Biju Dharmapalan
Introduction of high-value crops produced through genetic modification helps augment our agricultural chain
The Union Government has allowed genome-edited plants for regulation with the exemption of Site-Directed Nuclease (SDN) 1 and 2 genomes with no foreign DNA. This gives an exemption togenome-edited plants falling under SDN1 and SDN2categories from the Rules,1989. These rules relate to manufacture, use, import, export and storage of hazardous micro-organisms, genetically engineered organisms or cells The genome-edited plants would be now treated as any other plants developed through conventional breeding approaches.
Plant breeding has been a process of trial and error for many years, producing new varieties by mating between parent plants or by self-pollination. This method is based on identifying the desired trait of a plant (for example, higher resistance to a particular disease) and mating it with another plant. This allows the desired trait to appear in the offspring. However, many unwanted traits are also transmitted, so some more breeding cycles need to be replaced with the desired traits. This form of breeding can take years, but this is a very long time given the need to address issues related to climate change and food security quickly. New ways are needed to speed up the process and achieve greater accuracy and efficiency. Several new breeding technologies (NBT) have already been developed, including SiteDirected Nuclease (SDN) technology.
SDN is superior to traditional breeding techniques because it is faster and more targeted. This allows plant breeders to address some of the significant obstacles in plant genomics. The plant genome is diverse in size, ploidy level, heterozygous, and contains highly repetitive genomic regions. In addition, the traits of many plants are determined by multiple genes, making access to some regions of the genome extremely difficult, which poses a significant challenge for plant breeders and scientists. Many important crops are polyploid. They contain a set of two or more pairs of chromosomes from the same (i.e., self-polyploid) or related (i.e., allopolyploid) species.In allopolyploid plants, multiple homoeologs (pairs of genes produced by speciation and recombined by allopolyploidization within the same genome) independently contribute to the phenotype. Induced random mutagenesis performed by irradiation or treatment with chemicals to create random mutations produces only plants with a single mutation in one or another homoeologs. It is doubtful that a double mutation will occur in a particular region of the genome. Time-consuming mating and backcrossing procedures require combining different mutations into one genotype. SDN can target multiple gene copies or gene variants (such as alleles) simultaneously. This is especially useful for polyploids. SDNs can also be specially designed to target specific nucleases to individual alleles.
Site-Directed Nuclease techniques are of three types, SDN-1, SDN-2 and SDN-3. Out of these SDN-1 and 2 don't contain any trace of foreign DNA. However, in SDN-3 foreign DNA may be present.To alter market-oriented traits, site-specific nucleases (SDNs)are increasing rapidly.SDN has expanded the potential for researchers and breeders worldwide to alter the genome of a target organism in very difficult or impossible ways achievable with traditional breeding techniques. Conventional breeding relies primarily on the crossing and selecting offspring with the desired characteristics, sometimes combined with induced non-targeted mutations.
Genome editing research activities are constantly expanding around the world, and more and more plants with market-oriented characteristics are being developed.Companies have already released the first genome-edited crops to the market. Since September 2021, the Sicilian Rouge tomatoes, which are genetically edited to contain high amounts of ?-aminobutyric acid (GABA), have been sold directly to Japanese consumers by Tokyo-based Sanatech Seed. The company claims oral intake of GABA can help support lower blood pressure and promote relaxation.
With the approval of gene-edited plants, India joins the very few world countries that have brought legislation for Gene-Edited crops.The new order that envisages gene-edited plants at par with the conventionally bred plants will boost the morale of our scientific community, who have developed many genetic modifications in plants at the labscale using the CRISPR/Cas technique. But they could not bring them to the public sphere due to the rules that forbid the cultivation of genetically modified plants. We need to find ways to feed the future generation in the changing global scenario. With urbanization going on in every nook and corner of the country, the arable land area is dwindling at a faster pace.In such a scenario feeding the population will be a challenging task. Conventional breeding programmes and agricultural practices may be insufficient. Food security for the next century can be achieved only if we incorporate new molecular breeding techniques.
(The writer is a science communicator and columnist. The views expressed are personal.)
