Genetically modified insect

The fruit-fly Drosophila melanogaster, often used in genetic modification studies

A genetically modified insect is an insect that has been genetically modified for various reasons such as agricultural production, oil production and pest control.

In biological research, transgenic fruit flies (Drosophila melanogaster) are model organisms used to study the effects of genetic changes on development. Fruit flies are often preferred over other animals due to their short life cycle, low maintenance requirements, and relatively simple genome compared to many vertebrates.

Methods

See also: Sterile insect technique

The first release of modified mosquitoes were performed in the 1970s. It was mosquitoes of the species that transmit the dengue virus, that were sterilised by irradiation (sterile insect technique).

The British company Oxitec use a technique called RIDL (Release of Insects with Dominant Lethality), that can produce fertile male adults that induce a high mortality of the descendants. The adults generated with this technique and released in the environment are not sterile but their descendants have a survival rate of 0% (this lethality can be switched off by introducing the antibotic, tetracycline, into their diet). This company is currently(written 3/23/15) working on releasing these insects into Florida Keys, reducing the amount of wild insects that carry disease.

Concerns

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). GM olive flies and diamondback moths (Plutella xylostella) may also spread antibiotic resistance genes into the food chain via olives or brassica crops, affecting animals that eat them. Other species, such as rodents, flying squirrels or earthworms could also play a role in disseminating antibiotic resistance, perhaps into diseases that they carry. Antibiotic resistance genes in the guts of GM-mosquitoes may be transferred to animals directly if they are swallowed as adults, or passed on to mates and larvae and thus to water supplies. Breeding GM-insects using tetracycline breaches existing policies. These advise against mass feeding of antibiotics to animals worldwide and in some countries, the practice is banned, e.g. in the E.U. and Brazil.

Modified species

For confined scientific research

• Drosophila melanogaster

For commercial uses

• Yellow fever mosquito (Aedes aegypti)
• Malaria mosquito (Anopheles gambiae and Anopheles stephensi)
• Pink bollworm (Pectinophora gossypiella)

Diamondback moth

Diamondback moth

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 million) a year worldwide. 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 and eventually became resistant to 45 other insecticides. In Malaysia, the moth has become immune to all synthetic sprays. 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. 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.

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.

Mediterranean fruit fly

Mediterranean fruit fly

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. 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.

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.

Legislation

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?"

See also

• Inherited sterility in insects
• List of sterile insect technique trials
• Insect ecology
• Detection of genetically modified organisms

External links

• Transgenic Fly Virtual Lab - Howard Hughes Medical Institute BioInteractive