Non-Transgenic Gene Editing techniques

Context

• Even as the Centre investigates allegations that unauthorised genetically modified (GM) rice was exported to Europe, it is yet to decide on a research proposal from its own scientists which would allow plants to be genetically modified without the need for conventional transgenic technology.

• Unlike the older GM technology which involves the introduction of foreign DNA, the new proposal involves the use of gene editing tools to directly tweak the plant’s own genes instead.

Key Details on Non-Transgenic Gene Editing techniques

• Scientists at the Indian Agricultural Research Institute are in the process of developing resilient and high-yield rice varieties using such gene editing techniques, which have already been approved by many countries, and they hope to have such rice varieties in the hands of the Indian farmers by 2024.
• However, the proposal for Indian regulators to consider this technique as equivalent to conventional breeding methods, since it does not involve inserting any foreign DNA, has been pending with the Genetic Engineering Appraisal Committee for almost two years.
• The IARI has previously worked on golden rice, a traditional GM variety which inserted genes from other organisms into the rice plant, but ended trials over five years ago due to agronomic issues.

Site Directed Nuclease (SDN) Technologies

• The Indian Agricultural Research Institute has now moved to newer technologies such as Site Directed Nuclease (SDN) 1 and 2. They aim to bring precision and efficiency into the breeding process using gene editing tools such as CRISPR, whose developers won the Nobel Prize for Chemistry in 2020.

  

• In this technologies, scientists are just tweaking a gene that is already there in the plant, without bringing in any gene from outside.
• When a protein comes from an outside organism, then you need to test for safety. But in this case, this protein is right there in the plant, and is being changed a little bit, just as nature does through mutation.
• But it is much faster and far more precise than natural mutation or conventional breeding methods which involve trial and error and multiple breeding cycles. It is potentially a new Green Revolution.
• A research coalition under the Indian Council of Agricultural Research (ICAR), which includes the IARI, is using these techniques to develop rice varieties which are drought-tolerant, salinity-tolerant and high-yielding.
  • However, the draft guidelines for such gene-editing techniques have been stuck with GEAC for almost two years. 

SDN 1 and SDN 2

• The SDN 1 and SDN 2 categories of genome edited plants do not contain any foreign DNA when they are taken to the open field trials.
• The U.S., Canada, Australia and Japan are among the countries which have already approved the SDN 1 and 2 technologies as not akin to GM, so such varieties of rice can be exported without any problem.
• The European Food Safety Authority has also submitted its opinion that these technologies do not need the same level of safety assessment as conventional GM, though the European Union is yet to accept the recommendation.

Back to Basics

What is Genome Editing?

• Genome editing (also called gene editing) is a group of technologies that give scientists the ability to change an organism’s DNA.
• These technologies allow genetic material to be added, removed, or altered at particular locations in the genome.
• Several approaches to genome editing have been developed.

Techs for Genome Editing

The core technologies now most commonly used to facilitate genome editing are

1. Clustered regularly interspaced short palindromic repeats (CRISPR)- associated protein 9 (Cas9)
2. Transcription activator-like effector nucleases (TALENs)
3. Zinc-finger nucleases (ZFNs)
4. Homing endonucleases or meganucleases

About CRISPR

• CRISPR-Cas9 was adapted from a naturally occurring genome editing system in bacteria.
• The bacteria capture snippets of DNA from invading viruses and use them to create DNA segments known as CRISPR arrays.
• The CRISPR arrays allow the bacteria to “remember” the viruses (or closely related ones).
• If the viruses attack again, the bacteria produce RNA segments from the CRISPR arrays to target the viruses’ DNA.
• The bacteria then use Cas9 or a similar enzyme to cut the virus DNA apart, which disables the virus.
• This method is faster, cheaper, more accurate, and more efficient than other existing genome editing methods.

Source: TH

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