RNA INTERFERENCE (RNAi) for Trait Improvement

RNAi

a cellular mechanism that silences gene expression by using double-stranded RNA (dsRNA) to target and degrade specific messenger RNAs (mRNAs) or block their translation, effectively preventing protein synthesis.

at early 1990

researchers observed that introducing double-stranded RNA into cells could lead to gene silencing.

Post transcriptional gene silencing

introducing double-stranded RNA into cells could lead to gene silencing

Andrew Fire and Craig Mello (1998)

They demonstrated that double-stranded RNA could be used to inhibit the expression of specific genes in Caenorhabditis elegans (nematodes).

Fire and Mello (2006)

they were awarded with Nobel Prize in Physiology or Medicine

1. Long double stranded RNA (dsRNA) is processed in the nucleus by drosha (RNase enzyme). The resulting shorter dsRNA is exported to the cytoplasm, binds to dicer (RNase enzyme), and is cleaved into small fragments, called small interfering RNAs (siRNAs) or microRNAs (miRNAs), 21-25 base pair RNA strands

2. The siRNA or miRNA is recruited by the RISC complex, unwinds, and incorporates into a protein-RNA complex

3. RISC + siRNA or miRNA bind to a complementary targeted messenger RNA (mRNA)

4. mRNA is cleaved in a specific site and then degraded in the cell, thereby disrupting protein synthesis of the target gene.

Mechanism of RNAi

1. Pest and disease control

   • Trageted pest control

   • Biopesticide

2. Crop improvement

   • Agronomic traits

   • Nutritional quality

   • Oil composistion

RNAi Application

• Ultra-low gossypol cotton seed

• Nutrient-fortified maize

• Transgenic soybean seed

RNAi Sample crops

• RNAi is a universal eukaryotic process, offering safer crop improvement.

• Specifically disrupts pest genes, minimizing harm to non-target species.

• Modifies plant metabolism to boost nutrients and reduce

Advantages

• Can silence non-target genes, risking skewed results.

• May leave residual gene activity, masking true effects.

• Requires repeated applications in some systems unless using stable vectors.

Disadvantages