Keywords: Insects

Generating cisgenic sexing strains in insect pests

35435
Davydova, S., Liu, J., Kandul, N.P. et al.,  Communications Biology,  2026-02-05 18:20:56.
Insect pest population control via sterile insect technique markedly benefits from separation by sex prior to release. To simplify this process, traditional genetics has been deployed to develop genetic sexing strains (GSSs) for several disease vectors and agricultural pests of vast economic significance, although very few are applied in the field due to associated fitness costs and instability. In this study, we generated a method to engineer cisgenic GSS (CGSS) in insects. We use CRISPR/Cas9-mediated homology-directed repair to seamlessly translocate a sex-specific alternatively spliced intron into a dominant phenotypic gene generating a genetically stable strain that enables sex-sorting by eye. To achieve this feat, we use Ceratitis capitata as our model and relied on the sex-specifically spliced intron of its endogenous transformer gene, which we seamlessly inserted a copy into the pupal colouration white pupae gene. This minimal modification resulted in the generation of a homozygous strain we term IMPERIAL that was genetically and phenotypically stable where all female pupae are brown while male pupae are white with overall good fitness. By minimally editing the genome, our novel CGSS approach can be applied to other pests that may aid more efficient and economically suitable pest control.

A male-transmitted B chromosome undergoes strong meiotic drag in females of the jewel wasp Nasonia vitripennis

35373
Ferree PM, Cummings J, Garman E, Solomon J, Martinez KS,  PLoS Biol,  24. 2026-01-16 16:24:20.
Many organisms carry extra, non-essential chromosomes known as B chromosomes (Bs), which are selfishly transmitted at super-mendelian levels to offspring. This heightened transmission, termed drive, occurs during gametogenesis, usually in one of the two parents. In some cases, Bs can experience an opposing process, drag, which reduces their transmission. If these processes occur together in the same organism, one in each parental sex, then they may facilitate the spread of Bs while countering their accumulation in the genome to harmful levels. While previous studies have elucidated mechanistic aspects of B drive, little is known about drag or other factors that govern the inheritance of these selfish genetic elements. Here, we examined the inheritance of Paternal Sex Ratio (PSR), a single-copy B in the jewel wasp, Nasonia vitripennis, which is transmitted paternally to offspring. PSR drives by converting female-destined embryos into PSR-transmitting males. Using genetic manipulation, we produced exceptional PSR-carrying females, which were used to assess B transmission potential. We found that females transmit PSR at an unexpectedly low level compared to univalent chromosomes in other organisms. This reduced transmission stems from remarkable loss of PSR from the egg’s nucleus upon entry into meiosis, an effect that may be caused by an absence of microtubule-based spindle fibers in meiosis I-arrested wasp eggs. We also found that PSR is strictly limited to a single copy per genome, likely because wasps having two PSR copies die during development. Our findings reveal the successful inheritance of this selfish B chromosome involves its restriction to a single copy and hidden female meiotic drag in addition to strong paternal drive.

Identification and evaluation of two testis-specific serine/threonine kinase genes from multi-tissue transcriptomes as potential genetic targets of sterile insect technique in Zeugodacus tau

35439
Weijun Li, Cuikang Xu, Hongshi Chen, et al.,  Pest Management Science,  2026-01-15 18:32:40.
Zeugodacus tau (Walker) is a notorious agricultural pest causing significant economic losses in vegetable production for many years. Sterile insect technique (SIT) has emerged as an environmentally sustainable pest management strategy. However, discovery of molecular targets applicable for SIT implementation in Z. tau still constitutes a significant research gap. We conducted comparative transcriptome analysis of four male tissues (midgut, Malpighian tubules, fat body, and testis), identifying 9653 differentially expressed genes (DEGs) with predominant testis enrichment. Bioinformatics screening revealed 3020 testis-specific highly expressed genes showing significant functional enrichment in cytoplasmic translation, cytosolic ribosome assembly, and oxidoreductase activity. Quantitative real-time PCR (qRT-PCR) assay was utilized to confirm 10 testis-specific genes, including two serine/threonine kinases (ZtTSSK1 and ZtTSSK3) which were significantly enriched in spermatid development. Fluorescence in situ hybridization (FISH) localized the two genes specifically to the transformation zone of Z. tau testis. Functional characterization via RNAi bioassay demonstrated that suppression of ZtTSSKs expression levels reduced spermatozoa number and impaired male fertility. These results establish ZtTSSKs as crucial regulators of male fertility in Z. tau and identify them as potential molecular targets for developing SIT-based interventions against this economically significant pest.

Suitability of a chilled environmental box of the Precision X-RAD 320 cabinet style irradiator for the irradiation of mosquitoes and tsetse in the context of the sterile insect technique

35276
Hanano Yamada, Bénéwendé Aristide Kaboré, Samar Eisa, et al.,  Journal of Economic Entomology,  2025-11-03 11:17:02.
A cabinet-style small animal X-irradiator outfitted with an environmental chamber which can provide a consistent, chilled environment during irradiation was tested to sterilize the human and animal disease vectors Aedes aegypti Linnaeus (Diptera: Culicidae), Anopheles arabiensis Patton (Diptera: Culicidae), Glossina palpalis gambiensis Vanderplank (Diptera: Glossinidae) in the frame of the sterile insect technique (SIT). The environmental chamber enables the irradiation of immobilized, compacted adult insects avoiding mechanical damage incurred by movement and, thereby, maintaining better insect quality. For the species tested, there was no significant difference in dose response when irradiating late-stage pupae or adults, and chilling at 7 °C did not affect irradiation outcome in terms of sterility induced. The X-irradiator was shown to be effective and suitable for the sterilization of these important target species of the SIT and offers a practical means to sterilize insects at the adult stage which require chilling for immobilization.

Impact of long-term mass-rearing on the genetic structure of tsetse fly Glossina palpalis gambiensis colonies

35273
Kiswend-sida M. Dera, Soumaïla Pagabeleguem, Tito Tresor Melachio Tanekou, et al.,  Insect Science,  32. 2025-11-02 17:49:38.
Tsetse flies are the sole cyclic vectors of African trypanosomes, which cause human and animal African trypanosomiases in Africa. Tsetse fly control remains a promising option for disease management. The sterile insect technique (SIT) stands as an environmentally friendly tool to control tsetse populations. SIT requires the mass-rearing of competent sterile males to mate with wild females. However, long-term colonization might affect the genetic structure of the reared flies. This study investigated the genetic structure of four Glossina palpalis gambiensis colonies of different ages: two originating from Senegal (SEN and ICIRSEN) and two from Burkina Faso (CIR and IBD). Samples from these colonies were genotyped at ten microsatellite loci, followed by downstream population genetic analyses. The results show that the two colonies from Burkina Faso collected from close sites (∼20 km apart) over 45-year interval retained the same genetic background (FST_CIR∼IBD ≈ 0, P-value = 0.47). These flies were however, genetically different from those from the Senegal colonies (FST_CIR∼SEN ≈ 0.047; FST_IBD∼SEN ≈ 0.058, P-value = 10−4). Moreover, no significant difference was detected in the gene diversity of the CIR and IBD colonies, with HS values of 0.650 and 0.665, respectively. The inbreeding coefficient showed that all four colonies where under Hardy–Weinberg equilibrium, with FIS values of 0.026, 0.012, −0.064, and 0.001, for CIR, IBD, ICIRSEN, and SEN, respectively. Furthermore, no sign of a recent bottleneck was identified in tsetse samples from any of the four colonies. The results suggest that long-term mass-rearing of tsetse flies has no significant impact on their genetic background and diversity.

Selection, counterselection, and conditional gene expression for genetic biocontrol of insects

35249
Melanie Hempel, Zhijian Tu,  Insect Science,  2025-10-16 09:29:04.
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.

The impact of sterile insect technique processes on the performance of tephritid flies

35190
Mayren Sánchez-Rosario, Jorge Toledo, Walther Enkerlin,  Insect Science,  2025-09-29 09:49:25.
The sterile insect technique (SIT) is a pest control method that has been successful in controlling various species of fruit flies of economic importance worldwide. However, SIT procedures can affect the performance of mass-reared sterile fruit flies, compromising the SIT effectiveness. This review aims to identify and analyze the adverse effects associated with each step of the SIT. Special emphasis is placed on identifying critical points in the SIT process that compromise the quality and highlighting the stages that require greater optimization to improve the effectiveness of the technique. We reviewed the main scientific findings that document the impact of domestication, mass-rearing, irradiation, handling, and release on the biology, ecology, behavior, and genetic makeup of sterile males, and how they affect the performance of sterile males under natural conditions, and the effectiveness of the SIT. Although all stages of the Sterile Insect Technique (SIT) impose some degree of compromise on insect performance, domestication and mass-rearing have the most profoundly negative impact on the field performance of sterile fruit flies. As the initial and most influential stages, they largely determine the overall quality and competitiveness of released insects, exerting a stronger impact than any subsequent SIT component.

The role of the transformer gene in sex determination and its employment in CRISPR/Cas9-based homing gene drive in the global fruit pest Drosophila suzukii

35185
Dan Deng, Xueying Yi, Wen Wen, Liuqing He, Wei Peng,  Insect Biochemistry and Molecular Biology,  184. 2025-09-29 08:45:13.
Sex determination of Diptera is established by the cascade genes such as transformer (tra), though the primary signals for sex determination differ among different insects. Here, we report the isolation, expression and function of tra gene in an invasive pest, Drosophila suzukii, and study the potential use of the D. suzukii tra (Dstra) gene in CRISPR/Cas9-based homing gene drive for genetic-based pest management. The Dstra gene is highly conserved in structure and has a sex-specific transcript. To test the function of this gene in sex determination, Dstra dsRNA was injected into embryos. Almost all XX embryos developed into masculinized phenotypic male adults with intersex morphology. Abnormal ovaries were revealed in XX pseudomales upon dissection. Based on the necessary role of Dstra for female development, we developed and evaluated a homing gene drive that targets Dstra in D. suzukii. The drive component consisting of multiplex Dstra single guide RNAs and Cas9 with Dsvasa promoter was introduced into the Dstra locus. Abnormal development of both the external genitalia and gonads was observed in G0 and G1 chromosomal female adults that expressed the male-specific doublesex (dsx) transcript. Interestingly, knocking out Dstra led to significantly reduced fertility in adults of corresponding sex and moderate transmission rates of the DsRed gene (63.54 %) were observed. Our results not only confirm the conserved function of the Dstra gene in sex determination, but also highlight the potential of sex conversion-based suppression gene-drive strategy targeting the Dstra gene in controlling of D. suzukii populations.

Leveraging Sex Determination Systems for Genetic Biocontrol of Dipteran Pests

35178
Maxwell J. Scott, Zhijian Tu,  Current Opinion in Insect Science,  2025-09-26 14:24:25.
Genetic biocontrol is an increasingly important way to suppress insect pest populations and to mitigate their economic and health impact. One key advantage is that it is species-specific as it relies on mating of released males with wild females to either suppress or modify populations. The latter is through rendering females incompetent at disease transmission. Sex separation is critical to ensure the efficiency of these control programs, and it is essential in the case of vector control to avoid releasing females that can transmit pathogens. Modern genetic methods provide the opportunity to target or manipulate components of the sex determination systems to facilitate genetic biocontrol with new means to effectively accomplish sex-specific selection, lethality, or sterility. For example, sex-specific splicing elements in genes in the sex determination pathway are used to produce sex-specific markers. Sex-linked recessive lethal alleles are used to differentially eliminate the transgene-marked sex chromosome from males to produce non-transgenic males. Knocking out or knocking down sex-specific isoforms of genes in the sex determination pathway is employed to confer female-specific lethality or sterility. Sex determination pathways and sex chromosomes are also targeted for gene drives that suppress pest populations by introducing extreme sex ratio biases. Here we review these and other recent advances on the genetic technologies for pest control that have benefited from knowledge of sex determination systems in Diptera.

Single-cell consequences of X-linked meiotic drive in stalk-eyed flies

35155
Price PD, Parkus SM, Lloyd VJ, Alston BT, Bradshaw SL, Bates S, et al.,  PLoS Genet,  21. 2025-09-22 10:33:47.
Meiotic drivers, a class of selfish gene, are frequently located on sex chromosomes and have dramatic impacts on gamete development. However, our understanding of their molecular consequences for gamete production and sex chromosome regulation has focused on a handful of model organisms. In this study, we use single-cell RNA-sequencing approaches to produce a single-cell atlas of the testis of the stalk-eyed fly, Teleopsis dalmanni. This species harbours an X-linked meiotic driver where drive males produce more than 90% female offspring. First, we generate a comprehensive profile of the cellular and transcriptional landscape of spermatogenesis. We show limited evidence for meiotic sex chromosome inactivation and unique patterns of dosage compensation across spermatogenesis, relative to both other dipterans and insects in general. Finally, by comparing single-cell expression data between standard and drive males, we show that although there are significant differences in genome regulation, broad expression dynamics in the testis are conserved in the presence of meiotic drive. Notably, we highlight key genes with perturbed expression as a potential consequence of the disruption of spermatogenesis by the X-linked meiotic driver.

Field Performance of a Self-Limiting, Genetically Engineered Fall Armyworm for Biological Pest Management

35180
Reavey Catherine E. , Domingues Felipe A. , Ercit Kyla, et al.,  Sec. Pest Management,  7. 2025-08-21 14:28:43.
The fall armyworm is one of the most globally significant agricultural pests, damaging corn, sorghum and other crops central to food production. It has developed resistance to several classes of chemical insecticides and, more recently, insect-resistant ‘Bt’ biotech corn varieties. As Bt varieties constitute the great majority of corn acreage in Brazil, proactive resistance management strategies are required to protect the durability of insecticidal efficacy of those cultivars. Previously, we reported on the development of a ‘self-limiting’ fall armyworm strain, called OX5382G, which – after release in the field – is engineered to suppress populations of fall armyworm and manage resistance to Bt crops in treated populations of this pest. Here, we build on this work by carrying out contained studies to empirically assess the pest suppression and resistance management benefits of releasing OX5382G males. We also report on the first open field releases of the OX5382G self-limiting strain in Brazil. Following commercial biosafety approval of this strain by Brazilian government regulators, deployment-relevant OX5382G male performance was then assessed in larger, operational trials in Brazil. Pest suppression and resistance management benefits were demonstrated in contained studies. In the first open field releases, OX5382G males showed comparable performance with wild-type counterparts in terms of dispersal and mating ability. In the subsequent larger, farm-scale trials in Brazil, OX5382G mated effectively in the field and we demonstrated that relatively modest release rates can achieve over-flooding ratios expected to exert suppression and/or resistance management. All assessments to date suggest that self-limiting fall armyworm is a promising future tool for managing fall armyworm and extending the durability of Bt crops’ effectiveness against damaging lepidopteran pests.