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A genetically modified (GM) insect is an insect that has been genetically modified, either through mutagenesis, or more precise processes of transgenesis, or cisgenesis. Motivations for using GM insects include biological research purposes and genetic pest management. Genetic pest management capitalizes on recent advances in biotechnology and the growing repertoire of sequenced genomes in order to control pest populations, including insects. Insect genomes can be found in genetic databases such as NCBI, [1] and databases more specific to insects such as FlyBase, [2] VectorBase, [3] and BeetleBase. [4] There is an ongoing initiative started in 2011 to sequence the genomes of 5,000 insects and other arthropods called the i5k. [5] Some Lepidoptera (e.g. monarch butterflies and silkworms) have been genetically modified in nature by the wasp bracovirus. [6]
The sterile insect technique (SIT) was developed conceptually in the 1930s and 1940s and first used in the environment in the 1950s. [7] [8] [9] SIT is a control strategy where male insects are sterilized, usually by irradiation, then released to mate with wild females. If enough males are released, the females will mate with mostly sterile males and lay non-viable eggs. This causes the population of insects to crash (the abundance of insects is extremely diminished), and in some cases can lead to local eradication. Irradiation is a form of mutagenesis which causes random mutations in DNA.
Release of Insects carrying Dominant Lethals or RIDL is a control strategy using genetically engineered insects that have (carry) a lethal gene in their genome (an organism's DNA). Lethal genes cause death in an organism, and RIDL genes only kill young insects, usually larvae or pupae. Similar to how inheritance of brown eyes is dominant to blue eyes, this lethal gene is dominant so that all offspring of the RIDL insect will also inherit the lethal gene. This lethal gene has a molecular on and off switch, allowing these RIDL insects to be reared. The lethal gene is turned off when the RIDL insects are mass reared in an insectary, and turned on when they are released into the environment. RIDL males and females are released to mate with wild males and their offspring die when they reach the larval or pupal stage because of the lethal gene. This causes the population of insects to crash. This technique is being developed for some insects and for other insects has been tested in the field. It has been used in the Grand Cayman Islands, Panama, and Brazil to control the mosquito vector of dengue, Ae. aegypti. [10] [11] [12] It is being developed for use in diamondback moth (Plutella xylostella), [13] [14] medfly ( Ceratitis capitata ) [15] [16] and olive fly (Bactrocera oleae). [17]
There are concerns about using tetracycline on a routine basis for controlling the expression of lethal genes. There are plausible routes for resistance genes to develop in the bacteria within the guts of GM-insects fed on tetracycline and from there, to circulate widely in the environment. For example, antibiotic-resistant genes could be spread to E. coli bacteria and into fruit by GM-Mediterranean fruit flies ( Ceratitis capitata ).
Oxitec released its genetically modified in various countries, including Brazil, Grand Cayman, Malaysia, Panama, and the US.
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The diamondback moth's caterpillars gorge on cruciferous vegetables such as cabbage, broccoli, cauliflower and kale, globally costing farmers an estimated $5 billion (£3.2 billion) a year worldwide. [26] In 2015, Oxitec developed GM-diamondback moths which produce non-viable female larvae to control populations able to develop resistance to insecticides. The GM-insects were initially placed in cages for field trials. Earlier, the moth was the first crop pest to evolve resistance to DDT [27] and eventually became resistant to 45 other insecticides. [28] In Malaysia, the moth has become immune to all synthetic sprays. [29] The gene is a combination of DNA from a virus and a bacterium. In an earlier study, captive males carrying the gene eradicated communities of non-GM moths. [27] Brood sizes were similar, but female offspring died before reproducing. The gene itself disappears after a few generations, requiring ongoing introductions of GM cultivated males. Modified moths can be identified by their red glow under ultraviolet light, caused by a coral transgene. [29]
Opponents claim that the protein made by the synthetic gene could harm non-target organisms that eat the moths. The creators claim to have tested the gene's protein on mosquitoes, fish, beetles, spiders and parasitoids without observing problems. Farmers near the test site claim that moths could endanger nearby farms' organic certification. Legal experts say that national organic standards penalize only deliberate GMO use. The creators claim that the moth does not migrate if sufficient food is available, nor can it survive winter weather. [29]
The Mediterranean fruit fly is a global agricultural pest. They infest a wide range of crops (over 300) including wild fruit, vegetables and nuts, and in the process, cause substantial damage. [30] The company Oxitec has developed GM-males which have a lethal gene that interrupts female development and kills them in a process called "pre-pupal female lethality". After several generations, the fly population diminishes as the males can no longer find mates. To breed the flies in the laboratory, the lethal gene can be "silenced" using the antibiotic tetracycline. [30]
Opponents argue that the long-term effects of releasing millions of GM-flies are impossible to predict. Dead fly larvae could be left inside crops. Helen Wallace from Genewatch, an organisation that monitors the use of genetic technology, stated "Fruit grown using Oxitec's GM flies will be contaminated with GM maggots which are genetically programmed to die inside the fruit they are supposed to be protecting". She added that the mechanism of lethality was likely to fail in the longer term as the GM flies evolve resistance or breed in sites contaminated with tetracycline which is widely used in agriculture. [30]
In July 2015, the House of Lords (U.K.) Science and Technology Committee launched an inquiry into the possible uses of GM-insects and their associated technologies. The scope of the inquiry is to include questions such as "Would farmers benefit if insects were modified in order to reduce crop pests? What are the safety and ethical concerns over the release of genetically modified insects? How should this emerging technology be regulated?" [31]
Drosophila is a genus of flies, belonging to the family Drosophilidae, whose members are often called "small fruit flies" or pomace flies, vinegar flies, or wine flies, a reference to the characteristic of many species to linger around overripe or rotting fruit. They should not be confused with the Tephritidae, a related family, which are also called fruit flies ; tephritids feed primarily on unripe or ripe fruit, with many species being regarded as destructive agricultural pests, especially the Mediterranean fruit fly.
A genetically modified organism (GMO) is any organism whose genetic material has been altered using genetic engineering techniques. The exact definition of a genetically modified organism and what constitutes genetic engineering varies, with the most common being an organism altered in a way that "does not occur naturally by mating and/or natural recombination". A wide variety of organisms have been genetically modified (GM), including animals, plants, and microorganisms.
Drosophila melanogaster is a species of fly in the family Drosophilidae. The species is often referred to as the fruit fly or lesser fruit fly, or less commonly the "vinegar fly", "pomace fly", or "banana fly". In the wild, D. melanogaster are attracted to rotting fruit and fermenting beverages, and are often found in orchards, kitchens and pubs.
Wolbachia is a genus of gram-negative bacteria that can either infect many species of arthropod as an intracellular parasite, or act as a mutualistic microbe in filarial nematodes. It is one of the most common parasitic microbes of arthropods, and is possibly the most common reproductive parasite in the biosphere. Its interactions with its hosts are often complex. Some host species cannot reproduce, or even survive, without Wolbachia colonisation. One study concluded that more than 16% of neotropical insect species carry bacteria of this genus, and as many as 25 to 70% of all insect species are estimated to be potential hosts.
The sterile insect technique (SIT) is a method of biological insect control, whereby overwhelming numbers of sterile insects are released into the wild. The released insects are preferably male, as this is more cost-effective and the females may in some situations cause damage by laying eggs in the crop, or, in the case of mosquitoes, taking blood from humans. The sterile males compete with fertile males to mate with the females. Females that mate with a sterile male produce no offspring, thus reducing the next generation's population. Sterile insects are not self-replicating and, therefore, cannot become established in the environment. Repeated release of sterile males over low population densities can further reduce and in cases of isolation eliminate pest populations, although cost-effective control with dense target populations is subjected to population suppression prior to the release of the sterile males.
Intragenomic conflict refers to the evolutionary phenomenon where genes have phenotypic effects that promote their own transmission in detriment of the transmission of other genes that reside in the same genome. The selfish gene theory postulates that natural selection will increase the frequency of those genes whose phenotypic effects cause their transmission to new organisms, and most genes achieve this by cooperating with other genes in the same genome to build an organism capable of reproducing and/or helping kin to reproduce. The assumption of the prevalence of intragenomic cooperation underlies the organism-centered concept of inclusive fitness. However, conflict among genes in the same genome may arise both in events related to reproduction and altruism.
Aedes aegypti, the yellow fever mosquito, is a mosquito that can spread dengue fever, chikungunya, Zika fever, Mayaro and yellow fever viruses, and other disease agents. The mosquito can be recognized by black and white markings on its legs and a marking in the form of a lyre on the upper surface of its thorax. This mosquito originated in Africa, but is now found in tropical, subtropical and temperate regions throughout the world.
Ceratitis capitata, commonly known as the Mediterranean fruit fly or medfly, is a yellow-and-brown fly native to sub-Saharan Africa. It has no near relatives in the Western Hemisphere and is considered to be one of the most destructive fruit pests in the world. There have been occasional medfly infestations in California, Florida, and Texas that require extensive eradication efforts to prevent the fly from establishing itself in the United States.
Balancer chromosomes are a type of genetically engineered chromosome used in laboratory biology for the maintenance of recessive lethal mutations within living organisms without interference from natural selection. Since such mutations are viable only in heterozygotes, they cannot be stably maintained through successive generations and therefore continually lead to production of wild-type organisms, which can be prevented by replacing the homologous wild-type chromosome with a balancer. In this capacity, balancers are crucial for genetics research on model organisms such as Drosophila melanogaster, the common fruit fly, for which stocks cannot be archived. They can also be used in forward genetics screens to specifically identify recessive lethal mutations. For that reason, balancers are also used in other model organisms, most notably the nematode worm Caenorhabditis elegans and the mouse.
Most animal testing involves invertebrates, especially Drosophila melanogaster, a fruit fly, and Caenorhabditis elegans, a nematode. These animals offer scientists many advantages over vertebrates, including their short life cycle, simple anatomy and the ease with which large numbers of individuals may be studied. Invertebrates are often cost-effective, as thousands of flies or nematodes can be housed in a single room.
Genetically modified animals are animals that have been genetically modified for a variety of purposes including producing drugs, enhancing yields, increasing resistance to disease, etc. The vast majority of genetically modified animals are at the research stage while the number close to entering the market remains small.
Drosophila suzukii, commonly called the spotted wing drosophila or SWD, is a fruit fly. D. suzukii, originally from southeast Asia, is becoming a major pest species in America and Europe, because it infests fruit early during the ripening stage, in contrast with other Drosophila species that infest only rotting fruit.
A gene drive is a natural process and technology of genetic engineering that propagates a particular suite of genes throughout a population by altering the probability that a specific allele will be transmitted to offspring. Gene drives can arise through a variety of mechanisms. They have been proposed to provide an effective means of genetically modifying specific populations and entire species.
Oxitec is a UK-based, US-owned biotechnology company that develops genetically modified insects in order to improve public health and food security through insect control. The insects act as biological insecticides. Insects are controlled without the use of chemical insecticides. Instead, the insects are genetically engineered to be unable to produce offspring. The company claims that this technology is more effective than insecticides and more environmentally friendly.
Scaptomyza flava is an herbivorous leaf mining fly species in the family Drosophilidae. In Latin, flava means golden or yellow. The fly is amber to dark brown in color and approximately 2.5 mm in length. In Europe and New Zealand the larvae are pests of plants in the order Brassicales, including arugula, brassicas, broccoli, Brussels sprouts, bok choy, cabbage, canola, cauliflower, horseradish, kale, kohlrabi, napa cabbage, nasturtium, radish, rapini, rutabaga, turnip, wasabi and watercress. In New Zealand, its range has expanded to include host species that are intercropped with salad brassicas, including gypsophila, otherwise known as baby's breath, which is in the pink family (Caryophyllaceae) and the pea in the Fabaceae. More typically, S. flava is oligophagous within the Brassicales. Scaptomyza are unusual within the Drospophilidae because the group includes species that are truly herbivorous. Other herbivorous drosophilids include D. suzukii, which attacks fruit very early during ripening and species within the genus Lordiphosa, from Africa and Asia, which also include leaf miners. Most drosophilids feed on microbes associated with decaying vegetation and sap fluxes.
The Drosophila quinaria species group is a speciose lineage of mushroom-feeding flies studied for their specialist ecology, their parasites, population genetics, and the evolution of immune systems. Quinaria species are part of the Drosophila subgenus.
On a July 9, 1946, suborbital V-2 rocket flight, fruit flies became the first living and sentient organisms to go to space, and on February 20, 1947, fruit flies safely returned from a suborbital space flight, which paved the way for human exploration. For years before sending mammals into space, such as the 1949 flight of the rhesus monkey Albert II, the Soviet space dogs, or humans, scientists studied Drosophila melanogaster and its reactions to both radiation and space flight to understand the possible effects of space and a zero-gravity environment on humans. Starting in the 1910s, researchers conducted experiments on fruit flies because humans and fruit flies share many genes.
Anthony Mahowald is a molecular genetics and cellular biologist who served as the department chair of the molecular genetics and cellular biology department at the University of Chicago. His lab focused on the fruit fly Drosophila melanogaster, specifically focusing on controlling the genetic aspects of major developmental events. His major research breakthroughs included the study of the stem cell niche, endocycles, and various types of actin.
Genetic incompatibility describes the process by which mating yields offspring that are nonviable, prone to disease, or genetically defective in some way. In nature, animals can ill afford to devote costly resources for little or no reward, ergo, mating strategies have evolved to allow females to choose or otherwise determine mates which are more likely to result in viable offspring.