Insect Science最新文献

The ovary plays a crucial role in the female reproductive system of insects and is vital for the perpetuation of insect populations. The insulin/insulin-like growth factor signaling (IIS) and target of rapamycin (TOR) signaling network play a key role in controlling ovarian development and maturation during the adult stage. However, the pupal stage is a critical developmental phase in the reproductive system of holometabolous insects, and the regulatory role of the IIS/TOR network during this stage remains to be elucidated. In this study, we observed that during the pupal stage, the enlargement of ovarian development was accompanied by a corresponding increase in messenger RNA expression levels of genes within the IIS/TOR signaling pathway and insulin levels in the hemolymph. Decapitation experiments, serving as a pivotal approach to assess the regulatory role of the IIS signaling pathway in ovarian development, demonstrated that decapitation markedly inhibited ovarian development at this critical stage. Exogenous insulin administration significantly increased the phosphorylation levels of FOXO, S6K, and 4E-BP, thereby enhancing ovarian development and resulting in significant elongation of the ovarioles. In contrast, the injection of IIS/TOR pathway inhibitors, LY294002 and Rapamycin, reduced the phosphorylation of these proteins, inhibiting ovarian development during the pupal stage and leading to a significant shortening of the ovarioles, negatively impacting the reproductive performance of adult females. The current findings indicate that the IIS/TOR signaling network significantly regulates ovarian development during the pupal stage of Spodoptera frugiperda, providing new molecular insights for the development of pest management strategies.

Silkworm is a typical monophagous insect that can only feed on fresh mulberry leaves. The mechanism for this monophagous nature is not fully understood. One bitter gustatory receptor (GR) GR66 located on the maxilla of the mouthpart has been reported to be an important factor influencing the feeding preference of silkworm. However, the preference of GR66 mutants for a nonhost plant was very low, suggesting that other factors related to silkworm monophagy need to be further explored. In this study, 10 bitter GRs were screened out based on their specific high expression in the maxilla of silkworm, and the 4 most expressed GRs (GR15, GR43, GR69, and GR66) were knocked out by clustered regularly interspaced short palindromic repeats (CRISPR) / CRISPR-associated nuclease 9. Feeding experiments showed that except for GR69^-/-, the host range of GR43^-/-, GR15^-/-, and GR66^-/- expanded remarkably, and both GR43^-/- and GR66^-/- revealed the highest preference for the nonhost plants. Moreover, the strict preference for mulberry leaves was almost eliminated in the double mutant silkworms of GR43^-/- and GR66^-/-. These results imply that it is likely that a variety of different bitter GRs are involved in determining the monophagy of silkworm larvae. In addition, GR15 mutation significantly inhibited ovarian development, resulting in a significant decrease in oviposition. These findings enhance our understanding of the monophagous nature of silkworms and provide a possibility for the molecular breeding of polyphagous silkworms in the future.

How phenotype varies across geographic space constitutes a key question in current evolutionary biology. Species with widespread geographic ranges are helpful models for examining phenotype variation patterns. Here we examined body size and tegmen shape variation in 12 populations of widespread agricultural pest Dichroplus elongatus collected in Central-West Argentina. D. elongatus showed significant phenotypic variation. Combining linear and geometric morphometric techniques reveals differences in body size and tegmen shape between sexes. General linear mixed models (GLMMs) analyses showed that body size is mainly associated with variables related to temperature of the warmest trimester and temperature annual range along a latitudinal gradient. Individuals achieve larger body sizes at colder areas with lower thermal amplitude. The GLMMs procedures to test allometries demonstrated that most of the analyzed traits scaled isometrically in both sexes indicating that the shape of the individual will not modify with changes in body size. Thorax length is the only trait that scaled hypoallometrically although there were sex-specific differences. Climatic conditions, mainly temperature and precipitations, molded isometric and allometric trait patterns. The detected clinal patterns of phenotypic variation of D. elongatus from Central-West Argentina is likely to be the result of local adaptation to temperature and phenotype plasticity along climatic gradients, and identify geographic areas in where this species showed bigger body size and would undergo greater dispersal capacity. Finally, our results offer insights into how environmental changes may impact the species dispersal and adaptability, advising targeted control and management strategies for this agricultural pest.

Insects can effortlessly walk on various substrate surfaces using attachment pads on their feet, even upside down on smooth surfaces. These pads undergo frequent deformation throughout the lifecycle of insects to achieve stable adhesion. Interest in insect adhesion spans 100s of years; studies have indicated the special mechanical properties and intricate structural design of insect attachment pads. However, the genetic basis of their function remains unclear. Resilin, an elastic protein widely distributed in insect exoskeletons, plays a crucial role in many physiological activities. Here, we identified a resilin-like protein in the Lepidopteran insect Bombyx mori and generated mutants for this gene. The resulting adults exhibited "slipping" phenotype and reduced attachment ability. Further behavioral investigations, microscopic observations and mechanical performance tests, confirmed that the mutation stiffened the attachment pads, reducing flexibility and effective contact area, which ultimately led to decreased adhesive ability in adults. Molecular-level analyses revealed that the resilin-like mutation led to differential expression of melanin metabolism-related genes, potentially explaining the hardening and abnormal pigmentation of the attachment pads. Our results provide genetic and phenotypic evidence demonstrating the significant role of resilin in insect attachment.

Leptinotarsa decemlineata (Say) (Colorado potato beetle, CPB) is a notorious pest of potatoes. Its hardened forewings, known as elytra, protect the hindwings and the abdomen against enemies and chemical pesticides. Ubx plays a crucial role in differentiating insect wings, but the molecular mechanism remains unclear. Our research showed that Ubx is highly expressed in the T3 thoracic segment (T3) and appendages, while Ubx is absent in the forewings. RNA interference for Ubx resulted in the dorsal plate of the T3 being shifted toward the T2, hindwings were sheathed from the membranous in adults, and forewings were curling. The hindwing development-related genes downstream of Ubx, including LdDpp, LdIro, LdVg, LdWg, and LdASH, were significantly up-regulated in Ubx-inhibited insects compared with the control, by 2.40, 1.88, 1.81, 1.89, and 2.81 times, respectively. After feeding 20-hydrosyecdysone (20E), the forewing was flatter and more stretched than the control, leading to increased wing area, which indicates Ubx regulation is associated with the feedback of ecdysteroids. The expression levels of 3 ecdysteroid receptor genes EcR, EcRA, and EcRB were significantly lower in knocking down LdUbx insects than the control and was able to be recovered by 20E feeding, suggesting that ecdysteroid is associated with LdUbx-regulated wing development. Cosilencing LdUbx and LdAkt genes significantly inhibited the growth of forewings and hindwings, reducing the area of the wings. Together, our findings suggested that LdUbx regulates wing development along with ecdysteroid and insulin-like peptide signaling pathways, which provides a novel molecular mechanism of wing development and differentiation in insects.

Obligate endosymbionts of sap-sucking auchenorrhynchan insects of Hemiptera colonize the bacteriomes and are transmitted vertically through the ovaries to the offspring of host insects, but the critical time of symbiont transmission and molecular mechanisms underlying the process remain unknown. We used histological and transmission electron microscopy, 16S rDNA amplification sequencing and transcriptome analyses to explore the vertical transmission of bacteriome-associated symbionts in the cicada Hyalessa maculaticollis. We find that the symbiont Candidatus Karelsulcia muelleri (hereafter Karelsulcia) proliferates and changes shape after the adult cicadas emerged for 3 h, which is then extruded to the hemolymph from the basal membrane of bacteriome units. The yeast-like fungal symbiont (YLS) harbored in bacteriome sheath cells is released freely along with Karelsulcia. As ovaries mature, Karelsulcia and YLS infect oocytes of cicadas that had emerged for 60 h, and begin to gather at the posterior pole of oocytes, where they form a symbiont ball in each oocyte. Expressions of genes associated with cytoskeletal organization, endocytosis, amino acid transporter and lipid synthesis increase in the newly emerged adults, mediating the transport of substances during the transmission of symbionts. The amino acid-sensitive mechanistic target of the rapamycin pathway is one of the crucial pathways coordinating the vesicle-mediated symbiotic transmission. The insulin signaling pathway potentially together with insect hormones synergically regulate insect fertility and affect yolk deposition, which is closely related to the symbiont infection of ovaries. This study highlights the importance of signaling pathways in regulating the vertical transmission of symbionts in sap-feeding auchenorrhynchan insects.

Nutritional ecology examines the environmental effects on nutritional needs, food intake and foraging behaviors, and the use of nutrients ingested by animals. Adults of many insects' species feed on nectars rich in sugars allowing them to match the nutritional needs necessary for reproduction. Among insects, Lepidoptera are often considered opportunistic foragers that visit a wide variety of available flowers, although with some preferences. While nutritional ecology of diurnal Lepidoptera is beginning to be explored, very little work focuses on nocturnal species because they are complicated to study in the wild. To address this, we used new laboratory approaches to study feeding behaviors (number and duration of visits to artificial flowers, food preferences associated with the texture and odors of the flowers) as well as gustatory detection by antennae (proboscis extension reflex) in the male crop pest moth Agrotis ipsilon. We showed that (i) food responsiveness is age-dependent and increases mainly with sugar quantity and marginally with sugar quality, (ii) diet quality impacts feeding behaviors in the first days of adulthood, and (iii) male moths choose their food through floral cues. Taken together, these data allow to define this species as a generalist forager with a preference for flowers with sugary nectars rich in sucrose, fructose, and glucose. Our results thus provide considerable information on the close links between food sources and nutritional ecology in this species, which is important for guiding future studies on their behavioral ecology, population dynamics, as well as for population monitoring and for regional pest management.

The brown planthopper (BPH), Nilaparvata lugens (Stål), is the most important rice pest in China and other East Asian countries. Identifying their source areas and predicting their population dynamics are crucial for managing migratory pests. Northern South China (NSC) is one of the key regions for northward BPH migration and a direct source of BPH in the key rice-growing area of the Lower Yangtze River Valley (LYRV). Hence, this study aimed to explore the environmental drivers affecting the population dynamics of BPH in NSC, and develop models for predicting the immigration levels in the LYRV. Initially, the BPH immigrants in NSC were identified to have mostly originated from northern and north-central Vietnam, Laos, and northeastern Thailand (15°-22° N) in May by using a trajectory analysis approach. The population model showed that immigration size of BPH in NSC in May can be predicted by the temperature observed in February over these source areas combined with the probability of BPH from south-central Vietnam (their principal overwintering region) immigrating to these source areas in March. Subsequently, the immigration size of BPH in NSC in May combined with the onset time of the South China Sea Summer Monsoon (a sign of rain belt movement and arrival of the flood season in China), can be used to predict the immigration level of BPH in the LYRV in July. These 2 prediction models could forecast nearly 2 months in advance, allowing time for effective control measures to be implemented.

The seasonality of Haemaphysalis longicornis in the United States comprises overlapping life stages in the spring and summer. This is partially attributed to the ability of all stages to survive the winter. Physiological condition in ticks refers to nutritional reserve levels and is often used to characterize tick populations. To determine if lipids were suitable for estimating the physiological condition in H. longicornis, lipid content was measured in unfed laboratory-reared ticks for up to 480 d. The results showed that lipids decrease significantly over time in adults (36% at 183 d), nymphs (33% at 63 d) and larvae (28% at 102 d) and could be used to study the population structure of field-collected H. longicornis. Lipids extracted from field-collected ticks (March to October) were measured to determine if different groups or cohorts could be identified during the season. The spring nymph population included high- and low-lipid groups that partially overlapped in April and May. In larvae, the lipid content of ticks in the spring was significantly higher than in the fall, suggesting that active larvae in the early fall do not overwinter. The analysis of lipids in adults showed that high- and low-lipid adults were present throughout the season, suggesting a continuous influx of recently molted adults until the end of the adult season, where only low-lipid ticks are found. The analysis of physiological condition in the Asian longhorned tick demonstrated a complex univoltine structure with some overlap in adults from different years.