Research & Development

RNAi Technology for Crop Development

RNA interference (RNAi) is a natural cellular process that regulates gene expression by a highly precise mechanism of sequence-directed gene silencing at the translational stage by degrading certain messenger RNAs or inhibiting translation. By mimicking this natural process of gene regulation RNAi technique has been established for therapeutic application both in humans and plants.
RNA interference (RNAi) is a method of inhibiting gene function by inserting short RNA sequences that match a portion of the target gene's sequence, resulting no protein synthesis. RNAi is the tool of choice to figure out the structure and function of essential genes. This technique is also used to alter the gene expression in plants in order to achieve desired traits. RNAi has proved to be a potential tool to battle against the abiotic and biotic stresses. The list of successful applications of RNAi technology now includes enriched nutritional quality, male sterility, delayed ripening, and secondary metabolite manipulation.
The RNAi technique is initiated with the entry of long double stranded RNA (dsRNA), like an introduced transgene, a rogue genetic element or a viral intruder, triggers the cellular RNAi pathway. This involves the enzyme Dicer which cleaves the dsRNA into short, 20-25 base pairs long, fragments, called small interfering RNA (siRNA). On the other hand, an RNA-induced silencing complex (RISC) then distinguishes between the two siRNA strands as either sense or antisense. Then the sense strands (with exactly the same sequence as the target gene) are degraded and the antisense strands on the other hand are incorporated to the RISC. These are used as guide to target messenger RNAs (mRNA) in a sequence-specific manner. Messenger RNAs (mRNA), which codes for amino acids, are cleaved by RISC. The activated RISC can repeatedly participate in mRNA degradation, inhibiting protein synthesis.

The world population is currently around 7.7 billion and it is projected to reach 9.7 billion by 2050. To satisfy the global food demand, improving the production and productivity of food crops is required. Genetic modification is one of the effective methods that has been used recently. Because there are some ethical issues with GM crops that contain foreign genes, the RNAi technology can play an alternate role here by just regulating gene expression.

Report showing RNAi has been used to modify plant metabolic pathways to enhance nutrient content and reduce toxin production. For example, tomato lycopene (carotenoid antioxidant) and flavonoid and b-carotene contents enrichment have been done by targeting Lyc and DET1 gene respectively. Amylose level increment on wheat, sweet potato and maize have been possible for glycemic management and digestive health by targeting SBEII gene.

Tasnin Khan Eusufzai
Scientist
ASRBC