Insect Science最新文献

Ceratitis capitata (Wiedemann) is a cosmopolitan pest of economic importance. It is controlled by using the Sterile Insect Technique (SIT), which involves rearing and release of sterile males destined to mate with wild females, causing generation-to-generation suppression. Medflies are colonized by microorganisms, primarily the Enterobacteriaceae, with the genera Klebsiella and Enterobacter being the most common. Such microbiota contributes to host fitness. During the SIT, diet with antibiotics and irradiation for sterility of adults alter microbiota. We aimed to determine the role of Medfly microbiota on resistance to abiotic stress conditions, evaluating its function under: (i) starvation, (ii) elevated temperatures, and (iii) dry environments. These conditions simulate challenges Medfly may encounter after release, which differ from controlled rearing environments. We compared adult survival between symbiotic and aposymbiotic individuals, under starvation, two thermal regimes (25 and 30 °C) or two humidity regimes (20%-25% and 80%-90% R.H.). Aposymbiotic individuals were obtained after providing them with water containing a mixture of antibiotics and methylparaben. Treatment with antimicrobials effectively reduced the gut microbiota. While starvation had no significant effect on survival, a higher proportion of aposymbiotic individuals died earlier at 30 °C and under dry humidity, with the effect being more pronounced after 48 h. Our results suggest that microbiota plays a role in adaptation of Medfly under environmental stress. We report for the presence of a culturable yeast in the digestive tract of C. capitata, Zygosaccharomyces rouxii. Providing a probiotic adult diet with bacteria and Z. rouxii prior to release could improve SIT outcomes under adverse conditions.

American foulbrood (AFB) disease, caused by the bacterium Paenibacillus larvae, is a devastating disease affecting honeybee (Apis mellifera L.) populations worldwide. Commonly treated with antibiotics, which have negative impacts on both honeybees and the environment, there is an urgent need for alternatives in AFB control. This study aimed to investigate the effects of gallic acid (GA) on honeybee larvae challenged with P. larvae spores and explore its modulation of larval microbiota. Our results demonstrated that in the presence of P. larvae spores, coadministration of 125 µg/mL GA significantly increased the survival rate and body weight of honeybee larvae. Molecular docking analyses revealed that GA competitively binds to spore germination proteins YndE and GerM, with affinities comparable to L-tyrosine and stronger than uric acid, respectively, suggesting interference with P. larvae spore germination. 16S rRNA gene amplicon sequencing revealed that GA treatment augmented bacterial diversity and enriched lactic acid bacteria (LAB) in honeybee larvae. Whole-genome sequencing of 2 LAB strains, Apilactobacillus kunkeei GL-2 and Enterococcus faecium GL-6, isolated from GA-treated larvae, unveiled their potential to produce antimicrobial secondary metabolites and bacteriocins, which may contribute to their competitive advantages against P. larvae. Notably, the E. faecium GL-6 strain possessed genes encoding gallate decarboxylase, enabling GA utilization, and 2 putative bacteriocinogenic genetic clusters for enterolysin A and enterocin L50 a/b. These findings suggest that GA and the GL-6 strain hold potential as preventive measures against AFB disease in honeybees through modulation of gut microbiota and competitive inhibition of P. larvae.

Anastrepha fraterculus is a significant fruit fly pest in Argentina and other South American countries. Previous studies showed the key role of gut bacteria in the protection and nutrient assimilation of fruit flies, particularly the importance of the biological fixation of nitrogen (diazotrophy). The presence of diazotrophic bacteria in A. fraterculus sp. 1 has been demonstrated through molecular, culture-independent methods. This study is aimed to characterize the composition and diversity of culturable gut bacteria of A. fraterculus sp. 1 males from different origins, and explore their metabolic roles, focusing on diazotrophic bacteria. Three male groups were studied: wild-caught (WW), lab-reared from wild larvae (WL), and lab-colony raised (LL). Gut bacteria were collected and characterized via 16S rRNA gene sequencing, with potential diazotrophs screened using selective media (SIL and NFb). Phylogenetic analysis of 16S rRNA gene mapped potential diazotrophs across the bacterial collection, while biochemical profiling and ARDRA (Amplified rDNA Restriction Analysis) were used to quickly differentiate diazotrophic bacteria. PCR testing for the nifH gene, associated with nitrogen fixation, was also performed. Bacterial diversity was highest in WW, followed by WL, and lowest in LL. In LL and WL, Enterobacter was the most frequent genus, while Klebsiella dominated in WW. Among the 20 SIL+ isolates identified, 10 came from WW, 9 from WL, and 1 from LL. One of these isolates (Enterobacter sp.) was tested as a supplement to the adult diet, without showing a beneficial effect on males pheromone calling behavior. Three isolates were also NFb+; two had the nifH gene. ARDRA was effective for rapid diazotroph discrimination. These findings highlight the potential of gut symbiotic bacteria in eco-friendly pest management strategies like the sterile insect technique (SIT). By using diazotrophic bacteria, protein requirements in artificial diets could be reduced, cutting costs and improving the affordability of SIT programs.

RNA N⁶-methyladenine (m⁶A) modification represents a pivotal epigenetic modification that facilitates the remodeling of gene expression and regulates a variety of biological processes via certain post-transcriptional mechanisms. However, the specific function of RNA m⁶A modification in insect male reproduction remains unclear. In this study, we explored the molecular mechanism by which METTL3/METTL14-mediated RNA m⁶A modification regulates male reproduction in the invasive pest Bactrocera dorsalis. The results showed that BdMettl3 and BdMettl14 were highly expressed in fat body (FB) and male accessory glands (MAGs). Knockout of BdMettl3 or BdMettl14 decreased the expression level of m⁶A in B. dorsalis, resulting in testicular deformities and a significant reduction of viable sperm number. Specifically, BdMettl3 or BdMettl14 knockout reduced the titer of 20-hydroxyecdysone (20E, the active form of ecdysone) in males. The messenger RNA (mRNA) of Disembodied, one of the 20E synthesis genes, was modified by m⁶A, and its expression increased the titer of 20E. The mRNA m⁶A level of Disembodied obviously decreased after the knockout of BdMettl3 or BdMettl14, suggesting that RNA m⁶A modification regulates testis development and fecundity by modulating 20E synthesis. Taken together, this study indicates that METTL3/METTL14-mediated RNA m⁶A modification presents a new regulatory mechanism for male reproduction in B. dorsalis, serving as a potential target for the control of B. dorsalis.

Genetic modification via gene editing has become a widely adopted and demonstrably effective method in functional gene research within entomology. However, the optimal efficiency and simplicity of delivering exogenous guide RNA-clustered regularly interspaced short palindromic repeats-associated protein 9 complexes into target tissues are crucial for successful gene editing. The Receptor-Mediated Ovary Transduction of Cargo (ReMOT) strategy, which simplifies the delivery process, target-site selection, technical requirements, and delivery cost compared with embryonic microinjection, enabling efficient editing at the germline level, is gaining increasing attention. Although the feasibility and advantages of this technique have been demonstrated in various insect species, further optimization of operational details and the overcoming of further bottlenecks are still required. This review focuses on advances in developing ReMOT as a valuable technology, exploring its applicability, rationale for selecting the ovary as a delivery target site, factors influencing its efficiency, and improvement recommendations. The versatility and effectiveness of ReMOT make it a promising method for researchers looking to make precise genetic modifications with greater ease and efficiency.

Insects represent one of the most evolutionarily successful groups, with their diversity hypothesized to be related to the regulatory roles of Hox genes, a set of related genes encoding homeodomain transcription factors determining the identity of segments along the anterior-posterior axis of the embryo. However, functional insights into the roles of Hox genes in primitive ametabolous insects, which represent the critical transition from aquatic crustaceans to winged insects, have been limited. In this study, we identified complete protein-coding sequences of 10 Hox genes in the Zygentoma Thermobia domestica, and applied clustered regularly interspaced short palindromic repeats (CRISPR) / CRISPR-associated nuclease 9 (Cas 9) mediated gene knockout (KO) to decipher their functions. We found that the roles of pb, Dfd, and Scr are vital in specifying the appendages of the head in T. domestica, and these roles are relatively conserved in crustaceans and winged insects. Antp is essential for the development of the prothorax segment and the first pair of legs in T. domestica. Ubx and abd-A fully repress appendage development in the abdomen of T. domestica, which implies a functional switch from crustaceans to insects. Additionally, the role of ftz in segmenting the abdomen of T. domestica suggests it has acquired new functions in primitive insects, beyond its traditional Hox-like roles. Although KOs of lab, Hox3, and Abd-B did not result in obvious external phenotypic changes, they led to a significant decrease in hatching rates and substantial deviations in daily survival numbers compared to the negative control. These findings underscore the indispensable roles of all Hox genes during the embryonic development of T. domestica. Our study sheds new light on the functional evolution of Hox genes in ametabolous insects and enhances our understanding of the genetic underpinnings of insect development and diversification.

The gut microbiota has been linked to the pathophysiology of inflammatory bowel disease (IBD). Current animal models are limited in the generation of germ-free animals to evaluate the roles of gut bacteria in intestinal health. Here, we used the honeybee (Apis mellifera) as a model animal to develop colitis-like gut permeability induced by dextran sodium sulfate (DSS) treatment. We found that DSS could increase gut permeability and compromise the mucosal barrier in honeybees, resulting in decreased survival rates, midgut elongation, and intestinal edema. DSS treatment upregulated the expression of wnt-1 and rhomboid and downregulated the pathways of cytochrome P450 (CYP) and the peroxisome proliferator-activated receptor signaling. Moreover, DSS disrupted the structure and functional profiles of the gut microbiota. Our results showed that medications reduced mortality and moderated leaky gut syndrome in DSS-treated bees. Notably, 5-aminosalicylic acid (5-ASA) could attenuate gut permeability in honeybees through activating PPARγ signaling, which mimics the human. Honeybees offer a promising experimental model for investigating the etiology of intestinal diseases and disentangling the roles of gut symbionts in intestinal health.

Many insects and their relatives are renowned for sophisticated compound eyes, which are also preserved in the fossil record. Yet there are other types of eyes, notably the so-called stemmata of holometabolans, such as beetles, bees, and butterflies. Stemmata are not as effective as compound eyes, except in some predatory larvae. Here we report three lacewing larvae with large forward-directed stemmata from Cretaceous Kachin amber, Myanmar. The stemmata are large relative to those of other fossil lacewing larvae, comparable to the simple eyes of modern larvae capable of image formation. The head is very wide in one larva, representing a new type of morphology as demonstrated by a quantitative comparison of the head and stylets of over 400 fossil and extant lacewing larvae. The arrangement of the exceptionally large stemmata of the larvae reported here provides stereoscopic vision. These new specimens demonstrate the convergent evolution of highly developed simple eyes in at least two additional lineages of lacewings, showcasing the enormous diversity of lacewing larvae in the Cretaceous.

Diapause is a programmed developmental arrest process in insects. Diapause can occur at various stages of insect development and is frequently restricted to a specific developmental stage within a single species. In Bombyx mori, embryonic diapause is elicited by the diapause hormone (DH) and DH receptor (DHR) in diapause strains. Nevertheless, the regulatory mechanism through which BmDHR functions as a G protein-coupled receptor (GPCR), to exert other physiological functions in nondiapause silkworms, remains unclear. In this study, we found that BmDHR had 7 alternative splice isoforms. A knockout experiment confirmed that BmDHR mediated the transduction of diapause signals. Interestingly, the loss of BmDHR caused partial precocious metamorphosis and an embryo-lethal phenotype in nondiapause silkworms. An assessment of global transcriptional patterns revealed that BmDHR knockout affected physiological responses induced by manifold cellular processes, including the Toll/immune deficiency (Imd), Wnt, insulin-like growth factor, Hedgehog and P38/mitogen-activated protein kinase (MAPK) signaling pathways. This study expands our knowledge of the physiological roles for DHR in insect growth and development.

The Drosophila melanogaster (fruit fly) misexpression suppressor of Ras 4 (MESR4) gene encodes a potential transcription factor and plays critical roles in various biological processes, including embryonic development, lipid metabolism, eye-antennal development, and germline stem cell differentiation. However, whether it is involved in modulating intestinal homeostasis remains elusive. In this study, we provide compelling evidence demonstrating that MESR4 is a bona fide regulator in preventing age-onset intestinal leakage and dysbiosis in adult flies. Mechanistically, MESR4 is predominantly located at the nucleus of intestinal cells and controls the expression of bag-of-marbles (bam), thereby restricting the excessive activation of immune deficiency signaling during aging. The silencing of Relish (Rel), which encodes a key transcription factor of the immune deficiency signaling pathway, reverses the beneficial effects of MESR4 in mediating intestinal barrier function and fly lifespan. Collectively, our studies uncover an undescribed function of Drosophila MESR4 in the maintenance of intestinal homeostasis and overall organismal fitness.