Scholarly Literature
This is an aggregation of scholarly literature from peer-reviewed journals, bioRxiv , medRxiv and arXiv preprint servers focused on natural and engineered selfish genetic elements and genetic biocontrol. New citations are added as they appear. This content is intended for anyone interested in the scholarly literature on gene drive and genetic biocontrol.
Unravelling transmission ratio distortion across the bovine genome: identification of candidate regions for reproduction defects
26542S. Id-Lahoucine, J. Casellas, A. Suárez-Vega, P. A. S. Fonseca, F. S. Schenkel, M. Sargolzaei and A. Cánovas, BMC Genomics, 24:383. 2023-07-08 08:21:35.
Our results revealed the importance of implementing different TRD parameterizations to capture all types of distortions and to determine the corresponding inheritance pattern. Novel candidate genomic regions containing lethal alleles and genes with functional and biological consequences on fertility and pre‑ and post‑natal viability were also identified, providing opportunities for improving breeding success in cattle
Routes of Introduction of Anopheles gambiae Into Remote Islands in the Indian Ocean
26612R. E. Ditter, M. Campos, M. W. Crepeau, J. Pinto, A. Toilibou, Y. Amina, Y. Lee, A. J. Cornel and G. C. Lanzaro, 2023-07-07 13:23:28.
The malaria vector Anopheles gambiae s.s., is a primary malaria vector throughout sub-Saharan Africa including the islands of the Comoros archipelago (Anjouan, Grande Comore, Mayotte and Mohéli). These islands are located at the northern end of the Mozambique Channel in eastern Africa. Previous studies have shown a relatively high degree of genetic isolation between island and mainland populations of A. gambiae, but the origin of the island populations remains unclear. Here, we analyzed phylogenetic relationships among island and mainland populations using complete mitochondrial genome sequences of individual A. gambiae specimens. We investigated the source population of A. gambiaefor each island, determined the number of introductions and estimated when they occurred, and explored evidence for contemporary gene flow between island and mainland populations. Phylogenetic analysis and haplotype networks were constructed from mitogenome sequences of 258 A. gambiae from the four islands. In addition, 112 individuals from seven countries across sub-Saharan Africa and Madagascar were included to identify potential source populations. Our results suggest that introduction events of A. gambiae into the Comoros archipelago were rare and recent events and that there is no evidence of contemporary migration between the islands and mainland Africa. This study further supports the suitability of these oceanic islands as appropriate sites for conducting field trial releases of genetically engineered mosquitoes (GEMs).
Threshold dynamics of a stochastic mathematical model for Wolbachia infections
26546J. Yang, Z. Chen, Y. Tan, Z. Liu and R. A. Cheke, Journal of Biological Dynamics, 17:2231967. 2023-07-07 08:51:13.
A stochastic mathematical model is proposed to study how environmental heterogeneity and the augmentation of mosquitoes with Wolbachia bacteria affect the outcomes of dengue disease. The existence and uniqueness of the positive solutions of the system are studied. Then the V-geometrically ergodicity and stochastic ultimate boundedness are investigated. Further, threshold conditions for successful population replacement are derived and the existence of a unique ergodic steady-state distribution of the system is explored. The results show that the ratio of infected to uninfected mosquitoes has a great influence on population replacement. Moreover, environmental noise plays a significant role in control of dengue fever.
The Effect of X-ray Irradiation on the Fitness and Field Adaptability of the Codling Moth: An Orchard Study in Northeast China
26544J. Zhang, S. Huang, S. Zhao, X. Wang, X. Yang, H. Zhao, P. Gao, Y. Li and X. Yang, Insects, 14. 2023-07-07 08:43:03.
The codling moth, Cydia pomonella (L.), is an invasive agricultural pest of pome fruits and walnuts in China that threatens the apple industry in the Loess Plateau and Bohai Bay; it has developed resistance to many insecticides. Sterile insect technique (SIT) combined with area-wide integrated pest management (AW-IPM) can reduce the risk of resistance to insecticides and effectively control some insect pest species. Our previous laboratory experiment found that irradiation with 366 Gy of X-ray caused the males of the codling moth to become sterile. However, the sterility and adaptability of males after being irradiated with 366 Gy X-ray in the field are still unclear. In this study, we investigated the effect of X-ray irradiation on the fitness of male adults that emerged from pupae irradiated with 366 Gy to explore their adaptability and mating competitiveness, and to examine the effect of releasing sterile male insects in orchards in northeast China on the fruit infestation rate of the Nanguo pear. The results showed that 366 Gy of X-ray irradiation significantly reduced the mating competitiveness of males and the hatching rate of the eggs laid by females pairing with sterile males. Meanwhile, the lifespan of the sterile male moths was significantly shorter than that of the normal ones in the field. A pilot test showed that the release twice of sterile male moths in the orchards had no significant effect on the fruit infestation rate. Our field experiments provide a scientific basis for the further optimization of the SIT technology program for controlling C. pomonella.
The evolutionary history of Drosophila simulans Y chromosomes reveals molecular signatures of resistance to sex ratio meiotic drive
26469C. Courret, D. Ogereau, C. Gilbert, A. M. Larracuente and C. Montchamp-Moreau, Mol Biol Evol, 2023-07-04 07:54:47.
The recent evolutionary history of the Y chromosome in Drosophila simulans, a worldwide species of Afrotropical origin, is closely linked to that of X-linked meiotic drivers (Paris system). The spread of the Paris drivers in natural populations has elicited the selection of drive resistant Y chromosomes. To infer the evolutionary history of the Y chromosome in relation to the Paris drive, we sequenced 21 iso-Y lines, each carrying a Y chromosome from a different location. Among them, 13 lines carry a Y chromosome that is able to counteract the effect of the drivers. Despite their very different geographical origins, all sensitive Y's are highly similar, suggesting that they share a recent common ancestor. The resistant Y chromosomes are more divergent and segregate in four distinct clusters. The phylogeny of the Y chromosome confirms that the resistant lineage predates the emergence of Paris drive. The ancestry of the resistant lineage is further supported by the examination of Y-linked sequences in the sister species of D. simulans, D. sechellia, and D. mauritiana. We also characterized the variation in repeat content among Y chromosomes and identified multiple simple satellites associated with resistance. Altogether, the molecular polymorphism allows us to infer the demographic and evolutionary history of the Y chromosome and provides new insights on the genetic basis of resistance.
Meiotic drive of noncentromeric loci in mammalian meiosis II eggs
26477D. M. Silva and T. Akera, Curr Opin Genet Dev, 81:102082. 2023-07-03 08:21:48.
The germline produces haploid gametes through a specialized cell division called meiosis. In general, homologous chromosomes from each parent segregate randomly to the daughter cells during meiosis, providing parental alleles with an equal chance of transmission. Meiotic drivers are selfish elements who cheat this process to increase their transmission rate. In female meiosis, selfish centromeres and noncentromeric drivers cheat by preferentially segregating to the egg cell. Selfish centromeres cheat in meiosis I (MI), while noncentromeric drivers can cheat in both meiosis I and meiosis II (MII). Here, we highlight recent advances on our understanding of the molecular mechanisms underlying these genetic cheating strategies, especially focusing on mammalian systems, and discuss new models of how noncentromeric selfish drivers can cheat in MII eggs.
Steering and controlling evolution — from bioengineering to fighting pathogens
26463M. Lässig, V. Mustonen and A. Nourmohammad, Nature Reviews Genetics, 2023-07-03 07:31:07.
Control interventions steer the evolution of molecules, viruses, microorganisms or other cells towards a desired outcome. Applications range from engineering biomolecules and synthetic organisms to drug, therapy and vaccine design against pathogens and cancer. In all these instances, a control system alters the eco-evolutionary trajectory of a target system, inducing new functions or suppressing escape evolution. Here, we synthesize the objectives, mechanisms and dynamics of eco-evolutionary control in different biological systems. We discuss how the control system learns and processes information about the target system by sensing or measuring, through adaptive evolution or computational prediction of future trajectories. This information flow distinguishes pre-emptive control strategies by humans from feedback control in biotic systems. We establish a cost–benefit calculus to gauge and optimize control protocols, highlighting the fundamental link between predictability of evolution and efficacy of pre-emptive control.
Novel Conservation Strategies to Conserve Australian Marsupials
28144S. Legge, M. Hayward and A. Weeks, American and Australasian Marsupials, 2023-07-01 10:36:55.
The Australian marsupial fauna has been devastated in the past 250 years, mainly due to impacts from invasive mammalian predators (cats and foxes), although other threats such as invasive herbivores, habitat loss and fragmentation, changes to fire regimes, and now climate change have played a role. The profound and ongoing impact of invasive predators has driven substantial research and management innovation. Australia has been at the forefront of developing approaches to reduce the density and impacts of introduced predators and implementing novel and ambitious species conservation programs. A large and growing network of islands and mainland fenced areas, free of introduced predators (“havens”), has been critical for avoiding further species extinctions. Outside these havens, advances in toxin presentation and deployment have enabled cat and fox densities to be reduced over large areas. Substantial research and field trials have been carried out to understand how predator-prey interactions, and habitat quality management, can be used to reduce predation impacts on susceptible native species. Synthetic biology offers new opportunities to manage introduced predators, including potentially by using gene drives. Finally, the attenuation of the formerly large continuous ranges of many species to small, isolated population remnants (because of predation or other reasons) has also driven research and improvements in genetic and metapopulation management that will increase the chance of population persistence in the longer term. However, unless Australia continues to invest in research and innovative conservation actions, the plight of its priceless marsupial fauna will remain perilous.
Wolbachia -mediated resistance to Zika virus infection in Aedes aegypti is dominated by diverse transcriptional regulation and weak evolutionary pressures
26604E. C. Boehm, A. S. Jaeger, H. J. Ries, D. Castañeda, A. M. Weiler, C. C. Valencia, J. Weger-Lucarelli, G. D. Ebel, S. L. O'Connor, T. C. Friedrich, M. Zamanian and M. T. Aliota, bioRxiv, 2023-06-26 13:09:35.
A promising candidate for arbovirus control and prevention relies on replacing arbovirus-susceptible Aedes aegypti populations with mosquitoes that have been colonized by the intracellular bacterium Wolbachia and thus have a reduced capacity to transmit arboviruses. This reduced capacity to transmit arboviruses is mediated through a phenomenon referred to as pathogen blocking. Pathogen blocking has primarily been proposed as a tool to control dengue virus (DENV) transmission, however it works against a range of viruses, including Zika virus (ZIKV). Despite years of research, the molecular mechanisms underlying pathogen blocking still need to be better understood. Here, we used RNA-seq to characterize mosquito gene transcription dynamics in Ae. aegypti infected with the w Mel strain of Wolbachia that are being released by the World Mosquito Program in Medellín, Colombia. Comparative analyses using ZIKV-infected, uninfected tissues, and mosquitoes without Wolbachia revealed that the influence of w Mel on mosquito gene transcription is multifactorial. Importantly, because Wolbachia limits, but does not completely prevent, replication of ZIKV and other viruses in coinfected mosquitoes, there is a possibility that these viruses could evolve resistance to pathogen blocking. Therefore, to understand the influence of Wolbachia on within-host ZIKV evolution, we characterized the genetic diversity of molecularly barcoded ZIKV virus populations replicating in Wolbachia -infected mosquitoes and found that within-host ZIKV evolution was subject to weak purifying selection and, unexpectedly, loose anatomical bottlenecks in the presence and absence of Wolbachia . Together, these findings suggest that there is no clear transcriptional profile associated with Wolbachia -mediated ZIKV restriction, and that there is no evidence for ZIKV escape from this restriction in our system. AUTHOR SUMMARY: When Wolbachia bacteria infect Aedes aegypti mosquitoes, they dramatically reduce the mosquitoes' susceptibility to infection with a range of arthropod-borne viruses, including Zika virus (ZIKV). Although this pathogen-blocking effect has been widely recognized, its mechanisms remain unclear. Furthermore, because Wolbachia limits, but does not completely prevent, replication of ZIKV and other viruses in coinfected mosquitoes, there is a possibility that these viruses could evolve resistance to Wolbachia -mediated blocking. Here, we use host transcriptomics and viral genome sequencing to examine the mechanisms of ZIKV pathogen blocking by Wolbachia and viral evolutionary dynamics in Ae. aegypti mosquitoes. We find complex transcriptome patterns that do not suggest a single clear mechanism for pathogen blocking. We also find no evidence that Wolbachia exerts detectable selective pressures on ZIKV in coinfected mosquitoes. Together our data suggest that it may be difficult for ZIKV to evolve Wolbachia resistance, perhaps due to the complexity of the pathogen blockade mechanism.
Impacts of sex ratio meiotic drive on genome structure and function in a stalk-eyed fly
26279J. A. Reinhardt, R. H. Baker, A. V. Zimin, C. Ladias, K. A. Paczolt, J. H. Werren, C. Y. Hayashi and G. S. Wilkinson, Genome Biology Evolution, 2023-06-26 10:49:44.
Stalk-eyed flies in the genus Teleopsis carry selfish genetic elements that induce sex ratio meiotic drive (SR) and impact the fitness of male and female carriers. Here, we assemble and describe a chromosome-level genome assembly of the stalk-eyed fly, Teleopsis dalmanni, to elucidate patterns of divergence associated with SR. The genome contains tens of thousands of transposable element (TE) insertions and hundreds of transcriptionally and insertionally active TE families. By resequencing pools of SR and ST males using short and long-reads, we find widespread differentiation and divergence between XSR and XST associated with multiple nested inversions involving most of the sex ratio haplotype. Examination of genomic coverage and gene expression data revealed seven X-linked genes with elevated expression and coverage in SR males. The most extreme and likely drive candidate involves an XSR-specific expansion of an array of partial copies of JASPer, a gene necessary for maintenance of euchromatin and associated with regulation of TE expression. In addition, we find evidence for rapid protein evolution between XSR and XST for testis expressed and novel genes, i.e. either recent duplicates or lacking a dipteran ortholog, including an X-linked duplicate of maelstrom, which is also involved in TE silencing. Overall, the evidence suggests that this ancient XSR polymorphism has had a variety of impacts on repetitive DNA and its regulation in this species.
MGSurvE: A framework to optimize trap placement for genetic surveillance of mosquito population
26616C. H. Sánchez, D. L. Smith and J. M. Marshall, bioRxiv, 2023-06-23 13:35:51.
Genetic surveillance of mosquito populations is becoming increasingly relevant as genetics-based mosquito control strategies advance from laboratory to field testing. Especially applicable are mosquito gene drive projects, the potential scale of which leads monitoring to be a significant cost driver. For these projects, monitoring will be required to detect unintended spread of gene drive mosquitoes beyond field sites, and the emergence of alternative alleles, such as drive-resistant alleles or non-functional effector genes, within intervention sites. This entails the need to distribute mosquito traps efficiently such that an allele of interest is detected as quickly as possible - ideally when remediation is still viable. Additionally, insecticide-based tools such as bednets are compromised by insecticide-resistance alleles for which there is also a need to detect as quickly as possible. To this end, we present MGSurvE (Mosquito Gene SurveillancE): a computational framework that optimizes trap placement for genetic surveillance of mosquito populations such that the time to detection of an allele of interest is minimized. A key strength of MGSurvE is that it allows important biological features of mosquitoes and the landscapes they inhabit to be accounted for, namely: i) resources required by mosquitoes (e.g., food sources and aquatic breeding sites) can be explicitly distributed through a landscape, ii) movement of mosquitoes may depend on their sex, the current state of their gonotrophic cycle (if female) and resource attractiveness, and iii) traps may differ in their attractiveness profile. Example MGSurvE analyses are presented to demonstrate optimal trap placement for: i) an Aedes aegypti population in a suburban landscape in Queensland, Australia, and ii)an Anopheles gambiae population on the island of São Tomé, São Tomé and Príncipe. Further documentation and use examples are provided in project's documentation. MGSurvE is freely available as an open-source Python package on pypi ( https://pypi.org/project/MGSurvE/ ). It is intended as a resource for both field and computational researchers interested in mosquito gene surveillance. AUTHOR SUMMARY: Mosquito-borne diseases such as malaria and dengue fever continue to pose a major health burden throughout much of the world. The impact of currently-available tools, such as insecticides and antimalarial drugs, is stagnating, and gene drive-modified mosquitoes are considered a novel tool that could contribute to continuing reductions in disease transmission. Gene drive approaches are unique in the field of vector control in that they involve transgenes that could potentially spread on a wide scale, and consequently, surveillance is expected to be a major cost driver for the technology. This is needed to monitor for unintended spread of intact drive alleles, and the emergence of alternative alleles such as homing-resistance alleles and non-functional effector genes. Additionally, surveillance of insecticide-resistance alleles is of interest to support the impact of insecticide-based tools such as bednets. Here, we present MGSurvE, a computational framework that optimizes trap placement for genetic surveillance of mosquito populations in order to minimize the time to detection for an allele of interest. MGSurvE has been tailored to various features of mosquito ecology, and is intended as a resource for researchers to optimize the efficiency of limited surveillance resources.
Do sex-linked male meiotic drivers contribute to intrinsic hybrid incompatibilities? Recent empirical studies from flies and rodents
26254J. Kitano and K. Yoshida, Current Opinion in Genetics and Development, 81:102068. 2023-06-22 08:05:04.
Intrinsic hybrid incompatibility is one of the important isolating barriers between species. In organisms with sex chromosomes, intrinsic hybrid incompatibility often follows two rules: Haldane’s rule and large-X effects. One explanation for these two rules is that sex chromosomes are hotspots for meiotic drivers that can cause intrinsic hybrid incompatibility between geographically isolated populations. Although this hypothesis seems plausible and several empirical data are consistent with it, we are still unsure whether such mechanisms occur in nature, particularly with respect to speciation with gene flow. Here, we review empirical studies that have investigated the roles of meiotic drive in sex-chromosome evolution and speciation and propose future studies necessary for testing this hypothesis.
Developing methods for chilling, compacting, and sterilizing adult Aedes aegypti (Diptera: Culicidae) and comparing mating competitiveness between males sterilized as adults versus pupae for sterile male release
26602D. A. Tussey, R. Morreale, D. O. Carvalho, S. Stenhouse, A. M. Lloyd, D. F. Hoel and D. A. Hahn, Journal of Medical Entomology, 2023-06-21 13:03:55.
The yellow fever mosquito, Aedes aegypti L., can transmit several pathogens responsible for human diseases. With insecticide resistance development becoming a concern, alternative control strategies are needed for Ae. aegypti. Sterile insect technique (SIT) is an increasingly popular option being explored. However, logistical issues in mass production and sterilization make it difficult to maintain a SIT program. Male mosquitoes are typically irradiated as pupae because this is the earliest developmental point at which females can be separated from males, but asynchrony in pupation and high variability in pupal responses to irradiation based on pupal age make it difficult to sterilize mass quantities of pupae on a regular schedule in a rearing facility. Young adult mosquitoes have wider windows for irradiation sterilization than pupae, which can allow facilities to have fixed schedules for irradiation. We produced a workflow for adult Ae. aegypti irradiation in a mosquito control district with an operational SIT program that currently irradiates pupae. The impacts of chilling, compaction, and radiation dose on survival were all assessed before combining them into a complete adult irradiation protocol. Males chilled up to 16 h prior to compaction and compacted to 100 males/cm3 during radiation resulted in low mortality. Males irradiated as adults had increased longevity and similar sterility compared to males irradiated as pupae. Additionally, males sterilized as adults were more sexually competitive than males sterilized as pupae. Thus, we have shown that irradiating adult males can be a viable option to increase the efficiency of this operational mosquito SIT program.
Regulatory logic of endogenous RNAi in silencing de novo genomic conflicts
26252J. Vedanayagam, C. J. Lin, R. Papareddy, M. Nodine, A. S. Flynt, J. Wen and E. C. Lai, PLOS Genetics, 19:e1010787. 2023-06-21 07:57:17.
Although the biological utilities of endogenous RNAi (endo-RNAi) have been largely elusive, recent studies reveal its critical role in the non-model fruitfly Drosophila simulans to suppress selfish genes, whose unchecked activities can severely impair spermatogenesis. In particular, hairpin RNA (hpRNA) loci generate endo-siRNAs that suppress evolutionary novel, X-linked, meiotic drive loci. The consequences of deleting even a single hpRNA (Nmy) in males are profound, as such individuals are nearly incapable of siring male progeny. Here, comparative genomic analyses of D. simulans and D. melanogaster mutants of the core RNAi factor dcr-2 reveal a substantially expanded network of recently-emerged hpRNA-target interactions in the former species. The de novo hpRNA regulatory network in D. simulans provides insight into molecular strategies that underlie hpRNA emergence and their potential roles in sex chromosome conflict. In particular, our data support the existence of ongoing rapid evolution of Nmy/Dox-related networks, and recurrent targeting of testis HMG Box loci by hpRNAs. Importantly, the impact of the endo-RNAi network on gene expression flips the convention for regulatory networks, since we observe strong derepression of targets of the youngest hpRNAs, but only mild effects on the targets of the oldest hpRNAs. These data suggest that endo-RNAi are especially critical during incipient stages of intrinsic sex chromosome conflicts, and that continual cycles of distortion and resolution may contribute to speciation.
Effects of radiation on the fitness, sterility and arbovirus susceptibility of a Wolbachia-free Aedes albopictus strain for use in the Sterile Insect Technique
25867D. J. Zhang, S. Yan, H. Yamada, Y. Wu, G. Wang, Q. D. Feng, D. Paerhande, H. Maiga, J. Bouyer, J. Qian, Z. D. Wu and X. Y. Zheng, Pest Management Science, 2023-06-15 08:49:29.
BACKGROUND: The sterile insect technique (SIT) is a green and species-specific insect pest control technique that suppresses target populations by releasing factory-reared, radio-sterilized males into the wild. Once released, it is important to be able to distinguish the released males from the wild males for monitoring purposes. Several methods to mark the sterile males exist. However, most have limitations due to monetary, process efficiency, or insect quality. Aedes albopictus is naturally infected with Wolbachia at a high prevalence. Therefore, the elimination of Wolbachia can serve as a biomarker to distinguish the factory-reared male mosquitoes from wild conspecifics. RESULTS: In this study, a Wolbachia-free Ae. albopictus GT strain was developed and its fitness evaluated, which was found to be comparable to the wild GUA strain. In addition, GT male mosquitoes were irradiated at the adult stage and a dose of 20 Gy or more induced over 99% sterility. Moreover, a dose of 30 Gy (almost completely sterilizing male and female mosquitoes) had limited effects on the mating competitiveness of GT males and vector competence of GT females, respectively. However, radiation reduced mosquito longevity, regardless of its sex. CONCLUSION: Our results indicated that the Ae. albopictus GT strain can be distinguished from the wild mosquitoes based on Wolbachia status and shows similar fitness, radio-sensitivity and arbovirus susceptibility to the GUA strain, indicating that it is feasible to use the GT strain to suppress Ae. albopictus populations for SIT programmes. This article is protected by copyright. All rights reserved.
CRISPR-based gene drives generate super-Mendelian inheritance in the disease vector Culex quinquefasciatus
25865T. Harvey-Samuel, X. Feng, E. M. Okamoto, D.-K. Purusothaman, P. T. Leftwich, L. Alphey and V. M. Gantz, bioRxiv, 2023.06.12.544656. 2023-06-15 08:40:13.
Culex mosquitoes pose a significant public health threat as vectors for a variety of diseases including West Nile virus and lymphatic filariasis, and transmit pathogens threatening livestock, companion animals, and endangered birds. Rampant insecticide resistance makes controlling these mosquitoes challenging and necessitates the development of new control strategies. Gene drive technologies have made significant progress in other mosquito species, although similar advances have been lagging in Culex. Here we test the first CRISPR-based homing gene drive for Culex quinquefasciatus, demonstrating the possibility of using this technology to control Culex mosquitoes. Our results show that the inheritance of two split-gene-drive transgenes, targeting different loci, are biased in the presence of a Cas9-expressing transgene although with modest efficiencies. Our findings extend the list of disease vectors where engineered homing gene drives have been demonstrated to include Culex alongside Anopheles and Aedes, and pave the way for future development of these technologies to control Culex mosquitoes
CRISPR/Cas9-based split homing gene drive targeting doublesex for population suppression of the global fruit pest Drosophila suzukii
25710A. K. Yadav, C. Butler, A. Yamamoto, A. A. Patil, A. L. Lloyd and M. J. Scott, Proc Natl Acad Sci U S A, 120:e2301525120. 2023-06-13 10:38:33.
Genetic-based methods offer environmentally friendly species-specific approaches for control of insect pests. One method, CRISPR homing gene drive that target genes essential for development, could provide very efficient and cost-effective control. While significant progress has been made in developing homing gene drives for mosquito disease vectors, little progress has been made with agricultural insect pests. Here, we report the development and evaluation of split homing drives that target the doublesex (dsx) gene in Drosophila suzukii, an invasive pest of soft-skinned fruits. The drive component, consisting of dsx single guide RNA and DsRed genes, was introduced into the female-specific exon of dsx, which is essential for function in females but not males. However, in most strains, hemizygous females were sterile and produced the male dsx transcript. With a modified homing drive that included an optimal splice acceptor site, hemizygous females from each of the four independent lines were fertile. High transmission rates of the DsRed gene (94 to 99%) were observed with a line that expressed Cas9 with two nuclear localization sequences from the D. suzukii nanos promoter. Mutant alleles of dsx with small in-frame deletions near the Cas9 cut site were not functional and thus would not provide resistance to drive. Finally, mathematical modeling showed that the strains could be used for suppression of lab cage populations of D. suzukii with repeated releases at relatively low release ratios (1:4). Our results indicate that the split CRISPR homing gene drive strains could potentially provide an effective means for control of D. suzukii populations.
Sequence and expression analysis of the spermatogenesis-specific gene cognates, wampa and Prosα6T, in Drosophila suzukii
26182Q. Xia, K. Tariq, D. A. Hahn and A. M. Handler, Genetica, 2023-06-10 12:20:00.
The sterile insect technique (SIT) is a highly effective biologically-based method for the population suppression of highly invasive insect pests of medical and agricultural importance. The efficacy of SIT could be significantly enhanced, however, by improved methods of male sterilization that avoid the fitness costs of irradiation. An alternative sterilization method is possible by gene-editing that targets genes essential for sperm maturation and motility, rendering them nonfunctional, similar to the CRISPR-Cas9 targeting of β2-tubulin in the genetic model system, Drosophila melanogaster. However, since genetic strategies for sterility are susceptible to breakdown or resistance in mass-reared populations, alternative targets for sterility are important for redundancy or strain replacement. Here we have identified and characterized the sequence and transcriptional expression of two genes in a Florida strain of Drosophila suzukii, that are cognates of the D. melanogaster spermatocyte-specific genes wampa and Prosalpha6T. Wampa encodes a coiled-coil dynein subunit required for axonemal assembly, and the proteasome subunit gene, Prosalpha6T, is required for spermatid individualization and nuclear maturation. The reading frames of these genes differed from their NCBI database entries derived from a D. suzukii California strain by 44 and 8 nucleotide substitutions/polymorphisms, respectively, though all substitutions were synonymous resulting in identical peptide sequences. Expression of both genes is predominant in the male testis, and they share similar transcriptional profiles in adult males with β2-tubulin. Their amino acid sequences are highly conserved in dipteran species, including pest species subject to SIT control, supporting their potential use in targeted male sterilization strategies. © 2023, This is a U.S. Government work and not under copyright protection in the US; foreign copyright protection may apply.
The attitudes of young adults towards mammalian predator control and Predator Free 2050 in Aotearoa New Zealand
26186L. Dickie and F. Medvecky, Australasian Journal of Environmental Management, 2023-06-09 12:31:11.
Predator Free 2050 (PF2050) is an ambitious goal that aims to remove three types of invasive mammals from New Zealand by 2050. It will require a significant amount of funding, research, and support. Young adults will have an important role to play for this programme to be successful. Therefore, understanding the awareness and attitudes of young adults towards PF2050, and predator control, is an essential consideration. A survey of 1479 18- to 24-year-olds was conducted in 2017. The results showed that a higher percentage of young adults than members of the broader public view the small, introduced mammals as threats to New Zealand’s environment. Furthermore, this study highlights support for the control of feral, stray, and domestic cats. More focused research on attitudes towards cats is recommended to gauge which control methods are approved of by young adults. Indeed, methods appear to be a key factor to young adults supporting PF2050. The aerial distribution of poison was largely viewed negatively, and moderate concern was expressed about the targeted animal’s welfare. Interestingly, young adults appeared to be open to the use of gene editing and gene drive, although they expressed caution. Targeted communication towards young adults on toxins and genetic methods is recommended. © 2023 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.
Modeling emergence of Wolbachia toxin-antidote protein functions with an evolutionary algorithm
26277J. Beckmann, J. Gillespie and D. Tauritz, Front Microbiol, 14:1116766. 2023-06-09 10:36:38.
Evolutionary algorithms (EAs) simulate Darwinian evolution and adeptly mimic natural evolution. Most EA applications in biology encode high levels of abstraction in top-down population ecology models. In contrast, our research merges protein alignment algorithms from bioinformatics into codon based EAs that simulate molecular protein string evolution from the bottom up. We apply our EA to reconcile a problem in the field of Wolbachia induced cytoplasmic incompatibility (CI). Wolbachia is a microbial endosymbiont that lives inside insect cells. CI is conditional insect sterility that operates as a toxin antidote (TA) system. Although, CI exhibits complex phenotypes not fully explained under a single discrete model. We instantiate in-silico genes that control CI, CI factors (cifs), as strings within the EA chromosome. We monitor the evolution of their enzymatic activity, binding, and cellular localization by applying selective pressure on their primary amino acid strings. Our model helps rationalize why two distinct mechanisms of CI induction might coexist in nature. We find that nuclear localization signals (NLS) and Type IV secretion system signals (T4SS) are of low complexity and evolve fast, whereas binding interactions have intermediate complexity, and enzymatic activity is the most complex. Our model predicts that as ancestral TA systems evolve into eukaryotic CI systems, the placement of NLS or T4SS signals can stochastically vary, imparting effects that might impact CI induction mechanics. Our model highlights how preconditions and sequence length can bias evolution of cifs toward one mechanism or another.
How aggressive interactions with biomimetic agents optimize reproductive performances in mass-reared males of the Mediterranean fruit fly
25553D. Romano, G. Benelli and C. Stefanini, Biological Cybernetics, 2023-06-09 08:59:21.
Mass-rearing procedures of insect species, often used in biological control and Sterile Insect Technique, can reduce the insects competitiveness in foraging, dispersal, and mating. The evocation of certain behaviours responsible to induce specific neuroendocrine products may restore or improve the competitiveness of mass-reared individuals. Herein, we used a mass-reared strain of Ceratitis capitata as model organism. C. capitata is a polyphagous pest exhibiting territorial displays that are closely related to its reproductive performance. We tested if the behaviour of C. capitata males could be altered by hybrid aggressive interactions with a conspecific-mimicking robotic fly, leading to more competitive individuals in subsequent mating events. Aggressive interactions with the robotic fly had a notable effect on subsequent courtship and mating sequences of males that performed longer courtship displays compared to naïve individuals. Furthermore, previous interactions with the robotic fly produced a higher mating success of males. Reproductive performances of C. capitata males may be improved by specific octopaminergic neurones activated during previous aggressive interactions with the robotic fly. This study adds fundamental knowledge on the potential role of specific neuro-behavioural processes in the ecology of tephritid species and paves the way to innovative biotechnological control methods based on robotics and bionics.
Requirements for market entry of gene drive-modified mosquitoes for control of vector-borne diseases: analogies to other biologic and biotechnology products
26281S. L. James, H. Quemada, M. Q. Benedict and B. Dass, Frontiers in Bioengineering and Biotechnology, 11:1205865. 2023-06-08 10:56:02.
Gene drive-modified mosquitoes (GDMMs) are proposed as new tools for control and elimination of malaria and other mosquito-borne diseases, and promising results have been observed from testing conducted in containment. Although still at an early stage of development, it is important to begin now to consider approval procedures and market entry strategies for the eventual implementation of GDMMs in the context of disease control programs, as these could impact future research plans. It is expected that, as for other types of new products, those seeking to bring GDMMs to market will be required to provide sufficient information to allow the regulator(s) to determine whether the product is safe and effective for its proposed use. There already has been much emphasis on developing requirements for the biosafety components of the "safe and effective" benchmark, largely concerned with their regulation as genetically modified organisms. Other potential approval requirements have received little attention, however. Although GDMMs are expected to be implemented primarily in the context of public health programs, any regulatory analogies to other public health products, such as pharmaceuticals, vaccines, or chemical pesticides, must take into account the characteristics of live mosquito products. Typical manufacturing standards related to product identity, potency or quality will need to be adapted to GDMMs. Valuable lessons can be drawn from the regulatory approval processes for other whole organism and genetically modified (GM) organism products. Supply chain requirements, such as scale of production, location and design of production facilities, and methods of distribution and delivery, will be dependent upon the characteristics of the particular GDMM product, the conditions of use, and the region to be served. Plans for fulfilling supply chain needs can build upon experience in the development of other live insect products for use in public health and agriculture. Implementation of GDMMs would benefit from additional research on enabling technologies for long-term storage of mosquito life stages, efficient mass production, and area-wide delivery of GDMMs. Early consideration of these practical requirements for market entry will help to mitigate downstream delays in the development of these promising new technologies.
Essential and recurrent roles for hairpin RNAs in silencing de novo sex chromosome conflict in Drosophila simulans
25708J. Vedanayagam, M. Herbette, H. Mudgett, C. J. Lin, C. M. Lai, C. McDonough-Goldstein, S. Dorus, B. Loppin, C. Meiklejohn, R. Dubruille and E. C. Lai, PLoS Biol, 21:e3002136. 2023-06-08 10:27:14.
Meiotic drive loci distort the normally equal segregation of alleles, which benefits their own transmission even in the face of severe fitness costs to their host organism. However, relatively little is known about the molecular identity of meiotic drivers, their strategies of action, and mechanisms that can suppress their activity. Here, we present data from the fruitfly Drosophila simulans that address these questions. We show that a family of de novo, protamine-derived X-linked selfish genes (the Dox gene family) is silenced by a pair of newly emerged hairpin RNA (hpRNA) small interfering RNA (siRNA)-class loci, Nmy and Tmy. In the w[XD1] genetic background, knockout of nmy derepresses Dox and MDox in testes and depletes male progeny, whereas knockout of tmy causes misexpression of PDox genes and renders males sterile. Importantly, genetic interactions between nmy and tmy mutant alleles reveal that Tmy also specifically maintains male progeny for normal sex ratio. We show the Dox loci are functionally polymorphic within D. simulans, such that both nmy-associated sex ratio bias and tmy-associated sterility can be rescued by wild-type X chromosomes bearing natural deletions in different Dox family genes. Finally, using tagged transgenes of Dox and PDox2, we provide the first experimental evidence Dox family genes encode proteins that are strongly derepressed in cognate hpRNA mutants. Altogether, these studies support a model in which protamine-derived drivers and hpRNA suppressors drive repeated cycles of sex chromosome conflict and resolution that shape genome evolution and the genetic control of male gametogenesis.
Molecular detection of reproductive symbionts and parthenogenesis experiments in Tuta absoluta from Argentina: facing potential for sustainable and specific pest control strategies
26184C. Cagnotti, C. Conte, J. Kramar, S. Lanzavecchia and S. López, Entomologia Experimentalis et Applicata, 2023-06-07 12:24:43.
Tomato leafminer, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), is a key pest of tomato crops. Specific and environmentally friendly control strategies against this pest, such as the sterile insect technique (SIT), are under development and sexual reproduction has emerged as a key focal point to ensure its success. In the present study, we analyzed four representative T. absoluta populations from Argentina, focusing on the molecular detection of endosymbionts potentially associated with reproductive abnormalities and on determining whether parthenogenesis can occur under laboratory conditions. Larvae of T. absoluta were collected in commercial tomato plantations from La Plata and Mar del Plata (both in Buenos Aires province), Bella Vista (Corrientes province), and Yuto (Jujuy province). Tuta absoluta adults were evaluated by standard PCR for the presence of reproductive endosymbionts (Wolbachia sp., Spiroplasma sp., Arsenophonus sp., Cardinium sp., and Rickettsia sp.). For parthenogenesis assays, 20–23 virgin females from each T. absoluta geographic population were life-long isolated in Petri dishes with a tomato leaf. Fecundity, fertility, and female longevity were estimated and compared with results from mated females from each population. Our results showed the presence of a unique endosymbiont (Wolbachia sp. supergroup B, sequence type 41). Fecundity of the unmated females was significantly lower than fecundity of mated females in all T. absoluta populations. In addition, unmated females only laid infertile eggs. In conclusion, the absence of parthenogenesis in T. absoluta from representative geographic populations supports the implementation of SIT and mating disruption as effective control strategies against this pest in Argentina. © 2023 Netherlands Entomological Society.
Molecular Biology of Cytoplasmic Incompatibility Caused by Wolbachia Endosymbionts
25549M. Hochstrasser, Annual Review of Microbiology, 2023-06-07 08:38:45.
Among endosymbiotic bacteria living within eukaryotic cells, Wolbachia is exceptionally widespread, particularly in arthropods. Inherited through the female germline, it has evolved ways to increase the fraction of bacterially infected offspring by inducing parthenogenesis, feminization, male killing, or, most commonly, cytoplasmic incompatibility (CI). In CI, Wolbachia infection of males causes embryonic lethality unless they mate with similarly infected females, creating a relative reproductive advantage for infected females. A set of related Wolbachia bicistronic operons encodes the CI-inducing factors. The downstream gene encodes a deubiquitylase or nuclease and is responsible for CI induction by males, while the upstream product when expressed in females binds its sperm-introduced cognate partner and rescues viability. Both toxin-antidote and host-modification mechanisms have been proposed to explain CI. Interestingly, male killing by either Spiroplasma or Wolbachia endosymbionts involves deubiquitylases as well. Interference with the host ubiquitin system may therefore be a common theme among endosymbiont-mediated reproductive alterations.
Cell biology: Selfish B chromosomes unleashed by a dysfunctional chromosome segregation system
25563P. Ferree, Current Biology, 33:R431-R434. 2023-06-05 09:18:59.
A study in the fruit fly Drosophila melanogaster shows that a defective chromosome segregation system allows non-essential B chromosomes to transmit at higher-than-Mendelian frequencies.
Wolbachia -induced inhibition of O’nyong nyong virus in Anopheles mosquitoes is mediated by Toll signaling and modulated by cholesterol
26465S. Pujhari, G. L. Hughes, N. Pakpour, Y. Suzuki and J. L. Rasgon, bioRxiv, 10.1101/2023.05.31.543096. 2023-06-01 07:41:43.
Enhanced host immunity and competition for metabolic resources are two main competing hypotheses for the mechanism of Wolbachia -mediated pathogen inhibition in arthropods. Using an Anopheles mosquito - somatic Wolbachia infection - O'nyong nyong virus (ONNV) model, we demonstrate that the mechanism underpinning Wolbachia -mediated virus inhibition is up-regulation of the Toll innate immune pathway. However, the viral inhibitory properties of Wolbachia were abolished by cholesterol supplementation. This result was due to Wolbachia -dependent cholesterol-mediated suppression of Toll signaling rather than competition for cholesterol between Wolbachia and virus. The inhibitory effect of cholesterol was specific to Wolbachia -infected Anopheles mosquitoes and cells. These data indicate that both Wolbachia and cholesterol influence Toll immune signaling in Anopheles mosquitoes in a complex manner and provide a functional link between the host immunity and metabolic competition hypotheses for explaining Wolbachia -mediated pathogen interference in mosquitoes. In addition, these results provide a mechanistic understanding of the mode of action of Wolbachia -induced pathogen blocking in Anophelines, which is critical to evaluate the long-term efficacy of control strategies for malaria and Anopheles -transmitted arboviruses. HIGHLIGHTS: Wolbachia inhibits O'nyong nyong virus (ONNV) in Anopheles mosquitoes. Enhanced Toll signaling is responsible for Wolbachia -induced interference of ONNV. Cholesterol suppresses Toll signaling to modulate Wolbachia -induced ONNV interference.
A framework for identifying fertility gene targets for mammalian pest control
25416C. C. Anna, A. Alana, E. Rey, E. Kevin, K. Sebastian, D. Ludovic, C. Jackson, E. C. Samuel, W. M. Philipp and J. G. Neil, bioRxiv, 2023.05.30.542751. 2023-06-01 07:38:46.
Fertility-targeted gene drives have been proposed as an ethical genetic approach for managing wild populations of vertebrate pests for public health and conservation benefit. This manuscript introduces a framework to identify and evaluate target gene suitability based on biological gene function, gene expression, and results from mouse knockout models. This framework identified 16 genes essential for male fertility and 12 genes important for female fertility that may be feasible targets for mammalian gene drives and other non-drive genetic pest control technology. Further, a comparative genomics analysis demonstrates the conservation of the identified genes across several globally significant invasive mammals. In addition to providing important considerations for identifying candidate genes, our framework and the genes identified in this study may have utility in developing additional pest control tools such as wildlife contraceptives.Competing Interest StatementThe authors have declared no competing interest.
An economic evaluation of Wolbachia deployments for dengue control in Vietnam
25418H. C. Turner, D. L. Quyen, R. Dias, P. T. Huong, C. P. Simmons and K. L. Anders, PLOS Neglected Tropical Diseases, 17:e0011356. 2023-05-30 07:56:11.
INTRODUCTION: Dengue is a major public health challenge and a growing problem due to climate change. The release of Aedes aegypti mosquitoes infected with the intracellular bacterium Wolbachia is a novel form of vector control against dengue. However, there remains a need to evaluate the benefits of such an intervention at a large scale. In this paper, we evaluate the potential economic impact and cost-effectiveness of scaled Wolbachia deployments as a form of dengue control in Vietnam-targeted at the highest burden urban areas. METHODS: Ten settings within Vietnam were identified as priority locations for potential future Wolbachia deployments (using a population replacement strategy). The effectiveness of Wolbachia deployments in reducing the incidence of symptomatic dengue cases was assumed to be 75%. We assumed that the intervention would maintain this effectiveness for at least 20 years (but tested this assumption in the sensitivity analysis). A cost-utility analysis and cost-benefit analysis were conducted. RESULTS: From the health sector perspective, the Wolbachia intervention was projected to cost US$420 per disability-adjusted life year (DALY) averted. From the societal perspective, the overall cost-effectiveness ratio was negative, i.e. the economic benefits outweighed the costs. These results are contingent on the long-term effectiveness of Wolbachia releases being sustained for 20 years. However, the intervention was still classed as cost-effective across the majority of the settings when assuming only 10 years of benefits. CONCLUSION: Overall, we found that targeting high burden cities with Wolbachia deployments would be a cost-effective intervention in Vietnam and generate notable broader benefits besides health gains.
The optimal strategy of incompatible insect technique (IIT) using Wolbachia and the application to malaria control
25203T. Matsufuji and S. Seirin-Lee, Journal of Theoretical Biology, 569:111519. 2023-05-29 09:18:33.
For decades, techniques to control vector population with low environmental impact have been widely explored in both field and theoretical studies. The incompatible insect technique (IIT) using Wolbachia, based on cytoplasmic incompatibility, is a technique that Wolbachia-infected male mosquitoes are incapable of producing viable offspring after mating with wild-type female mosquitoes. While the IIT method experimentally ensured its effectiveness in several field works, the failure of female mosquito population control by replacement owing to the accidental contamination of Wolbachia-infected female mosquitoes has been a concern and an obstacle in implementing the IIT method in nature. In this study, we develop a population-based IIT mathematical model using cytoplasmic incompatibility and evaluate the effectiveness of the IIT method in scenarios where contamination is present or absent. In addition, by extending the model to assess the disease infection status of the human population with malaria, we evaluate the optimal release strategy and cost for successful disease control. Our study proves that IIT could be a promising method to control mosquito-borne diseases without perfect suppression of vector mosquito population regardless of contamination.
The prevalence of Wolbachia in multiple cockroach species and its implication for urban insect management
25869S. O. Oladipupo, Y. Laidoudi, J. F. Beckmann, X. P. Hu and A. G. Appel, Journal of Economic Entomology, 2023-05-29 08:56:29.
Cockroach management relies heavily on the use of conventional insecticides in urban settings, which no longer provide the anticipated level of control. Knowledge of cockroach endosymbionts, like Wolbachia, might provide novel avenues for control. Therefore, we screened 16 cockroach species belonging to 3 families (Ectobiidae, Blattidae, and Blaberidae) for the presence of Wolbachia. We mapped the evolution of Wolbachia-cockroach relationships based on maximum likelihood phylogeny and phylogenetic species clustering on a multi-loci sequence dataset (i.e., coxA, virD4, hcpA, and gatB) of Wolbachia genes. We confirmed the previous report of Wolbachia in 1 Ectobiid species; Supella longipalpa (Fab.), and detected the presence of Wolbachia in 2 Ectobiid species; Balta notulata (Stål) and Pseudomops septentrionalis Hebard, and 1 Blaberid species; Gromphadorhina portentosa (Schaum). All cockroach-associated Wolbachia herein detected were clustered with the ancestor of F clade Wolbachia of Cimex lectularius L. (bed bugs). Since Wolbachia provision C. lectularius with biotin vitamins that confer reproductive fitness, we screened the cockroach-associated Wolbachia for the presence of biotin genes. In toto, our results reveal 2 important findings: (i) Wolbachia is relatively uncommon among cockroach species infecting about 25% of species investigated, and (ii) cockroach-associated Wolbachia have biotin genes that likely provide nutritional benefits to their hosts. Thus, we discuss the potential of exploring Wolbachia as a tool for urban insect management.
CRISPR-based gene editing of non-homologous end joining factors biases DNA repair pathway choice toward single-strand annealing in Aedes aegypti
25461K. Chae, J. M. Overcash, C. Dawson, C. Valentin, H. Tsujimoto, K. M. Myles and Z. N. Adelman, Current Research in Biotechnology, 5:100133. 2023-05-29 08:04:22.
To maintain genome stability, eukaryotic cells orchestrate DNA repair pathways to process DNA double-strand breaks (DSBs) that result from diverse developmental or environmental stimuli. Bias in the selection of DSB repair pathways, either non-homologous end joining (NHEJ) or homology-directed repair (HDR), is also critical for efficient gene editing and for homing-based gene drive approaches developed for the control of disease-transmitting vector mosquitoes. However, little is understood about DNA repair homeostasis in the mosquito genome. Here, we utilized CRISPR/Cas9 to generate indel mutant strains for core NHEJ factors ku80, DNA ligase IV (lig4), and DNA-PKcs in the mosquito Aedes aegypti and evaluated the corresponding effects on DNA repair. In a plasmid-based assay, disruption of ku80 or lig4, but not DNA-PKcs, reduced both NHEJ and SSA. However, a transgenic reporter strain-based test revealed that those mutations significantly biased DNA repair events toward SSA. Interestingly, ku80 mutation also significantly increased the end joining rate by a yet-characterized mechanism in males. Our study provides evidence that the core NHEJ factors have an antagonistic effect on SSA-based DSB repair of the Ae. aegypti genome. Down-modulating the NHEJ pathway can enhance the efficiency of nuclease-based genetic control approaches, as most of those operate by homology-based repair processes along with extensive DNA end resection that is antagonized by NHEJ.
Wolbachia protects Drosophila melanogaster against two naturally occurring and virulent viral pathogens
25211G. Bruner-Montero and F. M. Jiggins, Scientific Reports, 13:8518. 2023-05-25 13:38:46.
Wolbachia is a common endosymbiont that can protect insects against viral pathogens. However, whether the antiviral effects of Wolbachia have a significant effect on fitness remains unclear. We have investigated the interaction between Drosophila melanogaster, Wolbachia and two viruses that we recently isolated from wild flies, La Jolla virus (LJV; Iflaviridae) and Newfield virus (NFV; Permutotetraviridae). Flies infected with these viruses have increased mortality rates, and NFV partially sterilizes females. These effects on fitness were reduced in Wolbachia-infected flies, and this was associated with reduced viral titres. However, Wolbachia alone also reduces survival, and under our experimental conditions these costs of the symbiont can outweigh the benefits of antiviral protection. In contrast, protection against the sterilizing effect of NFV leads to a net benefit of Wolbachia infection after exposure to the virus. These results support the hypothesis that Wolbachia is an important defense against the natural pathogens of D. melanogaster. Furthermore, by reducing the cost of Wolbachia infection, the antiviral effects of Wolbachia may aid its invasion into populations and help explain why it is so common in nature.
Holobiont perspectives on tripartite interactions among microbiota, mosquitoes, and pathogens
25208R. Zheng, Q. Wang, R. Wu, P. N. Paradkar, A. A. Hoffmann and G. H. Wang, ISME, 2023-05-25 13:32:28.
Mosquito-borne diseases like dengue and malaria cause a significant global health burden. Unfortunately, current insecticides and environmental control strategies aimed at the vectors of these diseases are only moderately effective in decreasing disease burden. Understanding and manipulating the interaction between the mosquito holobiont (i.e., mosquitoes and their resident microbiota) and the pathogens transmitted by these mosquitoes to humans and animals could help in developing new disease control strategies. Different microorganisms found in the mosquito's microbiota affect traits related to mosquito survival, development, and reproduction. Here, we review the physiological effects of essential microbes on their mosquito hosts; the interactions between the mosquito holobiont and mosquito-borne pathogen (MBP) infections, including microbiota-induced host immune activation and Wolbachia-mediated pathogen blocking (PB); and the effects of environmental factors and host regulation on the composition of the microbiota. Finally, we briefly overview future directions in holobiont studies, and how these may lead to new effective control strategies against mosquitoes and their transmitted diseases.
Wolbachia genetically interacts with the bag of marbles germline stem cell gene in male D. melanogaster
26548M. Wenzel and C. F. Aquadro, MicroPubl Biol, 2023-05-25 08:57:31.
The bacterial endosymbiont Wolbachia manipulates reproduction of its arthropod hosts to promote its own maternal vertical transmission. In female D. melanogaster , Wolbachia has been shown to genetically interact with three key reproductive genes ( bag of marbles ( bam ) , Sex-lethal, and mei-P26) , as it rescues the reduced female fertility or fecundity phenotype seen in partial loss-of-function mutants of these genes . Here, we show that Wolbachia also partially rescues male fertility in D. melanogaster carrying a new, largely sterile bam allele when in a bam null genetic background. This finding shows that the molecular mechanism of Wolbachia 's influence on its hosts' reproduction involves interaction with genes in males as well as females, at least in D. melanogaster .
Mosquito gene targeted RNAi studies for vector control
25650M. Yadav, N. Dahiya and N. Sehrawat, Functional and Integrative Genomics, 23:180. 2023-05-25 07:55:21.
Vector-borne diseases are serious public health concern. Mosquito is one of the major vectors responsible for the transmission of a number of diseases like malaria, Zika, chikungunya, dengue, West Nile fever, Japanese encephalitis, St. Louis encephalitis, and yellow fever. Various strategies have been used for mosquito control, but the breeding potential of mosquitoes is such tremendous that most of the strategies failed to control the mosquito population. In 2020, outbreaks of dengue, yellow fever, and Japanese encephalitis have occurred worldwide. Continuous insecticide use resulted in strong resistance and disturbed the ecosystem. RNA interference is one of the strategies opted for mosquito control. There are a number of mosquito genes whose inhibition affected mosquito survival and reproduction. Such kind of genes could be used as bioinsecticides for vector control without disturbing the natural ecosystem. Several studies have targeted mosquito genes at different developmental stages by the RNAi mechanism and result in vector control. In the present review, we included RNAi studies conducted for vector control by targeting mosquito genes at different developmental stages using different delivery methods. The review could help the researcher to find out novel genes of mosquitoes for vector control.
Adaptation in the face of internal conflict: the paradox of the organism revisited
25238M. M. Patten, M. A. Schenkel and J. A. Ågren, Biological Reviews, 2023-05-19 07:37:20.
The paradox of the organism refers to the observation that organisms appear to function as coherent purposeful entities, despite the potential for within-organismal components like selfish genetic elements and cancer cells to erode them from within. While it is commonly accepted that organisms may pursue fitness maximisation and can be thought to hold particular agendas, there is a growing recognition that genes and cells do so as well. This can lead to evolutionary conflicts between an organism and the parts that reside within it. Here, we revisit the paradox of the organism. We first outline its conception and relationship to debates about adaptation in evolutionary biology. Second, we review the ways selfish elements may exploit organisms, and the extent to which this threatens organismal integrity. To this end, we introduce a novel classification scheme that distinguishes between selfish elements that seek to distort transmission versus those that seek to distort phenotypic traits. Our classification scheme also highlights how some selfish elements elude a multi-level selection decomposition using the Price equation. Third, we discuss how the organism can retain its status as the primary fitness-maximising agent in the face of selfish elements. The success of selfish elements is often constrained by their strategy and further limited by a combination of fitness alignment and enforcement mechanisms controlled by the organism. Finally, we argue for the need for quantitative measures of both internal conflicts and organismality.
Near-infrared imaging for automated tsetse pupae sex sorting in support of the sterile insect technique
25472R. Argilés-Herrero, G. Salvador-Herranz, A. G. Parker, M. Zacarés, A. G. Fall, A. M. Gaye, A. Nawaz, P. Takáč, M. J. B. Vreysen and C. J. de Beer, Parasite, 30. 2023-05-17 08:49:45.
Tsetse flies are the cyclical vectors of African trypanosomes and one of several methods to manage this vector is the sterile insect technique (SIT). The ability to determine the sex of tsetse pupae with the objective to separate the sexes before adult emergence has been a major goal for decades for tsetse management programmes with an SIT component. Tsetse females develop faster and pharate females inside the pupae melanise 1–2 days before males. This earlier melanisation can be detected by infrared cameras through the pupal shell, and the newly developed Near InfraRed Pupae Sex Sorter (NIRPSS) takes advantage of this. The melanisation process is not homogeneous for all fly organs and the pupa needs to be examined ventrally, dorsally and laterally to ensure accurate classification by an image analysis algorithm. When the pupae are maturing at a constant temperature of 24 °C and sorted at the appropriate age, 24 days post-larviposition for Glossina palpalis gambiensis, the sorting machine can efficiently separate the sexes. The recovered male pupae can then be sterilised for field releases of males, while the rest of the pupae can be used to maintain the laboratory colony. The sorting process with the new NIRPSS had no negative impact on adult emergence and flight ability. A mean male recovery of 62.82 ± 3.61% was enough to provide sterile males to an operational SIT programme, while mean contamination with females (4.69 ± 3.02%) was low enough to have no impact on the maintenance of a laboratory colony
Transinfected Wolbachia strains induce a complex of cytoplasmic incompatibility phenotypes: Roles of CI factor genes
J. Li, B. Dong, Y. Zhong and Z. X. Li, Environmental Microbiology, 2023-05-16 08:29:22.Wolbachia can modulate the reproductive development of their hosts in multiple modes, and cytoplasmic incompatibility (CI) is the most well-studied phenotype. The whitefly Bemisia tabaci is highly receptive to different Wolbachia strains: wCcep strain from the rice moth Corcyra cephalonica and wMel strain from the fruit fly Drosophila melanogaster could successfully establish and induce CI in transinfected whiteflies. Nevertheless, it is unknown what will happen when these two exogenous Wolbachia strains are co-transinfected into a new host. Here, we artificially transinferred wCcep and wMel into the whitefly and established double- and singly-transinfected B. tabaci isofemale lines. Reciprocal crossing experiments showed that wCcep and wMel induced a complex of CI phenotypes in the recipient host, including unidirectional and bidirectional CI. We next sequenced the whole genome of wCcep and performed a comparative analysis of the CI factor genes between wCcep and wMel, indicating that their cif genes were phylogenetically and structurally divergent, which can explain the crossing results. The amino acid sequence identity and structural features of Cif proteins may be useful parameters for predicting their function. Structural comparisons between CifA and CifB provide valuable clues for explaining the induction or rescue of CI observed in crossing experiments between transinfected hosts.
Leveraging eco-evolutionary models for gene drive risk assessment
25157M. A. Combs, A. J. Golnar, J. M. Overcash, A. L. Lloyd, K. R. Hayes, D. A. O’Brochta and K. M. Pepin, Trends in Genetics, 2023-05-15 15:09:00.
As development of gene drive systems accelerates and diversifies, predicting outcomes for target populations and the potential for human and environmental risks requires accounting for numerous eco-evolutionary processes.Gene drive dynamic models quantify the influence of features across genetics (e.g., resistance development and standing genetic diversity), demographics (e.g., mating systems and inbreeding), spatial ecology (e.g., dispersal and competition), biotic and abiotic environments (e.g., climate variation and landscape structure), and implementation strategies (e.g., introduction size and timing) on gene drive outcomes.Synthesizing published gene drive models reveals research trends, knowledge gaps, and emergent principles. Modeling limitations and tradeoffs are discussed.Integrating an iterative modeling approach within the existing phased pathway for gene drive research improves utility for risk assessment.
Rapid, scalable, combinatorial genome engineering by marker-less enrichment and recombination of genetically engineered loci in yeast
26189M. Abdullah, B. M. Greco, J. M. Laurent, R. K. Garge, D. R. Boutz, M. Vandeloo, E. M. Marcotte and A. H. Kachroo, Cell Rep Methods, 3:100464. 2023-05-10 12:35:58.
A major challenge to rationally building multi-gene processes in yeast arises due to the combinatorics of combining all of the individual edits into the same strain. Here, we present a precise and multi-site genome editing approach that combines all edits without selection markers using CRISPR-Cas9. We demonstrate a highly efficient gene drive that selectively eliminates specific loci by integrating CRISPR-Cas9-mediated double-strand break (DSB) generation and homology-directed recombination with yeast sexual assortment. The method enables marker-less enrichment and recombination of genetically engineered loci (MERGE). We show that MERGE converts single heterologous loci to homozygous loci at ∼100% efficiency, independent of chromosomal location. Furthermore, MERGE is equally efficient at converting and combining multiple loci, thus identifying compatible genotypes. Finally, we establish MERGE proficiency by engineering a fungal carotenoid biosynthesis pathway and most of the human α-proteasome core into yeast. Therefore, MERGE lays the foundation for scalable, combinatorial genome editing in yeast.
Combined actions of bacteriophage-encoded genes in Wolbachia-induced male lethality
25420H. Arai, H. Anbutsu, Y. Nishikawa, M. Kogawa, K. Ishii, M. Hosokawa, S. R. Lin, M. Ueda, M. Nakai, Y. Kunimi, T. Harumoto, D. Kageyama, H. Takeyama and M. N. Inoue, iScience, 26:106842. 2023-05-10 08:02:36.
Some Wolbachia endosymbionts induce male killing, whereby male offspring of infected females are killed during development; however, the origin and diversity of the underlying mechanisms remain unclear. In this study, we identified a 76 kbp prophage region specific to male-killing Wolbachia hosted by the moth Homona magnanima. The prophage encoded a homolog of the male-killing gene oscar in Ostrinia moths and the wmk gene that induces various toxicities in Drosophila melanogaster. Upon overexpressing these genes in D. melanogaster, wmk-1 and wmk-3 killed all males and most females, whereas Hm-oscar, wmk-2, and wmk-4 had no impact on insect survival. Strikingly, co-expression of tandemly arrayed wmk-3 and wmk-4 killed 90% of males and restored 70% of females, suggesting their conjugated functions for male-specific lethality. While the male-killing gene in the native host remains unknown, our findings highlight the role of bacteriophages in male-killing evolution and differences in male-killing mechanisms among insects.
Editorial: Genetic control of insect pest species—achievements, challenges, and perspectives
25423I. Häcker, D. Bartsch, A. Choo and F. Marec, Frontiers in Bioengineering and Biotechnology, 11. 2023-05-05 08:12:07.
Genetic control is a type ofbiological control and a promising approach to regulate insect pest populations in a species-specific manner. It is based on targeting the reproductive capacity of the target pest species to reduce population size to non-critical levels. The best known and also very successful genetic control strategy is the Sterile Insect Technique (SIT), which entails the continuous mass-release ofirradiation-sterilized males ofa given species to produce infertile matings in the field, leading to the decline in the target population over time. To date, SIT is only available for a few species, as its transfer to new target species is challenging and time consuming. Key aspects of this classical SIT and challenges in applying it to new pest species include mass rearing of target species, mass removal of female insects prior to irradiation and release, the sterilization procedure, and the biological quality control of the sterile insects produced. Besides this classical SIT strategy, current research efforts are also focused on the development of genetic control approaches based on transgenic, symbiont-mediated, or gene-drive strategies. Modern genetic technologies offer new solutions for the improvement of existing genetic control strategies and insect strains, for faster and easier transfer of existing strategies to new target species, and also for the development of new genetic control approaches. Publications within this Research Topic address pressing questions and challenges related to the genetic control of insect pests.
The boundary problem: Defining and delineating the community in field trials with gene drive organisms
25098N. de Graeff, I. Pirson, R. van der Graaf, A. L. Bredenoord and K. R. Jongsma, Bioethics, 2023-05-03 10:11:03.
Despite widespread and worldwide efforts to eradicate vector-borne diseases such as malaria, these diseases continue to have an enormous negative impact on public health. For this reason, scientists are working on novel control strategies, such as gene drive technologies (GDTs). As GDT research advances, researchers are contemplating the potential next step of conducting field trials. An important point of discussion regarding these field trials relates to who should be informed, consulted, and involved in decision-making about their design and launch. It is generally argued that community members have a particularly strong claim to be engaged, and yet, disagreement and lack of clarity exist about how this "community" should be defined and delineated. In this paper, we shed light on this "boundary problem": the problem of determining how boundaries of inclusion and exclusion in (GDT) community engagement should be drawn. As our analysis demonstrates, the process of defining and delineating a community is itself normative. First, we explicate why it is important to define and delineate the community. Second, we demonstrate that different definitions of community are used and intermingled in the debate on GDTs, and argue in favor of distinguishing geographical, affected, cultural, and political communities. Finally, we propose initial guidance for deciding who should (not) be engaged in decision-making about GDT field trials, by arguing that the definition and delineation of the community should depend on the rationale for engagement and that the characteristics of the community itself can guide the effective design of community engagement strategies.
Mathematical modeling of the performance of wild and transgenic mosquitoes in malaria transmission
25861A. P. Wyse, A. J. B. dos Santos, J. D. Azevedo, A. C. de Meneses and V. M. D. Santos, Plos One, 18:23. 2023-04-28 08:20:19.
A mathematical model that simulates malaria transmission under the influence of transgenic mosquitoes refractory to malaria is presented in this paper. The zygosity of transgenic mosquitoes is taken into account and, consequently, the total population of mosquitoes is comprised of wild type and heterozygous and homozygous transgenic mosquitoes. These three mosquito varieties interact by mating and competition, and the genetic characteristics of their resulting offspring are in accordance with Mendelian genetics or the mutagenic chain reaction (MCR) technique. Although the incorporation of transgenic mosquitoes into the ecosystem reduces the incidence of malaria, the model also takes into account the importance of completing treatment in individuals with confirmed infection and the imminent risk of increased environmental temperature.
B chromosomes reveal a female meiotic drive suppression system in Drosophila melanogaster
25112S. L. Hanlon and R. S. Hawley, Current Biology, 2023-04-27 10:03:45.
Selfish genetic elements use a myriad of mechanisms to drive their inheritance and ensure their survival into the next generation, often at a fitness cost to its host.(1)(,)(2) Although the catalog of selfish genetic elements is rapidly growing, our understanding of host drive suppression systems that counteract self-seeking behavior is lacking. Here, we demonstrate that the biased transmission of the non-essential, non-driving B chromosomes in Drosophila melanogaster can be achieved in a specific genetic background. Combining a null mutant of matrimony, a gene that encodes a female-specific meiotic regulator of Polo kinase,(3)(,)(4) with the TM3 balancer chromosome creates a driving genotype that is permissive for the biased transmission of the B chromosomes. This drive is female-specific, and both genetic components are necessary, but not individually sufficient, for permitting a strong drive of the B chromosomes. Examination of metaphase I oocytes reveals that B chromosome localization within the DNA mass is mostly abnormal when drive is the strongest, indicating a failure of the mechanism(s) responsible for the proper distribution of B chromosomes. We propose that some proteins important for proper chromosome segregation during meiosis, like Matrimony, may have an essential role as part of a meiotic drive suppression system that modulates chromosome segregation to prevent genetic elements from exploiting the inherent asymmetry of female meiosis.
Wolbachia-based strategies for control of agricultural pests
25104J. T. Gong, T. P. Li, M. K. Wang and X. Y. Hong, Curr Opin Insect Sci, 101039:10.1016/j.cois.2023.101039. 2023-04-25 10:26:15.
Wolbachia-based incompatible insect technique (IIT) and pathogen blocking technique (PBT) have been shown to be effective at protecting humans from mosquito-borne diseases in the past decades. Population suppression based on IIT and population replacement based on PBT have become major field application strategies that have continuously been improved by the translational research on Wolbachia-transinfected mosquitoes. Similarly, Wolbachia-based approaches have been proposed for the protection of plants from agricultural pests and their associated diseases. However, a bottleneck in Wolbachia-based strategies for the control of agricultural pests is the need for methods to establish Wolbachia-transinfected insect lines. As a first step in this direction, we compare field control strategies for mosquitos with the potential strategies for agricultural pests based on Wolbachia. Our results show that there is a critical need for establishing productive insect lines and accumulating field test data.
Anti-CRISPR Anopheles mosquitoes inhibit gene drive spread under challenging behavioural conditions in large cages
25086A. Simoni, R. D'Amato, C. Taxiarchi, M. Galardini, A. Trusso, R. Minuz, S. Gilli, A. Somerville, D. Shittu, A. Khalil, R. Galizi and R. Muller, Research Square, 2023-04-24 06:46:30.
CRISPR-based gene drives have the potential to spread within a population and are considered as promising vector control tools. A doublesex-targeting gene drive was shown effective to suppress laboratory populations in both small and large cages, and it is considered for field application. Challenges related to the field-use of gene drives and the evolving regulatory framework demand for systems able to modulate or revert the action of gene drives, as part of post-release risk-mitigation plans. We developed an improved AcrIIA4-based anti-drive strain and showed inhibition of gene drive spread, in complex feeding and reproductive behavioural conditions. A stochastic model predicted the experimentally-observed genotypes dynamics in overlapping generations in medium- and large-sized cages and further demonstrated the effectiveness of anti-drive in different release and fitness scenarios. This study provides a further validation for the use of anti-drive system in controlling the spread of gene drive in Anopheles under complex behavioural conditions.
Applications of Anti-CRISPR Proteins in Genome Editing and Biotechnology
C. Kraus and E. J. Sontheimer, Journal of Molecular Biology, 2023-04-24 06:39:49.In the ten years since the discovery of the first anti-CRISPR (Acr) proteins, the number of validated Acrs has expanded rapidly, as has our understanding of the diverse mechanisms they employ to suppress natural CRISPR-Cas immunity. Many, though not all, function via direct, specific interaction with Cas protein effectors. The abilities of Acr proteins to modulate the activities and properties of CRISPR-Cas effectors have been exploited for an ever-increasing spectrum of biotechnological uses, most of which involve the establishment of control over genome editing systems. This control can be used to minimize off-target editing, restrict editing based on spatial, temporal, or conditional cues, limit the spread of gene drive systems, and select for genome-edited bacteriophages. Anti-CRISPRs have also been developed to overcome bacterial immunity, facilitate viral vector production, control synthetic gene circuits, and other purposes. The impressive and ever-growing diversity of Acr inhibitory mechanisms will continue to allow the tailored applications of Acrs.
A rapidly spreading deleterious aphid endosymbiont that uses horizontal as well as vertical transmission
25082X. Gu, P. A. Ross, A. Gill, Q. Yang, E. Ansermin, S. Sharma, S. Soleimannejad, K. Sharma, A. Callahan, C. Brown, P. A. Umina, T. N. Kristensen and A. A. Hoffmann, Proceedings of the National Academy of Sciences, 120:e2217278120. 2023-04-24 06:34:04.
Endosymbiotic bacteria that live inside the cells of insects are typically only transmitted maternally and can spread by increasing host fitness and/or modifying reproduction in sexual hosts. Transinfections of Wolbachia endosymbionts are now being used to introduce useful phenotypes into sexual host populations, but there has been limited progress on applications using other endosymbionts and in asexual populations. Here, we develop a unique pathway to application in aphids by transferring the endosymbiont Rickettsiella viridis to the major crop pest Myzus persicae. Rickettsiella infection greatly reduced aphid fecundity, decreased heat tolerance, and modified aphid body color, from light to dark green. Despite inducing host fitness costs, Rickettsiella spread rapidly through caged aphid populations via plant-mediated horizontal transmission. The phenotypic effects of Rickettsiella were sensitive to temperature, with spread only occurring at 19 °C and not 25 °C. Body color modification was also lost at high temperatures despite Rickettsiella maintaining a high density. Rickettsiella shows the potential to spread through natural M. persicae populations by horizontal transmission and subsequent vertical transmission. Establishment of Rickettsiella in natural populations could reduce crop damage by modifying population age structure, reducing population growth and providing context-dependent effects on host fitness. Our results highlight the importance of plant-mediated horizontal transmission and interactions with temperature as drivers of endosymbiont spread in asexual insect populations.
