Gene-edited crops and how the world regulates them
What gene editing is, how it differs from older breeding and transgenic crops, the SDN categories, the first products, and how countries regulate them.
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Gene editing lets breeders change a chosen gene in a crop with a precision that was impossible a decade ago. A few letters of DNA can be altered to switch off a gene that makes a mushroom brown, a tomato lower in a calming compound, or a wheat plant susceptible to mildew, without adding any DNA from another species.
Whether such crops should be regulated like conventional varieties or like genetically modified organisms is one of the most active debates in agricultural policy, and the answer differs by country. The science and the regulation are now standard topics in plant breeding and biotechnology courses and in policy essays.
What gene editing is
Most gene editing in plants uses site-directed nucleases (SDNs): enzymes guided to a specific place in the genome, where they cut the DNA. The cell then repairs the cut, and the repair is where the change happens. The best-known system is CRISPR–Cas9, adapted from a bacterial immune system; Emmanuelle Charpentier and Jennifer Doudna received the 2020 Nobel Prize in Chemistry for developing it. Earlier tools included zinc-finger nucleases and TALENs.
Edits are grouped into three categories by what the repair does:
| Category | What happens | Typical result |
|---|---|---|
| SDN-1 | the cut is repaired by the cell's own error-prone repair, with no template | a small deletion or insertion at the site, often knocking the gene out |
| SDN-2 | a short DNA template guides the repair | a few specific bases changed to a chosen sequence |
| SDN-3 | a long template inserts a whole gene or sequence at the site | a new gene added at a chosen place |
Newer techniques such as base editing and prime editing change individual letters without a full double-strand cut; regulators usually treat them like SDN-1 or SDN-2.
In most methods, the editing machinery is first introduced into the plant as a transgene. Breeders then cross it out, selecting offspring that carry the edit but not the editing genes. The final variety can be free of any foreign DNA.
How it differs from older methods
- Crossing moves thousands of genes at once between related plants; bringing one useful gene from a wild relative into an elite variety takes years of backcrossing, with unwanted genes ("linkage drag") coming along.
- Mutagenesis with radiation or chemicals, used since the 1950s, makes thousands of random changes; breeders screen for the rare useful one. Thousands of varieties of rice, barley, wheat and other crops come from it, and it is generally regulated as conventional breeding.
- Transgenesis (genetic modification as usually understood) inserts a gene, often from an unrelated organism, at a random location. Such crops, like insect-resistant cotton and herbicide-tolerant soybean, are regulated as GMOs almost everywhere.
- Gene editing makes a targeted change at a chosen site. An SDN-1 or SDN-2 edit can produce the same kind of change that could arise by natural mutation or mutagenesis, which is why many regulators treat it differently from transgenesis.
How small is an edit compared with natural variation?
Plants accumulate new mutations every generation. In the model plant Arabidopsis, the measured rate is roughly 7 new mutations per billion DNA bases per generation. Applied, as a rough illustration, to crop genomes (two copies of each chromosome set):
- A rice-sized genome of about 0.4 billion bases: 0.4 × 109 × 2 × 7 × 10−9 ≈ 6 new mutations per plant per generation.
- A bread-wheat-sized genome of about 16 billion bases: 16 × 109 × 2 × 7 × 10−9 ≈ 220.
A field of millions of plants therefore contains enormous numbers of new random mutations every season, and chemical mutagenesis adds thousands per plant. An SDN-1 edit is one designed change, plus any off-target changes, which can be checked by sequencing. The actual rate varies by species and conditions; the point is the order of magnitude, which is central to the argument for treating small edits like conventional breeding.
First products
Gene-edited products are already on the market or approved in several countries, among them:
- A tomato enriched in GABA (a compound marketed for relaxation and blood pressure), on sale in Japan since 2021.
- High-oleic soybean oil in the United States (2019) and gene-edited leafy mustard greens with reduced pungency (2023).
- Fish and livestock traits in some countries, such as faster-growing fish in Japan and slick-coated, heat-tolerant cattle evaluated in the United States.
- Rice varieties with higher yield or better stress tolerance, and soybean, wheat and maize lines in development or approved in Asia, Latin America and Africa.
Traits under development worldwide include disease resistance (for example mildew-resistant wheat and blight-resistant bananas), drought and heat tolerance, lower acrylamide formation in wheat and potato, non-browning produce, reduced allergens, and better nutrition.
Two ways to regulate
Regulation of genetically modified organisms rests partly on the Cartagena Protocol on Biosafety (adopted 2000), which covers living modified organisms that contain "a novel combination of genetic material obtained through the use of modern biotechnology". Whether an edit creates a "novel combination" is the crux of the debate.
Product-based regulation asks what is in the final plant. If a gene-edited plant contains no foreign DNA and could have been produced by conventional breeding or mutagenesis, it is regulated like a conventional variety, sometimes after a notification or consultation. Argentina adopted this approach first, in 2015, and similar rules for SDN-1 (and often SDN-2) products have since been adopted in a growing list of countries across the Americas, Asia, Africa and Oceania, including Brazil, Japan, Australia, several African countries, and others. England passed a Precision Breeding Act in 2023.
Process-based regulation asks how the plant was made. In the European Union, a 2018 ruling of the Court of Justice held that organisms obtained by new mutagenesis techniques, including gene editing, are GMOs under existing law, subject to full risk assessment, traceability and labelling. In 2023 the European Commission proposed a new framework for "new genomic techniques" that would treat simpler edits like conventional plants; its adoption has been the subject of extended negotiation, so check the current status.
Rules are evolving almost everywhere; several countries have revised their guidelines more than once, and some have been challenged in courts. Anyone working with gene-edited material should check the current national rules, and the rules of export markets, which matter when a crop is traded.
The debate
Arguments for lighter regulation of small edits
- The changes are of the same kind as natural and induced mutations already accepted in conventional breeding.
- Heavy GMO-style regulation costs so much that only large companies can afford it; lighter rules let public institutes and small companies in poorer countries develop locally important crops.
- Faster breeding is needed to keep up with climate change and new diseases.
Arguments for caution
- Off-target edits and unintended effects should be checked.
- Regulation based on the process gives consumers and organic producers the ability to know and choose, through traceability and labelling.
- Without labels, edited products may be hard to keep out of organic and GM-free supply chains, which matters for trade.
- Concentration of patents on editing tools and traits could increase corporate control of seeds.
Many scientific academies have concluded that risk should be judged by the traits of the product rather than the method, while noting that public trust, labelling and access to the technology are social choices as much as scientific ones.
Key points
- Gene editing uses site-directed nucleases, chiefly CRISPR–Cas9, to change DNA at a chosen site; the cell's repair makes the edit.
- SDN-1: small changes without a template; SDN-2: template-guided small changes; SDN-3: insertion of a whole gene.
- Edited plants can be free of foreign DNA once the editing genes are crossed out.
- Product-based rules (first Argentina, 2015, now many countries) treat SDN-1 and often SDN-2 products like conventional varieties.
- Process-based rules (the EU since its 2018 court ruling, with reform proposed in 2023) treat all edited plants as GMOs.
- The debate concerns safety, consumer choice, trade, coexistence with organic farming, and who controls the technology.
What the exams ask
- Plant breeding and biotechnology courses: how CRISPR–Cas9 works, SDN categories, base and prime editing, and differences from mutagenesis and transgenesis.
- Research-fellowship and postgraduate entrances: off-target effects, transgene-free editing, examples of edited traits, and the Cartagena Protocol.
- Civil-service and policy examinations: essays comparing product-based and process-based regulation, biosafety, trade and labelling, and access for public-sector breeding.
Described in general terms: the kind of examination, not a past paper. Laisha never reproduces exam questions.
Questions people ask
Is a gene-edited crop a GMO?
It depends on the country and on the kind of edit. Under product-based rules, simple edits without foreign DNA are not treated as GMOs. Under process-based rules, they are. Edits that insert foreign genes are treated as GMOs nearly everywhere.
Can gene-edited plants be detected in a laboratory?
If the edit is known, it can be detected by sequencing or specific tests. But a small SDN-1 edit can look identical to a natural mutation, so proving how it arose may be impossible without records. This makes enforcement of process-based rules difficult.
Will gene editing replace conventional breeding?
No. Editing changes known genes; breeders still need crossing, selection and field testing to combine traits into varieties that perform in farmers' fields. Editing is a powerful addition to the breeder's tools.
Sources
- Jinek, M. et al. "A programmable dual-RNA-guided DNA endonuclease in adaptive bacterial immunity." Science 337, 816–821 (2012).
- Court of Justice of the European Union. Judgment in Case C-528/16, Confédération paysanne and Others, 25 July 2018.
- European Commission. Proposal for a Regulation on plants obtained by certain new genomic techniques, COM(2023) 411.
- Buchholzer, M. and Frommer, W. B. "An increasing number of countries regulate genome editing in crops." New Phytologist 237, 12–15 (2023).
- Ossowski, S. et al. "The rate and molecular spectrum of spontaneous mutations in Arabidopsis thaliana." Science 327, 92–94 (2010).
- Secretariat of the Convention on Biological Diversity. Cartagena Protocol on Biosafety to the Convention on Biological Diversity, 2000.
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