Scholarly Literature

This is a database of scholarly literature that concentrates currently on natural and engineered selfish genetic elements (gene drives).  The latest are shown here.
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Conflicting Kinesin-14s in a single chromosomal drive haplotype

34899
Meghan J Brady, Anjali Gupta, Jonathan I Gent, et al.,  Genetics,  2025-06-06 08:37:38.
In maize, there are 2 meiotic drive systems that target large heterochromatic knobs composed of tandem repeats known as knob180 and TR-1. The first meiotic drive haplotype, abnormal chromosome 10 (Ab10) confers strong meiotic drive (∼75% transmission as a heterozygote) and encodes 2 kinesins: KINDR, which associates with knob180 repeats, and TRKIN, which associates with TR-1 repeats. Prior data show that meiotic drive is conferred primarily by the KINDR/knob180 system while the TRKIN/TR-1 system seems to have little or no role, making it unclear why Trkin has been maintained in Ab10 haplotypes. The second meiotic drive haplotype, K10L2, confers a low level of meiotic drive (∼51–52%) and only encodes the TRKIN/TR-1 system. Here, we used long-read sequencing to assemble the K10L2 haplotype and showed that it has strong homology to an internal portion of the Ab10 haplotype. We also carried out CRISPR mutagenesis to test the role of Trkin on Ab10 and K10L2. The data indicate that the Trkin gene on Ab10 does not improve drive or fitness but instead has a weak deleterious effect when paired with a normal chromosome 10. The deleterious effect is more severe when Ab10 is paired with K10L2: in this context, functional Trkin on either chromosome nearly abolishes Ab10 drive. Mathematical modeling based on the empirical data suggests that Trkin is unlikely to persist on Ab10. We conclude that Trkin either confers an advantage to Ab10 in untested circumstances or that it is in the process of being purged from the Ab10 population.

Evaluating the performance of three packing methods for long-distance transport of sterile adult Aedes albopictus males

34893
Mamai, W., Puggioli, A., Wallner, T. et al.,  Scientific Reports,  15. 2025-06-06 08:21:38.
This study evaluated the performance of three packing methods for long distance transport of sterile adult Aedes albopictus males, considering the specific effects of pupal vs. adult irradiation and two compaction methods. The results indicated that while transportation significantly impacted the quality of sterile males, all the three packing methods (IAEA V.1.0, IAEA V.2.0, and CAA) tested under simulated transportation durations of 25–48 h resulted in average mortality rates below 12%, with male escape rates ranging between 30 and 50% after a 24-h recovery period. The transported males were able to survive for about 2 days under stress conditions. Additionally, adult irradiation led to higher male survival and escape rates than pupal irradiation, for both before and after transportation. The study also found that stacked cups were more effective as compaction method than the square plastic boxes, despite having a reduced maximum transport capacity. Providing sterile males with 10% sugar for a 24-h recovery period after transportation, also played a role in enhancing escape rate and survival. Although Ae. albopictus prove to be more sensitive to packaging and shipping procedures compared to Aedes aegypti, this study provides valuable insights for developing and improving handling packing and shipping guidelines.

Intrinsically weak sex chromosome drive through sequential asymmetric meiosis

34889
Xuefeng Meng, Yukiko M. Yamashita,  Science Advances,  11. 2025-06-02 19:06:59.
Meiotic drivers are selfish genetic elements that bias their own transmission, violating Mendel’s Law of Equal Segregation. It has long been recognized that sex chromosome–linked drivers present a paradox: Their success in transmission can severely distort populations’ sex ratio and lead to extinction. This paradox is typically solved by the presence of suppressors or fitness costs associated with the driver, limiting the propagation of the driver. Here, we show that Stellate (Ste) in Drosophila melanogaster represents a novel class of X chromosome–linked driver that operates with an inherent mechanism that weakens its drive strength. Ste protein asymmetrically segregates into Y-bearing cells during meiosis I, subsequently causing their death. Unexpectedly, Ste segregates asymmetrically again during meiosis II, sparing half of the Y-bearing spermatids from Ste-induced defects, thereby weakening the drive strength. Our findings reveal a mechanism by which sex chromosome drivers avoid suicidal success.

Efficient CRISPR-Cas9-mediated genome editing of the cane toad (Rhinella marina)

34887
Michael Clark, Alexander T. Funk, Alex Paporakis, et al.,  bioRxiv,  2025-06-02 19:02:13.
Invasive species inflict major ecological, economic, social, and cultural harm worldwide, highlighting the urgent need for innovative and effective control strategies. Genome editing offers exciting possibilities for creating highly targeted control methods for invasive species. Here, we demonstrate CRISPR-Cas9 genome editing in the cane toad (Rhinella marina), one of Australia’s most notorious invasive species, by targeting the tyrosinase gene to produce albino phenotypes that provide clear visual markers for assessing editing efficiency. Microinjection of Cas9 protein and guide RNAs into one-cell zygotes resulted in 87.6% of mosaic larvae displaying nearly complete albinism, with 2.3% exhibiting complete albinism. For completely albino individuals, genomic analysis confirmed predominantly frameshift mutations or large deletions at the target site, with no wild-type alleles detected. Germline transmission rates reflected the extent of albinism in the mosaic adult, where we achieved maternal germline transmission rates of almost 100%. This technology, representing the first application of CRISPR-Cas9 in the Bufonidae family, opens possibilities for exploring both basic research questions and strategies for population control.

An animal toxin-antidote system kills cells by creating a novel cation channel

34881
Caro L, Wei AD, Thomas CA, Posch G, Uremis A, Franzi MC, et al.,  PLoS Biology,  23. 2025-06-02 18:36:53.
Toxin-antidote systems are selfish genetic elements composed of a linked toxin and antidote. The peel-1 zeel-1 toxin-antidote system in C. elegans consists of a transmembrane toxin protein PEEL-1 which acts cell autonomously to kill cells. Here we investigate the molecular mechanism of PEEL-1 toxicity. We find that PEEL-1 requires a small membrane protein, PMPL-1, for toxicity. Together, PEEL-1 and PMPL-1 are sufficient for toxicity in a heterologous system, HEK293T cells, and cause cell swelling and increased cell permeability to monovalent cations. Using purified proteins, we show that PEEL-1 and PMPL-1 allow ion flux through lipid bilayers and generate currents which resemble ion channel gating. Our work suggests that PEEL-1 kills cells by co-opting PMPL-1 and creating a cation channel.

Applying the Protective Precautionary Principle to the Ethical Use of Gene Drive Technology for Anopheles gambiae Suppression in Malaria Control

34879
Nucharee Wongsamut,  Journal of Applied Animal Ethics Research,  2025-06-02 18:16:36.
Malaria contributes to poverty and illness, which further hinder productivity and income generation. Therefore, combating malaria is crucial for breaking the vicious cycle of poverty. Genome editing technologies, such as gene drives designed to suppress Anopheles gambiae mosquito populations, the vector for malaria, have emerged as potential tools in this fight. However, a significant ethical question arises: under what conditions is the use of gene drive technology to suppress Anopheles gambiae mosquito populations justified? This article argues that the Protective Precautionary Principle can serve as a suitable framework for morally assessing such cases. Within this framework, the use of gene drive technology for Anopheles gambiae population suppression would be permissible for laboratory research only. This limited scope minimizes the risk of unforeseen negative consequences, particularly for disadvantaged populations who may have fewer resources to protect themselves from such effects.

The challenge of measuring mosquito flight performance: going beyond sterile insect technique and into transgenic and gene drive-based approaches

35311
Paola Najera, Christian E. Ogaugwu, Tyler F. Chan, et al.,  Open Biology,  15. 2025-06-01 10:32:43.
Invasive insects inflict global costs of more than 70 billion USD annually by destroying crops and spreading disease-causing pathogens. Sterile insect technique (SIT), an insect population control method, involves the irradiation or chemical sterilization of insects to produce sterile males that are mass-released. SIT has proven effective in reducing populations of the Mediterranean fruit fly, Mexican fruit fly and screwworm fly. In the past decade, efforts to improve SIT with transgenic approaches have increased, including the development of potentially highly invasive gene drive transgenes. Determining flight capability is vital to the success of any insect control programme, and various flight assays can be used to analyse insect dispersal, flight behaviour and the mechanics behind flight. However, traditional flight assays such as mark–release–recapture become more challenging with transgenic or gene drive arthropods due to ecological concerns, while assays such as wind tunnels or flight mills/arenas may not capture the full range of flight abilities. This review seeks to cover current flight assays and their limitations as well as the requirements for flight assays to establish comparative flight ability for genetically modified insects to better prioritize strains prior to any potential field-based releases.

Paratransgenesis: Overview, Current Perspectives, and Future Research Needs for Malaria Control

34874
Oziegbe, O., Okeke, C.C., Esho, D.O.,  Springer, Cham.,  2025-05-26 21:52:21.
Malaria is an insect-borne disease (IBD) that is responsible for significant human mortality and morbidity globally. Several effective vector and parasite control strategies have been considered to control malaria. However, paratransgenesis is a strategy targeted towards parasite development disruption rather than vector elimination which can potentially address insecticide resistance in mosquitoes. Genetically modified symbionts such as bacteria, fungi, or viruses secrete anti-plasmodial effector molecules that kill or inhibit the development of Plasmodium species without affecting the vector or the microorganism. Various anti-plasmodial effector molecules have been identified such as scorpin, a peptide from scorpion venom that acts by lysing the parasite, enolase- plasminogen interaction peptide (EPIP) which acts by inhibiting midgut invasion, A protein kinase (Akt) that acts by activating innate immune responses, and salivary gland and midgut peptide 1 (SMI) that acts by preventing binding to the parasite surface proteins. For this strategy to be successful, the selected symbiotic microorganism should be easy to culture and genetically manipulate, stable, as well as capable of producing effector molecules with anti-plasmodial activity while colonizing a wide range of the host species. Paratransgenesis presents a promising future for malaria control globally. However, its efficacy and safety as a malaria control strategy should be experimented with in large outdoor settings with more elaborate and collaborative studies carried out to sustain the approach in malaria-endemic countries.

Assessing the population genetic structure and demographic history of Anopheles gambiae and An. arabiensis at island and mainland populations in Uganda: Implications for testing novel malaria vector control approaches

34868
Rita Mwima, Tin-Yu J. Hui, Edward Lukyamuzi, et al,  bioRxiv,  2025-05-26 21:26:56.
This study collected 2918 Anopheles gambiae and 173 Anopheles. arabiensis across six populations from both the islands on Lake Victoria and mainland Uganda for amplicon sequencing. Large pairwise FST values were observed between the two species, indicating their divergence. We observed low but often significant FST values between the 6 An. gambiae populations, while between the An. arabiensis mainland populations, FST values were not significant. Principal Component Analysis also revealed strong genetic structure between the two species but did not provide a clear picture between populations within each species. We also found that mainland An. gambiae populations had higher within population genetic diversity than the islands’, while An. arabiensis had the lowest nucleotide diversity. Tajima’s D values were all negative, suggesting a recent population expansion. The islands An. gambiae populations had very low contemporary effective population sizes in the tens and hundreds, as estimated from linkage disequilibrium, while the mainland population sizes were consistently higher, in the thousands.

Optimizing larval mass-rearing techniques for Aedes mosquitoes: enhancing production and quality for genetic control strategies

34858
Wadaka Mamai, Cécile Brengues, Hamidou Maiga, et al,  Parasite,  32. 2025-05-26 20:56:36.
The quantity and quality of laboratory-reared insects are pivotal for the success of any sterile male-release program. Optimizing larval mass-rearing methods to enhance both production and quality in Aedes mosquitoes is essential to meet the growing demand from FAO/IAEA Member States for the sterile insect technique (SIT) as a component of area-wide integrated pest management to control or suppress disease vectors. This study was designed to identify the most effective feeding regime and schedule that maximize pupae production with a single tilt/sorting event and to evaluate an alternative larval-rearing unit. The results demonstrated that ingredient particle size, mosquito strain and feeding regime significantly influenced insect production and quality, underscoring the critical need to account for these factors in mass-rearing operations. A daily feeding regime of 0.17, 0.33, 0.67, 0.67 and 0.5 mg per larva was identified as optimal for both species (Ae. aegypti and Ae. albopictus) achieving up to 80 ± 2.5% male pupae recovery rate when sorted 48 h after the onset of pupation. Production outcomes were not compromised with the exclusion of feeding on Days 2 and 3. Furthermore, under the conditions of this study, the Wolbaki rack (Model WBK-P0003-V2) was shown to be sufficient for mass-rearing Aedes mosquitoes. Finally, a 4-day feeding regime was implemented in a field program on Reunion island, yielding similar pupae recovery rates and contamination as the reference regime, a significant step toward improving cost-efficiency and scaling-up the program. These findings provide valuable information for refining standard operating procedures (SOPs) for mass-rearing, thereby enhancing the efficiency and scalability of SIT programs.

Unstable laboratory Wolbachia strain w-Anga is negatively correlated with Plasmodium falciparum in wild malaria vectors

34856
Estelle, D.L., Jacques, G.E., Issiaka, S. et al.,  Scientific Reports,  15. 2025-05-26 20:48:59.
Spread of insecticides resistance threatens the control of malaria. In this context, biological control using an endosymbiotic bacterium Wolbachia is being explored as a complementary method for its control. However, for optimal use of this bacterium in biocontrol strategies, it is imperative to characterize it. So, Anopheles gambiae complex mosquitoes were collected, morphologically identified, then blood fed and gravid female mosquitoes oviposited individually. After oviposition, the species of parent was molecularly determined, along with their w-Anga infection status. Additionally, we performed 16SrRNA gene sequencing of w-Anga-positive mosquitoes to determine their phylogeny. Finally, we amplified gene encoding the circumsporozoite protein to determinate their Plasmodium falciparum infection status and assessed the stability of w-Anga transmission of positive females and their offspring. From the results obtained, our w-Anga strains cluster with other Wolbachia Supergroup B strains. However, the prevalence of Plasmodium falciparum infection was lower in Wolbachia-infected females (4.59%) than in those uninfected (22.02%). Furthermore, the transmission frequency of this bacterium in infected Anopheles coluzzii females of the F0 generation to F1 offspring was 10.64% and 16.67% from infected females of the F1 generation to F2 offspring. This study results will serve as preliminary data for the possible use of Wolbachia in malaria control.

Suppression of Aedes mosquito populations with the boosted sterile insect technique in tropical and Mediterranean urban areas

34854
Bouyer, J., Gil, D.A., Mora, I.P. et al.,  Scientific Reports,  15. 2025-05-26 20:31:16.
Aedes mosquitoes are the vectors of dengue viruses and other arboviruses, which threaten billions of people all over the world. The boosted sterile insect technique (boosted SIT) is a version of SIT in which irradiated sterile males also transmit a biocide to immature stages. We describe three field trials that were run in 2021: one against Aedes aegypti in La Reunion and two against Aedes albopictus in Spain, each using pyriproxyfen as a biocide. The relative density of adults (compared to their density in control sites: without sterile male release) decreased from 1.00 to 0.09, 95% credible interval [0.06, 0.15] (La Reunion, July) and to 0.02 [0.01, 0.03] and 0.11 [0.08, 0.16] (Spain, July and October). The success rate, corresponding to the proportion of traps with suppression greater than 80%, ranged from 0.43 to 0.71 in La Reunion, from 0.26 to 1.00, and from 0.50 to 0.70 in Spain. In Spain, suppression with boosted SIT was higher than with non-boosted SIT, in 2020 and 2022. This work is in line with the predictions of the model of a better efficacy of boosted SIT compared to SIT, together with partial protection from invasion of treated areas by fertile females, paving the way for larger-scale field trials.

A male-transmitted B chromosome undergoes strong meiotic drag in females

34850
Patrick M Ferree, Jayla Cummings, Emma Garman, et al,  bioRxiv,  2025-05-26 20:12:34.
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 unexpectedly low levels 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, suggesting that two PSR copies are lethal during development. Our findings reveal the successful inheritance of this selfish B chromosome involves a restriction to a single copy and hidden female meiotic drag in addition to its strong paternal drive.

Evaluating the impact on F1 sterility of tsetse pupae Glossina morsitans morsitans irradiated following short-term hypoxic conditioning

34848
Caroline K. Mirieri, Kiswend-sida M. Dera, Vanessa S. Dias, et al,  Insect Science,  2025-05-26 20:07:11.
The sterile insect technique (SIT) for tsetse involves releasing sterilized males to outcompete wild males in mating, resulting in nonviable progeny. Balancing optimum sterility and male quality is crucial. While irradiation in hypoxia or anoxia is routine for tephritid flies, its effect on tsetse, especially postrelease, is not well understood. We conducted experiments to understand the impact of irradiation in hypoxia on the sterility of the F1 generation of Glossina morsitans morsitans (Gmm). Initially, we tested the impact of 1-h preconditioning in hypoxia before irradiation and continued hypoxia up to 24, 48, and 72 h postirradiation on the emergence and flight propensity of treated males. We then assessed mating ability, survival, pupae per initial female (PPIF) and residual fertility of flies following irradiation at various doses after 1-h hypoxia conditioning. Finally, we determined the PPIF and residual fertility of the F1generation and the emergence of treated flies to the F2 generation. Results show that short-term conditioning (1 h) in hypoxia maintains or improves the qualities of the irradiated Gmm pupae. Regardless of irradiation in normoxia or hypoxia, higher residual fertility was observed in females than males in the F0 generation, and higher residual fertility in the F1 than the F0 generation for both sexes. However, the emergence rates of males decreased in the F2 generation compared with the F1 generation, a noteworthy finding for SIT programs for tsetse, implying diminishing populations of sterile flies.

Spiroplasma infection in colonized Glossina fuscipes fuscipes: impact on mass rearing and the sterile insect technique

34846
Kiswend-sida M. Dera, Daouda Tande Barro, Bénéwendé Aristide Kaboré, et al,  Insect Science,  2025-05-26 20:02:52.
Tsetse flies (Glossina spp.) can vector the parasites (Trypanosoma spp.) that cause the socioeconomically devastating neglected tropical diseases human and animal African trypanosomoses. In addition to this parasite, tsetse can harbor four genera of endosymbiotic bacteria, including Wigglesworthia, Sodalis, Wolbachia, and Spiroplasma, which are functionally crucial for the fly's physiological homeostasis and/or are potentially useful for the development of disease control strategies. Recent discoveries indicate that Spiroplasma infection negatively impacts tsetse fecundity. Conversely, housing the bacterium can benefit its fly host by making it unusually refractory to infection with parasitic African trypanosomes. In this study, we assessed the physiological impact of Spiroplasma infection on a laboratory colony of Glossina fuscipes fuscipes (Gff). For this purpose, two distinct Gff colonies were established: a Spi– colony that harbors a low Spiroplasma infection prevalence and a Spi+ colony that harbors a high Spiroplasma infection prevalence. Fitness parameters for both colonies revealed no significant differences in the length of larval development, adult eclosion rate, and flight propensity. However, flies from the Spi+ colony presented with lower fecundity and higher overall mortality than did individuals from the Spi– colony. Furthermore, males from the Spi– colony exhibited a competitive mating advantage over their Spi+ counterparts in a field cage setting. These findings have potential implications for the improvement of mass-rearing of Gff for sterile insect technique (SIT) applications.

Deliberate extinction by genome modification: An ethical challenge

35544
Gregory E. Kaebnick et al.,  Science,  388:707-709. 2025-05-15 10:35:25.
Among the ways that genome modification could be used to modify wild populations of organisms, the deliberate outcome of fully eradicating a species has received little critical attention. The lack of discussion leaves a difficult ethical question unresolved: When so much attention is given to the value of biodiversity and the conservation of species, what circumstances, paradoxically, might justify the deliberate, full extinction of a species? At least one species is now a preliminary candidate for full extinction, and cases under consideration for temporary suppression and local extinction might pose a risk of full extinction. We discuss three cases in which genome modification might be used to eradicate a species. Together, we argue, these cases suggest that deliberate full extinction might occasionally be acceptable, but only extremely rarely. The cases also highlight tensions within some widely held views about the conservation of species and the governance of genome editing.

Biased tertiary sex ratios enhance the efficacy of sex-ratio distorting genetic techniques to control invasive species

34843
Michael L. Jones, Ronald E. Thresher, Nicholas J. Bax,  Journal of Theoretical Biology,  2025-05-12 20:32:40.
Genetic biocontrol strategies are increasingly being developed and tested for reducing the effects of invasive species, and are highly likely to be an important tool of integrated pest management in the future. Included among such strategies are those that distort the sex ratio of the target species. Models used to forecast the efficacy of such strategies generally assume, implicitly, that the tertiary sex ratio of the target population is 50:50. We present evidence that this assumption is important, and that if the tertiary sex ratio is biased towards females, a sex-distorting construct introduced into the population that produces phenotypic males will become fixed at a level determined by the magnitude of the bias, even after further introductions cease. We show, first using a simple logistic population model, and second using a realistic simulation of an important aquatic invasive species – the sea lamprey Petromyzon marinus – how this effect can greatly increase the effectiveness of a sex-distorting construct at population suppression, but also increase the risk of such strategies due to reduced reversibility. We also present evidence that biased tertiary sex ratios might be present in many invasive species, particularly when their population sizes are low relative to environmental carrying capacity.

Overview of the sterile insect technique for Aedes aegypti in Lee County, Florida, USA

34841
Morreale, R., Stenhouse, S., Bajonero, J. et al.,  Infectious Diseases of Poverty,  14. 2025-05-12 20:10:08.
Lee County Mosquito Control District (LCMCD) is an independent taxing district that works to protect human health and improve quality of life in Lee County, Florida, USA. With local dengue transmission in southern Florida, LCMCD prioritized the control of Aedes aegypti. Due to the cryptic larval habitats of Ae. aegypti and insecticide resistance, effective control using conventional methods is difficult. Thus, the sterile insect technique (SIT) program, using X-ray irradiated male mosquitoes, was created to target Ae. aegypti. The goal of this program was to suppress Ae. aegypti through establishing a robust SIT program and performing a pilot study in the field to assess the impacts of SIT releases. The SIT program at LCMCD released sterile male Ae. aegypti from 2020 to 2022 in Captiva Island, Florida. The SIT program works within a larger Integrated Mosquito Management (IMM) framework and is not a standalone tool. The SIT program consists of nine employees, one of which is dedicated to quality assurance. Quality assurance assessments are performed routinely and periodically. Due to widespread destruction throughout Captiva and Sanibel Islands from Hurricane Ian in September 2022, the SIT pilot in Captiva Island was concluded and moved to Fort Myers, Florida. During the pilot study on Captiva Island, various lessons were learned and this knowledge has been applied to efforts in Fort Myers. LCMCD has established a successful SIT program to suppress populations of Ae. aegypti. Through connections with the International Atomic Energy Agency (IAEA) and the University of Florida, LCMCD received guidance from experts in the field to help ensure the program’s success. Stable funding through taxes levied specifically for mosquito control provided essential consistency, allowing the program to grow and evolve. Consistent trapping routines provided immense amounts of entomological data. Thoughtful and intentional community engagement was essential in ensuring acceptance of the SIT program in Lee County. Following the phased conditional approach suggested by IAEA, LCMCD has built an effective and resilient SIT program. The integration of the SIT as a tool of an area-wide mosquito control program is a feature that distinguishes LCMCD’s SIT program from others.

Differential elimination of marked sex chromosomes enables production of nontransgenic male mosquitoes in a single strain

34839
A. Compton, A. Sharma, M. Hempel, A. Aryan, J.K. Biedler,M.B. Potters, K. Chandrasegaran, C. Vinauger, & Z. Tu,  Proceedings of the National Academy of Sciences,  122. 2025-05-12 20:01:30.
Diverse genetic strategies are being pursued to control mosquito-borne infectious diseases. These strategies often rely on the release of nonbiting males to either reduce the target mosquito population or render them resistant to pathogens. Male-only releases are important as any contaminating females can bite and potentially transmit pathogens. Despite significant efforts, it remains a major bottleneck to reliably and efficiently separate males from females, especially when nontransgenic males are preferred. In the yellow fever mosquito Aedes aegypti, sex is determined by a pair of homomorphic sex chromosomes, with the dominant male-determining locus (the M locus) and its counterpart (the m locus) embedded in an M-bearing and an m-bearing chromosome 1, respectively. We utilized both naturally occurring and engineered sex-linked recessive lethal alleles (RLAs) to create sex separation strains for Ae. aegypti on the basis of differential elimination of marked sex chromosomes (DeMark). DeMark strains are self-sustaining and produce nontransgenic males that are readily separated from individuals carrying RLA- and transgene-marked m chromosomes. For example, the marked m chromosome in the heterozygous mother in some strains was only inherited by her female progeny due to RLA-mediated incompatibility with the M-bearing chromosome in the father, producing nontransgenic males and transgenic females, generation after generation. We further explore strategies to conditionally eliminate females that contain marked sex chromosomes. We also discuss DeMark designs that are applicable for efficient sex separation in organisms with well-differentiated X and Y chromosomes, such as the Anopheles mosquitoes.

Functional validation of a white pupae minimal gene construct in Ceratitis capitata

34835
Lucas Henrique Figueiredo Prates, Roswitha A. Aumann, Inga Sievers, et al.,  Insect Science,  2025-05-12 19:41:58.
Genetic sexing strains (GSS) are important tools for the sterile insect technique (SIT), an environmentally friendly and species-specific insect pest control method. GSS feature sex-specific phenotypes, enabling sex sorting in mass-rearing facilities and male-only releases, which significantly improve the cost-effectiveness and efficiency of SIT programs. In classical GSS, sex linkage of marker gene(s), such as white pupae (wp), is achieved through an irradiation-induced translocation between the marker-carrying autosome and the Y chromosome. However, this approach may render GSS males semisterile. The recently proposed neo-classical GSS concept suggests using genome editing to achieve sex linkage by directly inserting the wild-type marker allele onto the Y chromosome, potentially yielding GSS males with higher fertility. In this study, we examined the Ceratitis capitata wp gene as a genetic marker for the neo-classical GSS concept and developed a minimal, intronless version of this gene, termed mini-wp. We demonstrate that a single copy of mini-wp is sufficient to restore the wild-type brown puparium phenotype and is functional when integrated at various positions within the C. capitata genome, including the X chromosome. Due to its smaller size (4689 bp, including 2000 bp of putative promoter region) relative to the full wild-type wp allele (20868 bp), mini-wp may facilitate its precise insertion into the Y chromosome, representing an important step toward realizing neo-classical GSS. Furthermore, the methodology developed for designing and testing mini-wp in medfly may be adapted to other Tephritid species with an identified wp gene.

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