For Researchers
Maxizyme-mediated suppression of chikungunya virus replication and transmission in transgenic Aedes aegypti mosquitoes
28819Mishra P, Balaraman V, Fraser Jr. M, Frontiers in Microbiology, 14. 2024-01-23 14:40:52.
Chikungunya virus (CHIKV) is an emerging mosquito-borne pathogen of significant public health importance. There are currently no prophylactic vaccines or therapeutics available to control CHIKV. One approach to arbovirus control that has been proposed is the replacement of transmission-competent mosquitoes with those that are refractory to virus infection. Several transgene effectors are being examined as potentially useful for this population replacement approach. We previously demonstrated the successful use of hammerhead ribozymes (hRzs) as an antiviral effector transgene to control CHIKV infection of, and transmission by, Aedes mosquitoes. In this report we examine a maxizyme approach to enhance the catalytic activity and prevent virus mutants from escaping these ribozymes. We designed a maxizyme containing minimized (monomer) versions of two hRzs we previously demonstrated to be the most effective in CHIKV suppression. Three versions of CHIKV maxizyme were designed: Active (Mz), inactive (ΔMz), and a connected CHIKV maxizyme (cMz). The maxizymes with their expression units (Ae-tRNA val promoter and its termination signal) were incorporated into lentivirus vectors with selection and visualization markers. Following transformation, selection, and single-cell sorting of Vero cells, clonal cell populations were infected with CHIKV at 0.05 and 0.5 MOI, and virus suppression was assessed using TCID50-IFA, RT-qPCR, and caspase-3 assays. Five transgenic mosquito lines expressing cMz were generated and transgene insertion sites were confirmed by splinkerette PCR. Our results demonstrate that Vero cell clones expressing Mz exhibited complete inhibition of CHIKV replication compared to their respective inactive control version or the two parent hRzs. Upon oral challenge of transgenic mosquitoes with CHIKV, three out of the five lines were completely refractory to CHIKV infection, and all five lines tested negative for salivary transmission. Altogether, this study demonstrates that maxizymes can provide a higher catalytic activity and viral suppression than hRzs.
Mass-Rearing Conditions Do Not Always Reduce Genetic Diversity: The Case of the Mexican Fruit Fly, Anastrepha ludens (Diptera: Tephritidae)
28817Ruiz-Montoya L, Sánchez-Rosario M, López-Gómez E, Garcia-Bautista M, Canedo-Texón A, Haymer D, Liedo P, Insects, 15:56. 2024-01-23 14:31:12.
The application of the sterile insect technique (SIT) requires the adaptation of insects to mass-rearing conditions. It is generally accepted that this adaptation may include a reduction in genetic diversity and an associated loss of desirable characteristics for the effective performance of sterile insects in the field. Here, we compare the genetic diversity of two mass-reared strains of the Mexican fruit fly, Anastrepha ludens, and a wild (WIL) population collected near Tapachula, Mexico, using seven DNA microsatellites as molecular genetic markers. The mass-reared strains were a bisexual laboratory strain (LAB) with approximately 130 generations under mass-rearing and a genetic sexing strain, Tapachula-7 (TA7), also under mass-rearing for 100 generations. Our results revealed an overall low level of genetic differentiation (approximately 15%) among the three strains, with the LAB and WIL populations being genetically most similar and TA7 most genetically differentiated. Although there were some differences in allele frequencies between strains, our results show that overall, the adaptation to mass-rearing conditions did not reduce genetic variability compared to the wild sample in terms of heterozygosity or allelic richness, nor did it appear to alter the level of inbreeding with respect to the wild populations. These results are contrary to the general idea that mass-rearing always results in a reduction in genetic diversity. Overall, our findings can contribute to a better understanding of the impact that adaptation to mass-rearing conditions may have on the genetic make-up of strains.
Wolbachia still works when it is warm
28809McKay, A., Nature Ecology and Evolution, 8. 2024-01-16 13:59:40.
Wolbachia is a maternally inherited endosymbiotic bacterium that can impede the transmission of viruses such as dengue and Zika by some mosquito vectors to humans. Over the past decade, this self-sustaining disease-control method has been rolled out in cities of increasing size; 2023 saw the largest demonstration of efficacy to date, in Medellín, Colombia. However, two key biological mechanisms that enable Wolbachia-carrying mosquitoes to spread in a population — cytoplasmic incompatibility and maternal transmission — have been shown in laboratory conditions to decline under high temperatures. Writing in Nature Climate Change in August 2023, Vásquez and colleagues conducted computational simulations to explore whether near-future warming scenarios are likely to affect the efficacy of Wolbachia-based biocontrol. The models combine empirical estimates of thermal sensitivity for one strain of Wolbachia with projections of future average temperatures and heatwaves for Cairns, Australia and Nha Trang City, Vietnam, two locations where the intervention has been deployed. Estimates of the bacterium’s successful persistence in the mosquito population remain high under tested projections of moderate and severe average warming to 2050. However, the simulations also show reduced efficacy under more variable thermal extremes; these interventions have the potential to fail under extreme warming with long heatwave durations. We selected this paper for our Year in Review collection because it exemplifies how insect thermal biology and global change analysis can offer insights relevant to human health. Testing whether climate change influences Wolbachia-based biocontrol helps to illuminate whether the promising technology is likely to remain feasible in coming years.
Gene drive and genetic sex conversion in the global agricultural pest Ceratitis capitata
28802Meccariello, A., Hou, S., Davydova, S. et al., Nature Communications, 15:372. 2024-01-15 17:13:20.
Homing-based gene drives are recently proposed interventions promising the area-wide, species-specific genetic control of harmful insect populations. Here we characterise a first set of gene drives in a tephritid agricultural pest species, the Mediterranean fruit fly Ceratitis capitata (medfly). Our results show that the medfly is highly amenable to homing-based gene drive strategies. By targeting the medfly transformer gene, we also demonstrate how CRISPR-Cas9 gene drive can be coupled to sex conversion, whereby genetic females are transformed into fertile and harmless XX males. Given this unique malleability of sex determination, we modelled gene drive interventions that couple sex conversion and female sterility and found that such approaches could be effective and tolerant of resistant allele selection in the target population. Our results open the door for developing gene drive strains for the population suppression of the medfly and related tephritid pests by co-targeting female reproduction and shifting the reproductive sex ratio towards males. They demonstrate the untapped potential for gene drives to tackle agricultural pests in an environmentally friendly and economical way.
Programmed evolution: Using asexual gene drives to sculpt tumor populations and combat genetic diversity
28800Justin Pritchard, Scott Leighow, Joshua Reynolds et al., Research Square, 2024-01-15 17:07:16.
Resistance evolution is responsible for the failure of most targeted anticancer therapies. Tumor heterogeneity is so profound that pre-existing resistance is thought to be guaranteed at the time that advanced disease is detected. The practice of waiting for treatment failure and then responding to the refractory tumor with next-generation targeted therapies locks clinicians in an evolutionary arms race until no further treatment options are available. Here, we posit that disease evolution can be reproducibly reprogrammed to design more readily treated tumors, regardless of the exact ensemble of pre-existing genetic heterogeneity. To this end, we conceive of a modular genetic platform that couples an inducible fitness advantage with a shared fitness cost. Using stochastic models of evolutionary dynamics, we identify the design criteria of these “selection gene drives.” We then build prototypes that leverage the selective pressure of various approved tyrosine kinase inhibitors and employ therapeutic mechanisms as diverse as prodrug catalysis and immune activity induction. By using saturating mutagenesis across a drug target and genome-scale loss-of-function libraries, we show that our selection gene drives can eradicate extremely diverse forms of genetic resistance. Finally, using theory to guide treatment scheduling, we demonstrate that model-informed switch engagement can create dramatic in vivo efficacy. These results establish selection gene drives as a powerful new paradigm for evolution-guided anticancer therapy.
Sex or poison? Genetic pest management in the 21st century
28782Luke Alphey, BMC Biology, 21:289. 2024-01-11 13:14:20.
Pests do enormous damage to human and animal health, to agriculture and to biodiversity, with mosquitoes transmitting pathogens, insect larvae eating crops or invasive rodents threatening the last island refuges of endangered birds. This commentary focuses on insects, particularly mosquitoes. However, most considerations apply equally to other pest species. Genetic pest management (GPM) is the use of genetics to control pests through mating of modified pests with their wildtype counterparts. This allows heritable traits to be transferred (“introgressed”) into the wild pest population. In principle, any sexually reproducing pest species can be targeted. The aim is to reduce harm done by the pest population, with typical intended outcomes overwhelmingly falling into two types: population suppression and population modification. For population suppression, one would introgress fitness-reducing traits, such as lethality or sterility, leading to reduction in the numerical size of the pest populations if spread into the target population at sufficiently high frequency. Population modification aims to reduce the harm done by the pest without large changes in the numerical size of the pest population, for example by reducing the ability to transmit disease (“vector competence”) of modified mosquitoes. If such traits, or the DNA sequences encoding them, can be sustained at sufficiently high allele frequency in the target population then the desired harm-reduction outcome should be achieved, by reduction in the number of pests or by reduction in the per-pest harm.
Limited association between Wolbachia and Plasmodium falciparum infections in natural populations of the major malaria mosquito Anopheles moucheti
28760Théo Mouillaud, Audric Berger, Marie Buysse, Nil Rahola, Josquin Daron, Jean-Pierre Agbor, Sandrine N. Sango, Daniel E. Neafsey, Olivier Duron, Diego Ayala, Evolutionary Applications, 16:1999-2006. 2024-01-07 16:47:29.
Since the discovery of natural malaria vector populations infected by the endosymbiont bacterium Wolbachia, a renewed interest has arisen for using this bacterium as an alternative for malaria control. Among naturally infected mosquitoes, Anopheles moucheti, a major malaria mosquito in Central Africa, exhibits one of the highest prevalences of Wolbachia infection. To better understand whether this maternally inherited bacterium could be used for malaria control, we investigated Wolbachia influence in An. moucheti populations naturally infected by the malaria parasite Plasmodium falciparum. To this end, we collected mosquitoes in a village from Cameroon, Central Africa, where this mosquito is the main malaria vector. We found that the prevalence of Wolbachia bacterium was almost fixed in the studied mosquito population, and was higher than previously recorded. We also quantified Wolbachia in whole mosquitoes and dissected abdomens, confirming that the bacterium is also elsewhere than in the abdomen, but at lower density. Finally, we analyzed the association of Wolbachia presence and density on P. falciparum infection. Wolbachia density was slightly higher in mosquitoes infected with the malaria parasite than in uninfected mosquitoes. However, we observed no correlation between the P. falciparum and Wolbachia densities. In conclusion, our study indicates that naturally occurring Wolbachia infection is not associated to P. falciparum development within An. moucheti mosquitoes.
The mosquito knows no borders: Regional challenges for global confrontation in the dengue battle
28789Barçante JMdP, Cherem J, PLoS Neglected Tropical Diseases, 18. 2024-01-04 14:05:29.
Dengue fever is a neglected disease with a global impact, and its incidence and geographical reach are rapidly expanding. Global warming marked by higher average temperatures, precipitation, and longer periods of drought could prompt a record number of dengue fever infections worldwide, due to the thermal biology of mosquitoes. Additionally, increased movement of people, urbanization, and pressure on water and sanitation have driven the spread of dengue fever. The absence of access to tap water leads to an increased reliance on water-storing containers, which can facilitate the breeding of mosquitoes. Similarly, the lack of sanitation can contribute to the formation of small pools of stagnant water, serving as ideal breeding grounds for Aedes. While more prevalent in the tropical and subtropical regions, this viral infection, transmitted by Aedes aegypti and Ae. albopictus mosquitoes, poses a serious public health problem, with outbreaks increasing in number and severity worldwide. In Europe, Aedes mosquito vector species are established in about 22 countries, and dengue fever has been reported for over a decade. In addition to the factors mentioned earlier, the increase in mosquito breeding sites has been identified as a determining factor for the rise in the number of cases.
Consultation on a draft National Gene Drive Policy Guide
28786Commonwealth of Australia (Department of Health and Aged Care), National Gene Technology Scheme, 2024-01-02 13:43:01.
The term gene drive is used to describe organisms which have been genetically modified to increase the rate for a particular trait to spread through a sexually reproducing population, spreading the genes or traits through a species at a faster rate than normal inheritance. An example might be a trait to increase likelihood of offspring to be female and thereby suppress the population of the targeted pest species. The concept of a gene drive is not a new one; these dominant genes – sometimes called selfish genes – are abundant in nature. However, GM gene drive organisms have the potential to be useful for addressing some of the environmental, agricultural, and public health challenges currently faced by Australia, such as conserving native populations, controlling significant exotic pests, or providing public health benefits. As an evolving technology, gene drives may pose risks that are not yet fully understood, including the potential to alter the ecosystem in unpredictable ways. These risks should be acknowledged and managed in a structured and systematic way if Australia wishes to be a future beneficiary of this technology. The Third Review (the Review) of the National Gene Technology Scheme (Scheme), endorsed by all Australian governments on 11 October 2018, recommended “clarifying, and where necessary strengthening, the mechanisms for regulating the environmental release of GM gene drive organisms in Australia” (Recommendation 7b). Review Recommendation 7b and development of the National Gene Drive Policy Guide (Policy Guide) cannot be considered in isolation.
Editorial overview: Conflicts, conflicts everywhere
28768Harmit S Malik, Judith E Mank, Current Opinion in Genetics and Development, 83. 2023-12-31 20:20:14.
Genetic conflicts are pervasive in biology. They arise when genes, sets of genes, or chromosomes enhance their success at significant cost to their genetic neighbors. In some cases, conflicts occur when a ‘cheater’ subverts the rules of genetic inheritance, pitting the interests of the ‘cheater’ against the rest of the genome. In other cases, genetic elements play by the rules of genetic inheritance, but benefit some members of a species at the same time that they harm others. In this issue, we invited a group of scientists at the forefront of the study of different forms of genetic conflicts to share their expertise on some especially intriguing genetic battlegrounds, reflect on their historical underpinnings, summarize current advances, and discuss ideas that will propel the field forward in the years to come. Each of these tales of genetic conflicts is also a tale of evolutionary innovation. Some cases of conflict result from the unique opportunities created by nonfoolproof inheritance rules (e.g. the battle for transmission through gametes or the uniparental inheritance of mitochondria). In other cases, the ‘cheating’ elements (e.g. germline-restricted chromosomes (GRCs)) maintain themselves by creating opportunities to bypass rules their genetic neighbors are forced to abide by. Some conflicts thrive by imposing minimal costs on their neighbors, or even forcing a resolution of conflict so that the interests of all parties are accommodated within the genome. In contrast, others indulge in near-complete chromosomal or gametic fratricide, an observation that is difficult to reconcile without invoking genetic conflicts.
Gene drives, mosquitoes, and ecosystems: An interdisciplinary approach to emerging ethical concerns
28778Ricardo D. Moreno, Luca Valera, Cristián Borgoño, Juan Carlos Castilla, José Luis Riveros, Frontiers in Environmental Science, 11. 2023-12-28 22:14:12.
Gene drives are genetic elements that in sexually reproducing organisms spread faster than those transmitted through a Mendelian fashion. Since gene drives can be engineered to modify different aspects of physiology and reproduction, they have been proposed as a new and revolutionary tool to control vector-borne diseases, particularly those transmitted by the genera Anopheles and Aedes (Culicidae), such as malaria, Dengue and Zika virus. This approach may impact on human health by lowering the transmission of such devastating diseases. However, the release of genetically modified mosquitos (or other species) into the environment raises a series of questions related to the still incipient technology and our present understanding of the complex structure and dynamics of terrestrial and aquatic ecosystems. Moreover, there are ethical concerns about human interventions in natural ecosystems that may eventually impact our way of living or the ecosystems themselves. This work is an interdisciplinary approach that analyzes from a biological, philosophical, and theological perspective the potential ecological impacts on natural environments of the release of genetically modified species, focusing on gene drive-modified mosquitos. It includes theological approach from a Catholic point of view (although it could be easily shared by other Christians) because we hold that world religions give valuable insights even though not everyone may share their groundings. We conclude that the focal problem is the relationship between humans and nature, and the release of genetically modified species may change this relationship unpredictably. However, given the complex interactions in ecosystems, new approaches such as Earth Stewardship principles could provide new and more widely accepted answers involving biological, philosophical, and theological concepts that will help engaging all relevant actors to make a better world.
Antiviral Wolbachia strains associate with Aedes aegypti endoplasmic reticulum membranes and induce lipid droplet formation to restrict dengue virus replication
28757Robson K. Loterio, Ebony A. Monson, Rachel Templin, Jyotika T. de Bruyne, Heather A. Flores, Jason M. Mackenzie, Georg Ramm, Karla J. Helbig, Cameron P. Simmons, Johanna E. Fraser, Applied and Environmental Microbiology, 2023-12-22 16:16:14.
Wolbachia are a genus of insect endosymbiotic bacteria which includes strains wMel and wAlbB that are being utilized as a biocontrol tool to reduce the incidence of Aedes aegypti-transmitted viral diseases like dengue. However, the precise mechanisms underpinning the antiviral activity of these Wolbachia strains are not well defined. Here, we generated a panel of Ae. aegypti-derived cell lines infected with antiviral strains wMel and wAlbB or the non-antiviral Wolbachia strain wPip to understand host cell morphological changes specifically induced by antiviral strains. Antiviral strains were frequently found to be entirely wrapped by the host endoplasmic reticulum (ER) membrane, while wPip bacteria clustered separately in the host cell cytoplasm. ER-derived lipid droplets (LDs) increased in volume in wMel- and wAlbB-infected cell lines and mosquito tissues compared to cells infected with wPip or Wolbachia-free controls. Inhibition of fatty acid synthase (required for triacylglycerol biosynthesis) reduced LD formation and significantly restored ER-associated dengue virus replication in cells occupied by wMel. Together, this suggests that antiviral Wolbachia strains may specifically alter the lipid composition of the ER to preclude the establishment of dengue virus (DENV) replication complexes. Defining Wolbachia’s antiviral mechanisms will support the application and longevity of this effective biocontrol tool that is already being used at scale.
Perspectives of African stakeholders on gene drives for malaria control and elimination: a multi-country survey
28750Finda, M.F., Juma, E.O., Kahamba, N.F. et al., Malaria Journal, 22:8384. 2023-12-21 15:40:51.
Gene drive modified mosquitoes (GDMMs) have the potential to address Africa’s persistent malaria problem, but are still in early stages of development and testing. Continuous engagement of African stakeholders is crucial for successful evaluation and implementation of these technologies. The aim of this multi-country study was, therefore, to explore the insights and recommendations of key stakeholders across Africa on the potential of GDMMs for malaria control and elimination in the continent. A concurrent mixed-methods study design was used, involving a structured survey administered to 180 stakeholders in 25 countries in sub-Saharan Africa, followed by 18 in-depth discussions with selected groups and individuals. Stakeholders were drawn from academia, research and regulatory institutions, government ministries of health and environment, media and advocacy groups. Thematic content analysis was used to identify key topics from the in-depth discussions, and descriptive analysis was done to summarize information from the survey data. Despite high levels of awareness of GDMMs among the stakeholders (76.7%), there was a relatively low-level of understanding of their key attributes and potential for malaria control (28.3%). When more information about GDMMs was provided to the stakeholders, they readily discussed their insights and concerns, and offered several recommendations to ensure successful research and implementation of the technology. These included: (i) increasing relevant technical expertise within Africa, (ii) generating local evidence on safety, applicability, and effectiveness of GDMMs, and (iii) developing country-specific regulations for safe and effective governance of GDMMs. A majority of the respondents (92.9%) stated that they would support field trials or implementation of GDMMs in their respective countries. This study also identified significant misconceptions regarding the phase of GDMM testing in Africa, as several participants incorrectly asserted that GDMMs were already present in Africa, either within laboratories or released into the field. Incorporating views and recommendations of African stakeholders in the ongoing research and development of GDMMs is crucial for instilling stakeholder confidence on their potential application. These findings will enable improved planning for GDMMs in Africa as well as improved target product profiles for the technologies to maximize their potential for solving Africa’s enduring malaria challenge.
Wolbachia infection negatively impacts Drosophila simulans heat tolerance in a strain- and trait-specific manner
28736Liam F Ferguson, Perran A Ross, Belinda van Heerwaarden, bioRxiv, 2023-12-19 16:09:01.
The susceptibility of insects to rising temperatures has largely been measured by their ability to survive thermal extremes. However, until recently, the capacity for maternally inherited endosymbionts to influence insect heat tolerance has been overlooked. Further, the impact of heat on traits like fertility, which can decline at temperatures below the lethal thermal limit has largely been ignored. Here, we assess the impact of three Wolbachia strains (wRi, wAu, and wNo) on the survival and fertility of Drosophila simulans exposed to heat stress during development or as adults. The impact of Wolbachia infection on heat tolerance was generally small and trait/strain specific. Only the wNo infection significantly reduced survival and fertility of adult males after a heat shock. When exposed to a fluctuating heat stress during development, the wRi and wAu strains reduced egg-to-adult survival but only the wNo infection reduced male fertility. Wolbachia densities of all three strains decreased under developmental heat stress, but reductions occurred at temperatures above those that reduced fertility of the host. These findings reveal the complexity of endosymbiont-host-environment interactions and emphasise the necessity to account for endosymbionts and their effect on both survival and fertility when investigating the vulnerability of insects to climate change.
Rapid turnover of pathogen-blocking Wolbachia and their incompatibility loci
28733Shropshire JD, Conner WR, Vanderpool D, Hoffmann AA, Turelli M, Cooper BS., bioRxiv, 2023-12-19 16:02:29.
At least half of all insect species carry maternally inherited Wolbachia alphaproteobacteria, making Wolbachia the most common endosymbionts in nature. Wolbachia spread to high frequencies is often due to cytoplasmic incompatibility (CI), a Wolbachia -induced sperm modification that kills embryos without Wolbachia . Several CI-causing Wolbachia variants, including w Mel from Drosophila melanogaster , also block viruses. Establishing pathogen-blocking w Mel in natural Aedes aegypti mosquito populations has reduced dengue disease incidence, with one study reporting about 85% reduction when w Mel frequency is high. However, w Mel transinfection establishment is challenging in many environments, highlighting the importance of identifying CI-causing Wolbachia variants that stably persist in diverse hosts and habitats. We demonstrate that w Mel-like variants have naturally established in widely distributed holometabolous dipteran and hymenopteran insects that diverged approximately 350 million years ago, with w Mel variants spreading rapidly among these hosts over only the last 100,000 years. Wolbachia genomes contain prophages that encode CI-causing operons ( cifs ). These cifs move among Wolbachia genomes - with and without prophages - even more rapidly than Wolbachia move among insect hosts. Our results shed light on how rapid host switching and horizontal gene transfer contribute to Wolbachia and cif diversity in nature. The diverse w Mel variants we report here from hosts present in different climates offer many new options for broadening Wolbachia -based biocontrol of diseases and pests.
Upper Bound on the Mutational Burden Imposed by a CRISPR-Cas9 Gene-Drive Element
28722Michael S. Overton, Sean E. Guy, Xingsen Chen, Alena Martsul, Krypton Carolino, Omar S. Akbari, Justin R. Meyer, Sergey Kryazhimskiy, bioRxiv, 2023-12-19 12:04:20.
CRISPR-Cas9 gene drives (CCGDs) are powerful tools for genetic control of wild populations, useful for eradication of disease vectors, conservation of endangered species and other applications. However, Cas9 alone and in a complex with gRNA can cause double-stranded DNA breaks at off-target sites, which could increase the mutational load and lead to loss of heterozygosity (LOH). These undesired effects raise potential concerns about the long-term evolutionary safety of CCGDs, but the magnitude of these effects is unknown. To estimate how the presence of a CCGD or a Cas9 alone in the genome affects the rates of LOH events and de novo mutations, we carried out a mutation accumulation experiment in yeast Saccharomyces cerevisiae. Despite its substantial statistical power, our experiment revealed no detectable effect of CCGD or Cas9 alone on the genome-wide rates of mutations or LOH events, suggesting that these rates are affected by less than 30%. Nevertheless, we found that Cas9 caused a slight but significant shift towards more interstitial and fewer terminal LOH events, and the CCGD caused a significant difference in the distribution of LOH events on Chromosome V. Taken together, our results show that these genetic elements impose a weak and likely localized additional mutational burden in the yeast model. Although the mutagenic effects of CCGDs need to be further evaluated in other systems, our results suggest that the effect of CCGDs on off-target mutation rates and genetic diversity may be acceptable.
Assessing the sterility and quality of gamma-irradiated pepper weevils, Anthonomus eugenii (Coleoptera: Curculionidae), toward the development of the sterile insect technique
28713Basso, J.V., Labbe, R. and Scott-Dupree, C., Pest Management Science, 2023-12-18 09:48:19.
The pepper weevil (PW), Anthonomus eugenii, is an economically significant pest of cultivated Capsicum spp. pepper crops in North America where it remains a challenge to manage because of its cryptic immature life stages. The sterile insect technique (SIT) is a genetic pest management tactic that relies on the release of insects that have been sterilized with ionizing radiation to lower the population reproductive rate. Toward developing an effective PW-SIT program, this study has, for the first time, investigated the effects of gamma irradiation on the sterility and survival of this species. Among the array of doses tested, we found that pupal PW males and females irradiated at 110 Gy produced no adult offspring. Furthermore, females mated with a male irradiated at 110 Gy had high egg sterility (97.3%), and irradiated females nearly completely failed to lay eggs (97.5%). Individuals irradiated at this dose had a shortened lifespan (lethal time to 50% mortality values of 12 and 11 days for males and females, respectively) and quantitatively reduced spontaneous flight activity. The eclosion rate of PW pupae was not significantly reduced by any radiation treatment. This study suggests that PWs irradiated at a gamma radiation dose of 110 Gy as pupae could feasibly be used in a PW-SIT program, because both males and females were 100% sterile at this dose. These findings will inform the development of a SIT program that could considerably improve the sustainability and effectiveness of PW management in greenhouse and field pepper crops worldwide.
Procesos celulares modificados en Aedes aegypti infectados con Wolbachia y la susceptibilidad al virus dengue
28696López-Ordóñez T, Díaz-Rodarte KI, Torres-Monzón JA, Casas-Martínez M, Danis-Lozano R, Mosso-González C., Salud Pública de México, 2023-12-12 14:35:34.
Objetivo: Analizar la expresión diferencial de proteínas de Aedes aegypti infectados con Wolbachia y su asociación con el ciclo viral del virus dengue (DENV). Material y métodos. Se revisó una base de datos de proteínas de Ae. aegypti infec-tados y no infectados con Wolbachia, cepa wMel y se buscaron estas en revistas indizadas, que hablaran de la proteína y el ciclo viral de DENV. Resultados: La expresión diferencial de proteínas de los mosquitos durante la infección con Wolbachia intervienen en los procesos de entrada, replicación y salida del DENV. Conclusiones: Existen cambios en la expresión de proteínas de células infectadas con Wolbachia, que son necesarias para el ciclo de replicación de DENV, explicando porque algunos mosquitos infectados con Wolbachia son refractarios a la infección por DENV.
Side effects of X-ray irradiation on flight ability of Cydia pomonella moth
28694Huang, S.-W., Zhang, J.-H., Wei, Z.-H., Yang, X.-M., Wang, X.-Y. and Yang, X.-Q., Pest Management Science, 2023-12-12 14:27:29.
The sterile insect technique (SIT) has proven to be an effective approach in managing the population of major invasive pests Our previous studies showed that irradiation of males at a dosage of 366 Gy X-rays resulted in complete sterility. However, the mating competitiveness of sterilized males is significantly compromised, which can be attributed to a decline in their ability to fly. In this study, we examined the flight patterns of both male and female adults of C. pomonella. The results revealed significant variations in the average flight speed of both genders at different stages of maturity, with females displaying longer flight duration and covering greater distances. Effect of irradiation on the flight performance of 3-day-old male moths was further evaluated, as they demonstrated the longest flight distance. The findings indicated a significant decrease in flight distance, duration, and average speed, due to wing deformities caused by irradiation, which also limited the dispersal distance of moths in orchards, as indicated by the mark-and-recapture assay. Quantitative reverse-transcription PCR analysis revealed a down-regulation of flight-related genes such as flightin, myosin heavy chain, and distal-less following radiation exposure. These findings demonstrate that X-ray irradiation at a radiation dose of 366 Gy has a detrimental effect on the flight ability of male C. pomonella adults. These insights not only contribute to a better understanding of how radiation sterilization diminishes the mating competitiveness of male moths, but also aid in the development and improvement of SIT practices for the effectively controlling C. pomonella.
Aerial release of Aedes aegypti male mosquitoes using an unmanned aerial vehicle: a novel control strategy
28690Valdez-Delgado KM, Ríos-Delgado JC, Nettel-Cruz JA, Angulo-Kladt R, Villarreal-Treviño C., Salud Pública de México, 65. 2023-12-12 14:17:22.
Objective. To development of a methodology for the chilling, handling, transport, and release of male Aedes aegypti mosquitoes, reared in insectary conditions to release in the field with unmanned vehicles to compete sexually with wild males in the field. Materials and methods. A population of Ae. aegypti from different areas in Tapachula, Chiapas, was used. Laboratory tests were conducted: Effect of temperature and cooling time on the knockdown, recovery of males, and copulatory success. Results. The chilling temperature of 3 ± 1ºC for 30 min, was used as a knockdown temperature before handling, packing, transportation, and aerial release. The males subjected to the entire process, including the semi-field aerial release test, showed normal sexual behavior activity, obtaining 100% of females inseminated. Conclusion. These results present the feasibility of applying a new control methodology using unmanned aerial vehicle (UAV) as support for the sterile insect release technique (SIT), use of Wolbachia or both, in male Ae. aegypti, for the design of strategies to control their populations.
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