis indicated that 18 P450 genes were upregulated in the field FAW populations collected in 3 regions and in 2 consecutive years, with CYP321A8, the most significantly upregulated one. Knockdown of CYP321A8 messenger RNA by RNA interference resulted in an increased sensitivity to the 3 tested insecticides in the field FAW. Enzyme activity and molecular docking analyses indicated that CYP321A8 enzyme was able to metabolize the 3 tested insecticides and interact with 8 other types of insecticides, confirming that CYP321A8 is a key cross-resistance gene with a wide range of substrates in the field FAW populations across the different regions and can be used as a biomarker and target for management of FAW insecticide resistance in fields.

In agroecosystems, plants are constantly exposed to attack from diverse herbivorous insects and microbes, and infestation with one species may change the plant defense response to other species. In our investigation of the relationships among rice plants, the brown planthopper Nilaparvata lugens (Stål) and the rice blast fungus Magnaporthe oryzae, we observed a significant increase in the resistance of rice treated with rice blast to N. lugens, as evidenced by improved plant survival rates in a small population resistance study. Subsequent transcriptome data analysis revealed that the rice blast fungus can induce the expression of genes in the jasmonic acid (JA) and flavonoid pathways. Similar to the flavonoid pathway, the JA pathway also contains 2 types of genes that exhibit similar and opposite trends in response to N. lugens and rice blast. Among these genes, the osjaz1 mutant and the osmyc2 mutant were phenotypically confirmed to positively and negatively regulate rice resistance to N. lugens and rice blast, respectively. Subsequent mass spectrometry and quantification experiments showed that the exogenous application of methyl jasmonate (MeJA) can induce the accumulation of eriodictyol, naringenin and quercetin, as well as the expression of OsF3H, Os4CL5 and OsCHI in the flavonoid pathway. This suggests a close connection between the JA pathway and the flavonoid pathway. However, OsF3'H, which negatively regulates rice resistance to N. lugens and rice blast, did not show increased expression. Phenotypic and molecular experiments confirmed that OsMYC2 can bind to and inhibit the expression of OsF3'H, thus revealing the mechanism of rice resistance to N. lugens after treatment with rice blast. These findings will deepen our understanding of the interactions among rice, N. lugens and rice blast.

Distressed western carpenter ants, Camponotus modoc, produce alarm pheromone and substrate-borne vibrations. The alarm pheromone attracts nestmates but the effects of vibratory signals, or of bimodal pheromonal and vibratory signals, are not known. Worker ants of two Camponotus congeners reportedly stand still ("freeze") or run fast in response to engineered drumming vibrations inputted on plastic, but many responses to ant-produced vibratory signals on wood have not yet been investigated. Generally, orientating toward signalers under vertebrate predator attack seems maladaptive and not beneficial to ant colonies. We tested the hypotheses (1) that vibratory alarm signals cause freezing, rapid running but not attraction of nestmates, and (2) that bimodal alarm signals modulate responses to monomodal alarm signals, thereby possibly reducing predation risk. Laser Doppler vibrometry recordings revealed that the ants' vibratory signals readily propagate through ant nest lamellae, and thus quickly inform nest mates of perceived threats. With a speaker modified to record and deliver vibratory signals, we obtained drumming signals of distressed ants on a Douglas fir veneer, and bioassayed signal effects on ants in an arena with a suspended veneer floor. In response playback of vibratory signals, ants ran rapidly, or froze, but did not approach the vibratory signals. Exposed to alarm pheromone, ants frequently visited the pheromone source. However, concurrently exposed to both alarm pheromone and vibratory signals, ants visited the pheromone source less often but spent more time "frozen." The ants' modulated responses to bimodal signals seem adaptive but the reproductive fitness benefits are still to be quantified.

Hematophagous female mosquitoes are important vectors of numerous devastating human diseases, posing a major public health threat. Effective prevention and control of mosquito-borne diseases rely considerably on progress in understanding the molecular mechanisms of various life activities, and accordingly, the molecules that regulate the various life activities of mosquitoes are potential targets for implementing future vector control strategies. Many long non-coding RNAs (lncRNAs) have been identified in mosquitoes and significant progress has been made in determining their functions. Here, we present a comprehensive overview of the research advances on mosquito lncRNAs, including their molecular identification, function, and interaction with other non-coding RNAs, as well as their synergistic regulatory roles in mosquito life activities. We also highlight the potential roles of competitive endogenous RNAs in mosquito growth and development, as well as in insecticide resistance and virus-host interactions. Insights into the biological functions and mechanisms of lncRNAs in mosquito life activities, viral replication, pathogenesis, and transmission will contribute to the development of novel drugs and safe vaccines.

Wing dimorphism is regarded as an important phenotypic plasticity involved in the migration and reproduction of aphids. However, the signal transduction and regulatory mechanism of wing dimorphism in aphids are still unclear. Herein, the optimal environmental conditions were first explored for inducing winged offspring of green peach aphid, and the short photoperiod was the most important environmental cue to regulate wing dimorphism. Compared to 16 L:8 D photoperiod, the proportion of winged offspring increased to 90% under 8 L:16 D photoperiod. Subsequently, 5 differentially expressed microRNAs (miRNAs) in aphids treated with long and short photoperiods were identified using small RNA sequencing, and a novel miR-3040 was identified as a vital miRNA involved in photoperiod-mediated wing dimorphism. More specifically, the inhibition of miR-3040 expression could reduce the proportion of winged offspring induced by short photoperiod, whereas its activation increased the proportion of winged offspring under long photoperiod. Meanwhile, the expression level of miR-3040 in winged aphids was about 2.5 times that of wingless aphids, and the activation or inhibition of miR-3040 expression could cause wing deformity, revealing the dual-role regulator of miR-3040 in wing dimorphism and wing development. In summary, the current study identified the key environmental cue for wing dimorphism in green peach aphid, and the first to demonstrate the dual-role regulator of miR-3040 in photoperiod-mediated wing dimorphism and wing development.

In insects, melanism, a fundamental pigmentation process, is of significant importance in evolutionary biology due to its complex genetic foundation. We investigated the role of the RNA-binding gene Musashi (msi) in melanism in Laodelphax striatellus, a Hemiptera species. We identified a single L. striatellus msi homolog, Lsmsi, encoding a 357 amino acid protein with 2 RNA recognition motifs. RNA interference-mediated knockdown of LsMsi resulted in complete body melanism and increased cuticular permeability. Additionally, we found the involvement of G protein-coupled receptor A42 and tyrosine hydroxylase (Th) in L. striatellus melanism. Knockdown of LsTh lightened the epidermis, showing dehydration signs, while LsA42 knockdown enhanced LsTh expression, leading to melanism. Surprisingly, Lsmsi knockdown decreased both LsA42 and LsTh expression, which was expected to cause whitening but resulted in melanism. Further, we found that Lsmsi influenced downstream genes like phenoloxidase homolog LsPo and dopa decarboxylase (Ddc) homolog LsDdc in the tyrosine-mediated melanism pathway. Extending to Nilaparvata lugens and Sogatella furcifera, we demonstrated the conserved role of msi in melanism among Delphacidae. Given MSI proteins' roles in cancer and tumors in vertebrates, our study is the first to link msi in insects to Delphacidae body color melanization via the tyrosine-mediated pathway, offering fresh perspectives on the genetic basis of insect melanism and msi functions.

Disruption of the circadian clock can affect starvation resistance, but the molecular mechanism is still unclear. Here, we found that starvation resistance was significantly reduced in the core gene BmPer deficient mutant silkworms (Per^-/-), but the mutant's starvation resistance increased with larval age. Under natural physiological conditions, the weight of mutant 5th instar larvae was significantly increased compared to wild type, and the accumulation ability of triglycerides and glycogen in the fat bodies was upregulated. However, under starvation conditions, the weight consumption of mutant larvae was increased and cholesterol utilization was intensified. Transcriptome analysis showed that beta-oxidation was significantly upregulated under starvation conditions, fatty acid synthesis was inhibited, and the expression levels of genes related to mitochondrial function were significantly changed. Further investigations revealed that the redox balance, which is closely related to mitochondrial metabolism, was altered in the fat bodies, the antioxidant level was increased, and the pentose phosphate pathway, the source of reducing power in cells, was activated. Our findings suggest that one of the reasons for the increased energy burden observed in mutants is the need to maintain a more robust redox balance in metabolic tissues. This necessitates the diversion of more glucose into the pentose phosphate pathway to ensure an adequate supply of reducing power.

Behavioral division is essential for the sustainability and reproduction of honeybee populations. While accumulating evidence has documented that antibiotic exposure interferes with bee behavioral divisions, how the gut microbiome, host physiology, and genetic regulation are implicated in this process remains understudied. Here, by constructing single-cohort colonies, we validated that the gut microbiota varied in composition between age-matched nurse and forager bees. Perturbing the gut microbiota with a low dose of antibiotic retained the gut bacterial size, but the structure of the microbial community continuously diverged from the control group after antibiotic treatment. Fewer foragers were observed in the antibiotic groups in the field experiment. A combinatorial effect of decreased gut metabolic gene repertoires, reduced brain neurotransmitter titers, and downregulated brain immune genes could potentially be related to behavioral tasks transition delay. This work indicates that the disturbance to both the gut microbiome and host physiologies after antibiotic exposure may have implications on social behavior development, highlighting the need for further research focusing on antibiotic pollution threatening the honeybee population's health.