Scholarly Literature

This is a database of scholarly literature that concentrates currently on natural and engineered selfish genetic elements (gene drives).  The latest are shown here.
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Manipulation of Gut Symbionts for Improving the Sterile Insect Technique: Quality Parameters of Bactrocera dorsalis (Diptera: Tephritidae) Genetic Sexing Strain Males After Feeding on Bacteria-Enriched Diets

17222
Q. Zhang, P. Cai, B. Wang, X. Liu, J. Lin, R. Hua, H. Zhang, C. Yi, X. Song, Q. Ji, J. Yang and S. Chen,  Journal of Economic Entomology,  114:560-570. 2021-01-18 16:16:41.
One environmentally friendly method used to manage Bactrocera dorsalis (Hendel), a key agricultural pest of substantial economic importance, is the sterile insect technique (SIT). Nevertheless, several deficiencies related to this strategy impair the success of the SIT, including the inferior performance of released sterile males compared with wild males, which could be partly solved by the utilization of gut symbionts as probiotic dietary components. In this study, a culture-dependent method was used to isolate and characterize gut-associated bacterial species in adult B. dorsalis genetic sexing strain (GSS) males. In addition, three bacterial isolates from the Enterobacteriaceae family, namely, Enterobacter sp., Morganella morganii, and Moellerella wisconsensis, were used as supplements in larval and adult diets to assess their effects on the life-history traits of irradiated males. Consistent with many previous studies, Enterobacter spp. was shown to be beneficial, with some quality control indices, such as adult size, pupal weight, survival rate under stress and nutritionally rich conditions, and mating competitiveness, being significantly increased, while slight nonsignificant increases in emergence rate and flight ability were observed. Conversely, the M. morganii and M. wisconsensis strains both had negative effects on irradiated male fitness and mating competitiveness. Our results, in combination with those of earlier studies, can contribute to improving the effectiveness of SIT application by enhancing the different aspects of augmentative rearing and biological traits of pests under laboratory rearing conditions.

Widespread haploid-biased gene expression enables sperm-level natural selection

16009
K. Bhutani, K. Stansifer, S. Ticau, L. Bojic, A.-C. Villani, J. Slisz, C. M. Cremers, C. Roy, J. Donovan, B. Fiske and R. C. Friedman,  Science,  eabb1723. 2021-01-14 14:15:08.
Here, we show that a large class of mammalian genes are not completely shared across these bridges. We term these genes “genoinformative markers” (GIMs) and show that a subset can act as selfish genetic elements that spread alleles unevenly through murine, bovine, and human populations. We identify evolutionary pressure to avoid conflict between sperm and somatic function as GIMs are enriched for testis-specific gene expression, paralogs, and isoforms.

Selfing is the safest sex for Caenorhabditis tropicalis

15953
L. M. Noble, J. Yuen, L. Stevens, N. D. Moya, R. Persaud, M. Moscatelli, J. L. Jackson, G. Zhang, R. Chitrakar, L. R. Baugh, C. Braendle, E. C. Andersen, H. S. Seidel and M. V. Rockman,  eLife,  10:e62587. 2021-01-11 16:59:39.
We generated a chromosomal-scale genome for C. tropicalis and surveyed global diversity. Population structure is very strong, and islands of extreme divergence punctuate a genomic background that is highly homogeneous around the globe. Outbreeding depression in the laboratory is caused largely by multiple Medea-like elements, genetically consistent with maternal toxin/zygotic antidote systems. Loci with Medea activity harbor novel and duplicated genes, and their activity is modified by mito-nuclear background. Segregating Medea elements dramatically reduce fitness, and simulations show that selfing limits their spread. Frequent selfing in C. tropicalis may therefore be a strategy to avoid Medea-mediated outbreeding depression.

Population Dynamics of Aedes aegypti and Aedes albopictus in Two Rural Villages in Southern Mexico: Baseline Data for an Evaluation of the Sterile Insect Technique

17758
C. F. Marina, J. G. Bond, K. Hernández-Arriaga, J. Valle, A. Ulloa, I. Fernández-Salas, D. O. Carvalho, K. Bourtzis, A. Dor, T. Williams and P. Liedo,  Insects,  12. 2021-01-11 14:36:35.
Indoor and outdoor ovitraps were placed in 15 randomly selected houses in two rural villages in Chiapas, southern Mexico. In addition, ovitraps were placed in five transects surrounding each village, with three traps per transect, one at the edge, one at 50 m, and another at 100 m from the edge of the village. All traps were inspected weekly. A transect with eight traps along a road between the two villages was also included. Population fluctuations of Aedes aegypti and Ae. albopictus were examined during 2016–2018 by counting egg numbers. A higher number of Aedes spp. eggs was recorded at Hidalgo village with 257,712 eggs (60.9%), of which 58.1% were present in outdoor ovitraps and 41.9% in indoor ovitraps, compared with 165,623 eggs (39.1%) collected in the village of Río Florido, 49.0% in outdoor and 51.0% in indoor ovitraps. A total of 84,047 eggs was collected from ovitraps placed along transects around Río Florido, compared to 67,542 eggs recorded from transects around Hidalgo. Fluctuations in egg counts were associated with annual variation in precipitation, with 2.3 to 3.2-fold more eggs collected from ovitraps placed in houses and 4.8 to 5.1-fold more eggs in ovitraps from the surrounding transects during the rainy season than in the dry season, respectively. Aedes aegypti was the dominant species during the dry season and at the start of the rainy season in both villages. Aedes albopictus populations were lower for most of the dry season, but increased during the rainy season and predominated at the end of the rainy season in both villages. Aedes albopictus was also the dominant species in the zones surrounding both villages. The numbers of eggs collected from intradomiciliary ovitraps were strongly correlated with the numbers of eggs in peridomiciliary ovitraps in both Río Florido (R2adj = 0.92) and Hidalgo (R2adj = 0.94), suggesting that peridomiciliary sampling could provide an accurate estimate of intradomiciliary oviposition by Aedes spp. in future studies in these villages. We conclude that the feasibility of sterile insect technique (SIT)-based program of vector control could be evaluated in the isolated Ae. aegypti populations in the rural villages of our baseline study.

Double drives and private alleles for localised population genetic control

15945
K. Willis and A. Burt,  bioRxiv,  2021.01.08.425856. 2021-01-09 16:30:16.
In this paper we propose and model a series of low threshold double drive designs for population suppression, each consisting of two constructs, one imposing a reproductive load on the population and the other inserted into a differentiated locus and controlling the drive of the first. Simple deterministic, discrete-generation computer simulations are used to assess the alternative designs. We find that the simplest double drive designs are significantly more robust to pre-existing cleavage resistance at the differentiated locus than single drive designs, and that more complex designs incorporating sex ratio distortion can be more efficient still, even allowing for successful control when the differentiated locus is neutral and there is up to 50% pre-existing resistance in the target population. Similar designs can also be used for population replacement, with similar benefits. A population genomic analysis of PAM sites in island and mainland populations of the malaria mosquito Anopheles gambiae indicates that the differentiation needed for our methods to work can exist in nature. Double drives should be considered when efficient but localised population genetic control is needed and there is some genetic differentiation between target and non-target populations.

Targeting evolutionary conserved sequences circumvents the evolution of resistance in a viral gene drive against human cytomegalovirus

15943
M. Walter, R. Perrone and E. Verdin,  bioRxiv,  2021.01.08.425902. 2021-01-08 16:26:29.
Here, we analyze in cell culture experiments the evolution of resistance in a gene drive against human cytomegalovirus. We report that after an initial invasion of the wildtype population, a drive-resistant population is positively selected over time and outcompetes gene drive viruses. However, we show that targeting evolutionary conserved regions ensures that drive-resistant viruses have a replication defect, leading to a long-term reduction of viral levels. This marks an important step toward developing effective gene drives in viruses, especially for therapeutic applications.

Suppression gene drive in continuous space can result in unstable persistence of both drive and wild-type alleles

15938
J. Champer, I. K. Kim, S. E. Champer, A. G. Clark and P. W. Messer,  Mol Ecol,  2021-01-07 19:32:54.
Using spatially explicit simulations, we show that the release of a suppression drive can result in what we term "chasing" dynamics, in which wild-type individuals recolonize areas where the drive locally eliminated the population. Despite the drive subsequently reconquering these areas, complete population suppression often fails to occur or is substantially delayed. This increases the likelihood that the drive is lost or that resistance evolves. We analyze how chasing dynamics are influenced by the type of drive, its efficiency, fitness costs, and ecological factors such as the maximal growth rate of the population and levels of dispersal and inbreeding. We find that chasing is more common for lower efficiency drives when dispersal is low and that some drive mechanisms are substantially more prone to chasing behavior than others. Our results demonstrate that the population dynamics of suppression gene drives are determined by a complex interplay of genetic and ecological factors, highlighting the need for realistic spatial modeling to predict the outcome of drive releases in natural populations.

Demystifying the Risk Assessment Process for Laboratory-Based Experiments Utilizing Invasive Genetic Elements: It Is More Than Gene Drive

18156
Z. N. Adelman,  Applied Biosafety,  2021-01-07 18:05:08.
Advances in recombinant DNA approaches have resulted in the development of transgene architectures that severely bias their own inheritance, a process commonly referred to as ?gene drive.? The rapid pace of development, combined with the complexity of many gene drive approaches, threatens to overwhelm those responsible for ensuring its safe use in the laboratory, as even identifying that a specific transgene is capable of gene drive may not be intuitive. Although currently gene drive experiments have been limited to just a few species (mosquitoes, flies, mice, and yeast), the range of organisms used in gene drive research is expected to increase substantially in the coming years. Here the defining features of different gene drive approaches are discussed. Although this will start with a focus on identifying when gene drive could or could not occur, the emphasis will also be on establishing risk profiles based on anticipated level of invasiveness and persistence of transgenes in the surrounding environment. Attention is also called to the fact that transgenes can be considered invasive without being considered gene drive (and vice versa). This further supports the notion that adequate risk assessment requires information regarding the specific circumstances a given transgene or set of transgenes is capable of invading a corresponding population. Finally, challenges in the review and evaluation of work involving gene drive organisms are discussed.

Ubiquitous Selfish Toxin-Antidote Elements in Caenorhabditis Species

15947
E. Ben-David, P. Pliota, S. A. Widen, A. Koreshova, T. Lemus-Vergara, P. Verpukhovskiy, S. Mandali, C. Braendle, A. Burga and L. Kruglyak,  Current Biology,  2021-01-07 16:57:04.
Here, we report the discovery of maternal-effect TAs in both C. tropicalis and C. briggsae, two distant relatives of C. elegans. In C. tropicalis, multiple TAs combine to cause a striking degree of intraspecific incompatibility: five elements reduce the fitness of >70% of the F2 hybrid progeny of two Caribbean isolates. We identified the genes underlying one of the novel TAs, slow-1/grow-1, and found that its toxin, slow-1, is homologous to nuclear hormone receptors. Remarkably, although previously known TAs act during embryonic development, maternal loading of slow-1 in oocytes specifically slows down larval development, delaying the onset of reproduction by several days. Finally, we found that balancing selection acting on linked, conflicting TAs hampers their ability to spread in populations, leading to more stable genetic incompatibilities. Our findings indicate that TAs are widespread in Caenorhabditis species and target a wide range of developmental processes and that antagonism between them may cause lasting incompatibilities in natural populations. We expect that similar phenomena exist in other animal species.

Next-generation tools to control biting midge populations and reduce pathogen transmission

15940
P. Shults, L. W. Cohnstaedt, Z. N. Adelman and C. Brelsfoard,  Parasites and Vectors,  14:31. 2021-01-07 14:52:23.
Biting midges of the genus Culicoides transmit disease-causing agents resulting in a significant economic impact on livestock industries in many parts of the world. Localized control efforts, such as removal of larval habitat or pesticide application, can be logistically difficult, expensive and ineffective if not instituted and maintained properly. With these limitations, a population-level approach to the management of Culicoides midges should be investigated as a means to replace or supplement existing control strategies. Next-generation control methods such as Wolbachia- and genetic-based population suppression and replacement are being investigated in several vector species. Here we assess the feasibility and applicability of these approaches for use against biting midges. We also discuss the technical and logistical hurdles needing to be addressed for each method to be successful, as well as emphasize the importance of addressing community engagement and involving stakeholders in the investigation and development of these approaches.

Mosquito Sexual Selection and Reproductive Control Programs

15921
L. J. Cator, C. A. S. Wyer and L. C. Harrington,  Trends in Parasitology,  2021-01-06 18:45:40.
Recent work has generated many key insights about specific aspects of mating behavior and physiology. Here, we synthesize these findings and classify swarming mosquito systems as polygynous. Male mating success is highly variable in swarms and evidence suggests that it is likely determined by both scramble competition between males and female choice. Incorporating this new understanding will improve both implementation and long-term stability of reproductive control tools.

Sterile Insect Technique: Principles and Practice in Area-Wide Integrated Pest Management (2nd ed.)

17495
V. A. Dyck, J. Hendrichs and A. S. Robinson,  CRC Press,  2021-01-06 15:33:05.
For several major insect pests, the environment-friendly sterile insect technique (SIT) is being applied as a component of area-wide integrated pest management (AW-IPM) programmes. This technology, using radiation to sterilize insects, was first developed in the USA, and is currently applied on six continents. For almost six decades it has been a major subject for research and development in the Joint FAO/IAEA Programme on Nuclear Techniques in Food and Agriculture, involving both research and the transfer of this technology to Member States so that they can benefit from improved plant, animal and human health, cleaner environments, increased production of plants and animals in agricultural systems, and accelerated economic development. The socio-economic impacts of AW-IPM programmes that integrate the SIT have confirmed the usefulness of this technology. Numerous publications related to the integration of the SIT in pest management programmes, arising from research, coordinated research projects, field projects, symposia, meetings, and training activities have already provided much information to researchers, pest-control practitioners, programme managers, plant protection and animal health officers, and policy makers. However, by bringing together and presenting in a generic fashion the principles, practice, and global application of the SIT, this book serves as a major reference source for all current and future users of the technology, and also serves as a textbook for academic courses on integrated pest management.

Conservation pest control with new technologies: public perceptions

15913
E. A. MacDonald, M. B. Neff, E. Edwards, F. Medvecky and J. Balanovic,  Journal of the Royal Society of New Zealand,  2021-01-04 13:45:38.
We conducted eleven focus groups in New Zealand to explore three questions about novel technologies (gene drive and two others for comparison of pest control tools): (1) what are the risks/benefits? (2) how do they compare to current methods? and (3) who should be represented on a panel that evaluates the tools and what factors should they consider?

Whole-genome resequencing reveals loci with allelic transmission ratio distortion in F1 chicken population

16106
P. Ren, F. Deng, S. Chen, J. Ran, J. Li, L. Yin, Y. Wang, H. Yin, Q. Zhu and Y. Liu,  Molecular Genetics and Genomics,  2021-01-02 15:31:28.
In this study, whole-genome resequencing technology was applied to reveal TRD loci in chicken by constructing a full-sib F1 hybrid population. Through the whole-genome resequencing data of two parents (30 ×) and 38 offspring (5 ×), we detected a total of 2850 TRD SNPs (p-adj < 0.05) located within 400 genes showing TRD, and all of them were unevenly distributed on macrochromosomes and microchromosomes. Our findings suggested that TRD in the chicken chromosome 16 might play an important role in chicken immunity and disease resistance and the MYH1F with significant TRD and allele-specific expression could play a key role in the fast muscle development. In addition, functional enrichment analyses revealed that many genes (e.g., TGFBR2, TGFBR3, NOTCH1, and NCOA1) with TRD were found in the significantly enriched biological process and InterPro terms in relation to embryonic lethality and germline selection. Our results suggested that TRD is considerably prevalent in the chicken genome and has functional implications.

RNA editing controls meiotic drive by a Neurospora Spore killer

24344
N. A. Rhoades and T. M. Hammond,  bioRxiv,  2020.12.30.424869. 2021-01-01 10:39:57.
Neurospora Sk-2 is a complex meiotic drive element that is transmitted to offspring through sexual reproduction in a biased manner. Sk-2’s biased transmission mechanism involves spore killing, and recent evidence has demonstrated that spore killing is triggered by a gene called rfk-1. However, a second gene, rsk, is also critically important for meiotic drive by spore killing because it allows offspring with an Sk-2 genotype to survive the toxic effects of rfk-1. Here, we present evidence demonstrating that rfk-1 encodes two protein variants: a 102 amino acid RFK-1A and a 130 amino acid RFK-1B, but only RFK-1B is toxic. We also show that expression of RFK-1B requires an early stop codon in rfk-1 mRNA to undergo adenosine-to-inosine (A-to-I) mRNA editing. Finally, we demonstrate that RFK-1B is toxic when expressed within vegetative tissue of Spore killer sensitive (SkS) strains, and that this vegetative toxicity can be overcome by co-expressing Sk-2’s version of RSK. Overall, our results demonstrate that Sk-2 uses RNA editing to control when its spore killer is produced, and that the primary killing and resistance functions of Sk-2 can be conferred upon an SkS strain by the transfer of only two genes.Competing Interest StatementThe authors have declared no competing interest.

Transgenic cotton and sterile insect releases synergize eradication of pink bollworm a century after it invaded the United States

15697
B. E. Tabashnik, L. R. Liesner, P. C. Ellsworth, G. C. Unnithan, J. A. Fabrick, S. E. Naranjo, X. Li, T. J. Dennehy, L. Antilla, R. T. Staten and Y. Carrière,  Proceedings of the National Academy of Sciences,  118:e2019115118. 2020-12-28 18:26:42.
The program included releases of billions of sterile pink bollworm moths from airplanes and planting of cotton engineered to produce insect-killing proteins from the bacterium Bacillus thuringiensis. Analysis of computer simulations and 21 y of field data from Arizona indicate these two tactics interacted synergistically to suppress the pest. By eradicating the pink bollworm, the program ended the damage it caused to cotton and the insecticide sprays used to control it, yielding economic, environmental, and social benefits.Invasive organisms pose a global threat and are exceptionally difficult to eradicate after they become abundant in their new habitats.

Genetic pest management and the background genetics of release strains

15695
P. T. Leftwich, L. G. Spurgin, T. Harvey-Samuel, C. J. E. Thomas, L. C. Paladino, M. P. Edgington and L. Alphey,  Philosophical Transactions of the Royal Society B: Biological Sciences,  376:20190805. 2020-12-28 15:35:20.
We discuss issues around strain selection and the potential consequences of such introgression. We conclude that such introgression is probably harmless in almost all circumstances, and could, in theory, provide specific additional benefits to the release programme. We outline population monitoring approaches that could be used, going forward, to determine how background genetics may affect GPM. This article is part of the theme issue ‘Novel control strategies for mosquito-borne diseases’.

Control of malaria-transmitting mosquitoes using gene drives

15693
T. Nolan,  Philosophical Transactions of the Royal Society B: Biological Sciences,  376:20190803. 2020-12-28 15:31:23.
In this article, I will discuss the relative merits of this type of gene drive, as well as barriers to its technical development and to its deployment in the field as malaria control. This article is part of the theme issue ‘Novel control strategies for mosquito-borne diseases'.

Genetic sexing strains for the population suppression of the mosquito vector Aedes aegypti

15691
P. Koskinioti, A. A. Augustinos, D. O. Carvalho, M. Misbah-ul-Haq, G. Pillwax, L. D. d. l. Fuente, G. Salvador-Herranz, R. A. Herrero and K. Bourtzis,  Philosophical Transactions of the Royal Society B: Biological Sciences,  376:20190808. 2020-12-28 15:27:53.
Here, we report on the construction of two genetic sexing strains using red- and white-eye colour mutations as selectable markers. Quality control analysis showed that the Red-eye genetic sexing strains (GSS) is better and more genetically stable than the White-eye GSS. The introduction of an irradiation-induced inversion (Inv35) increases genetic stability and reduces the probability of female contamination of the male release batches. Bi-weekly releases of irradiated males of both the Red-eye GSS and the Red-eye GSS/Inv35 fully suppressed target laboratory cage populations within six and nine weeks, respectively

Wolbachia strain wAlbB maintains high density and dengue inhibition following introduction into a field population of Aedes aegypti

15689
N. A. Ahmad, M.-V. Mancini, T. H. Ant, J. Martinez, G. M. R. Kamarul, W. A. Nazni, A. A. Hoffmann and S. P. Sinkins,  Philosophical Transactions of the Royal Society B: Biological Sciences,  376:20190809. 2020-12-28 15:06:28.
Here, wAlbB-carrying Ae. aegypti collected from the field 20 months after the cessation of releases showed no reduction in Wolbachia density or tissue distribution changes compared to a wAlbB laboratory colony. The wAlbB strain continued to induce complete unidirectional cytoplasmic incompatibility, showed perfect maternal transmission under laboratory conditions, and retained its capacity to inhibit dengue. Additionally, a field-collected wAlbB line was challenged with Malaysian dengue patient blood, and showed significant blocking of virus dissemination to the salivary glands.

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