Insect Science最新文献

The Sterile Insect Technique (SIT) is an effective strategy for controlling insect pests, such as the Mediterranean fruit fly (Ceratitis capitata, Wiedemann). The effectiveness of the SIT depends on the ability of the sterile males to mate and their capacity to induce sterility in wild females. This study evaluated how the irradiation age affects their sexual performance, measured by the outcome of female remating events. Males of the GSS VIENNA 8^D53- were irradiated at eleven different ages, from 72 h before emergence (pupal stage) to 72 h after emergence (adult stage) and mated with wild females. These females were subsequently allowed to mate with fertile males from the fluorescent TSS VIENNA 8 1260. The presence of fluorescent offspring was used as indicator of second-male paternity. Results showed that males irradiated at post-emergence ages produced the lowest egg-to-pupae conversion rate, indicating a greater ability to prevent females from producing offspring after remating with a fertile male. In contrast, males irradiated at pre-emergence ages were associated with higher numbers of fluorescent offspring. Although no significant differences were found in mating competitiveness (RSI), the outcome of the remating showed differences in the effectiveness of initial matings. These findings highlight the importance of considering the age of flies at time of irradiation in mass-rearing protocols to enhance the efficacy of SIT programs targeting C. capitata and suggest that irradiating males later in their life cycle, such as adult stages or in pupae close to adult emergence, limit offspring if females remate with fertile males in the field.

The Sterile Insect Technique (SIT) is an environmentally friendly, sustainable pest control approach, which uses large-scale releases of sterile insects to suppress or eradicate target populations through infertile matings. The efficiency of SIT is enhanced by male-only releases requiring genetic sexing strains (GSSs) that are classically based on selectable recessive visible markers or temperature-sensitive lethal (tsl) mutations and a rescue by a wild-type allele translocated to the male-determining chromosome. The transfer of identified or designed temperature-sensitive alleles might allow the generation of neoclassical GSSs in additional SIT target species. By using precise genome-editing tools, such as CRISPR/Cas, the creation of specific mutations in target genes and the integration of a wild-type copy is feasible without the introduction of foreign DNA. This might ease regulation of neoclassical GSSs, since they are not considered transgenic. However, integration and expression of genes at male-determining loci or chromosomes is not reliably established. Therefore, additional strategies to link temperature-sensitive phenotypes to female development are required, which could be achieved by targeting genes involved in dosage compensation or sex determination. To create temperature-sensitive alleles, rational protein design using advanced modeling and prediction tools to evaluate and tailor the effect of mutations on protein stability and temperature sensitivity can be used. In addition, emerging synthetic biology strategies such as temperature-inducible N-degrons or temperature-sensitive inteins provide powerful tools to generate temperature sensitivity. Such approaches should enable conditional control over proteins causing female lethality or sex conversion and therefore promise straightforward generic approaches to generate GSSs for male-only production in SIT target species.

Knock-in efficiency via CRISPR/Cas9-based homology-directed repair (HDR) is low in lepidopteran insects due to predominance of knockout through non-homologous end joining (NHEJ) pathway. DNA ligase 4 (LIG4), a core protein of NHEJ complex and double-strand break (DSB) binding repair, is a promising target for enhancing HDR efficiency in diverse species. However, the role of Lig4 in modulating HDR efficiency in Plutella xylostella, a highly destructive pest of vegetable crops, remains unclear. The PxLig4 gene was identified from the P. xylostella genome with 4 conserved domains: ATP-dependent DNA ligase core-adenylation middle domain, ATP-dependent DNA ligase core‑adenylation N-terminal domain, ATP-dependent DNA ligase core‑adenylation C‑terminal domain, and BRCA1 C terminus domain. Multiple sequence alignment and phylogenetic analysis confirmed strong conservation of PxLig4 among Lepidoptera. Real-time quantitative polymerase chain reaction (RT-qPCR) analysis showed that PxLig4 was highly expressed in eggs, female adults, and male adults, particularly in the ovary, followed by the testis, fat body, and midgut tissues. A homozygous PxLig4 knockout line (ΔPxLig4) with a 2-bp deletion was successfully generated by using the CRISPR/Cas9 technique. ΔPxLig4 exhibited significant developmental and reproductive defects. A donor vector to knock in the enhanced green fluorescent protein (EGFP) gene at the eye color gene PxKmo was developed to assess knock-in efficiency. The knock-in efficiency in ΔPxLig4 was 2.86%, significantly higher than the 0.26% observed in the wild-type P. xylostella. These results implicate Lig4 as a supporting factor for NHEJ and demonstrate that suppression of PxLig4 enhances HDR efficiency in P. xylostella, providing a potential strategy to improve the efficiency of gene knock-in in insect pests.

Peptidoglycan recognition proteins (PGRPs), evolutionarily conserved pattern recognition receptors, act as receptors and regulators in insect Toll and IMD (immune deficiency) signaling pathways. Despite prior identification of silkworm long PGRP (PGRP-L) genes, their physiological roles remain poorly characterized. Here, we investigated the sequence features and expression patterns of silkworm PGRP-Ls, focusing on the role of PGRP-L1 in intestinal immunity and gut microbiota regulation. We identified and cloned 6 silkworm PGRP-L genes, and the proteins encoded by PGRP-L1, L4, L5, and L6 may function as nonamidolytic immune receptors predominantly expressed in the midgut. PGRP-L1 protein resides on the cell membrane of the midgut epithelium near the intestinal lumen and can directly bind to pathogens and peptidoglycans. Genetic and pathogen stimulation analyses revealed that PGRP-L1 knockout suppresses, while overexpression enhances, IMD pathway activation, specifically regulating antimicrobial peptides (AMPs) and Relish1 expression in the midgut. Under mulberry feeding, both PGRP-L1 knockout and overexpression significantly enhanced early larval growth; however, only individuals overexpressing PGRP-L1 maintained survival rates comparable to wild type individuals and improved economic traits. Additionally, PGRP-L1 knockout in artificial diet-fed larvae resulted in reduced microbial diversity, increased dominance of Enterococcus, and developmental arrest, whereas overexpression enhanced microbial richness and larval survival rates. These results established PGRP-L1 as a key regulator of gut immunity and microbiota homeostasis in silkworms and may operate through IMD-mediated AMP production and selective microbial control. Our findings provide insights into insect immune mechanisms and potential strategies for optimizing the gut health of economically important insects.

Diapause is a quintessential survival strategy orchestrated through animal-environment coevolution. Although extensive studies have been conducted using the silkworm, Bombyx mori, as the predominant diapause model, the molecular mechanisms underlying this process remain largely elusive. In this study, through transcriptomic profiling of serosal tissues comparing diapause-destined (DD) and nondiapause-destined silkworm eggs, we identified 2 790 upregulated and 2 791 downregulated genes in DD serosa. Functional enrichment analysis revealed significant associations of differentially expressed genes with key metabolic pathways, including amino sugar and nucleotide sugar metabolism, cell cycle regulation, and fatty acid elongation. Temporal expression profiling demonstrated stage-specific expression patterns of these differentially expressed genes across different diapause phases. CRISPR/Cas9-mediated knockout of the DD serosa-specific trehalose transporter gene (Tret1) reduced the trehalose consumption, concomitant with reduced sorbitol accumulation, and thus decreased the diapause incidence. Our findings provide novel insights into the serosa-mediated regulatory mechanisms governing embryonic diapause in B. mori.

Anastrepha fraterculus is a cryptic species complex with at least eight morphotypes distributed across the Americas. Among them, A. fraterculus sp.1, present in Argentina, is a major pest impacting fresh fruit production. Integrated pest management strategies, including chemical control and trapping, are currently employed to mitigate its effects. Genetic sexing strains of A. fraterculus sp.1 are being evaluated for use in sterile insect technique programs. To support traditional and emerging control methods, this study aimed to enhance the genomic understanding of this morphotype. Individual female and male samples were sequenced using long- and short-read technologies. The female genome (760 Mb) was de novo assembled into 58 scaffolds and the male genome (750 Mb) into 68 scaffolds, with BUSCO completeness scores of 98.8% and 98.7%, respectively. Synteny analysis revealed complete scaffolds of the five autosomes and enabled near-complete reconstruction of the X and Y chromosomes. Gene prediction identified 17 751 and 16 535 protein-coding genes (for female and male genomes, respectively), with repetitive regions representing 46% of both genomes. Additionally, the mitochondrial genome was fully assembled and annotated. This comprehensive genomic resource reveals candidate genes for functional studies, including gene editing and RNA interference, as successfully applied in related tephritid species. These findings lay the foundation for innovative, complementary biocontrol tools against A. fraterculus.

Iflaviruses are arthropod-infecting viruses classified in the family Iflaviridae. The most well-studied iflaviruses are responsible for deleterious overt (symptomatic) infections in economically important insect species like honeybees and silkworms. The fact that iflaviruses are also found in mass reared insects such as crickets and flies, makes their study relevant for the food and feed industries and for biological control applications (e.g., mass reared insects for sterile insect techniques). In recent years it was found that iflaviruses are not restricted to insects, but are widely spread in many arthropod species, often causing covert (asymptomatic) infections. Fitness costs may be associated with these covert infections, as seen in a variety of host species. In this work we review the latest research on iflaviruses in respect to host range, viral genome organization, cycle of infection, tissue tropism, virus transmission strategies, fitness costs and pathogenic effects of both covert and overt infections, host immune responses to iflavirus infections, interactions between iflaviruses and other microorganisms, and the effect of iflavirus infections on host behavior.

Genetic biocontrol methods are species-specific ways to suppress or modify pest insect populations to mitigate their economic or health impact. Successful genetic biocontrol often requires mass releases of only males of the target species. Reliable and cost-effective sex separation is a major bottleneck to the implementation of genetic biocontrol of many important species of agricultural and medical importance. Conditional selection is critical to resolving this major challenge. A diverse array of tools, such as the temperature-sensitive systems, the Gal4/UAS, QF/QUAS, and Tet-on/off bipartite systems, and the photoactivatable systems, have been established in various insect species. In this review, we focus on how various means of conditional expression have been used to achieve sex separation. We also describe other means of selection and counterselection to achieve sex separation without conditional gene expression. By providing examples across many species and discussing the strengths and weaknesses of each method, we hope to facilitate the design and application of conditional systems to improve genetic biocontrol of insect pests.

Southern rice black-streaked dwarf virus (SRBSDV) is a devastating plant reovirus transmitted by the white-backed planthopper (WBPH: Sogatella furcifera) in a persistent-propagative manner. However, the antiviral mechanisms in this insect vector remain poorly understood. Here, we identify sfCactin as a critical antiviral factor in WBPH, revealing its role in restricting viral replication through liquid-liquid phase separation (LLPS) and phosphorylation-dependent regulation. Evolutionary analysis shows that sfCactin shares conserved antiviral activity with Drosophila Cactin, suppressing replication of Drosophila C virus in heterologous systems. Mechanistically, sfCactin undergoes LLPS in vivo, forming dynamic nuclear condensates driven by its intrinsically disordered region 1 (IDR1), which contains an arginine/serine-rich domain and a coiled-coil domain. Unlike Drosophila Cactin, sfCactin lacks conserved phosphorylation sites (Ser₉₉/Ser₁₀₄) but interacts with phosphoglycerate kinase, which phosphorylates Thr₁₂₀ within IDR1. Phospho-mimetic mutations (T120D) enhance sfCactin's phase separation dynamics and antiviral activity, while non-phosphorylatable mutants (T120A) impair these functions. In S. furcifera, sfCactin expression is upregulated during SRBSDV infection, particularly in the midgut - a primary site of viral entry. RNAi-mediated knockdown of sfCactin significantly increases SRBSDV replication, acquisition, and transmission, highlighting its role in antiviral defense. This study uncovers a conserved yet evolutionarily adaptable mechanism by which Cactin employs LLPS and phosphorylation to combat viral infections in insect vectors, offering insights for managing plant virus transmission through vector immunity modulation.