Virus-Induced Gene Silencing
A high-speed lane for plant functional genomics.
What is VIGS?
Virus-Induced Gene Silencing (VIGS) is a revolutionary reverse genetics technique that harnesses a plant's natural viral defense system—RNA interference (RNAi)—to temporarily "turn off" specific genes. By observing the resulting changes in the plant, scientists can rapidly deduce a gene's function. It's a powerful, fast, and efficient method to decode the secrets of the plant genome.
Phenotypes in Weeks, Not Years
The VIGS Mechanism: A Biological Relay
1. Viral Vector
A modified virus carries a fragment of the target gene.
2. RNAi Trigger
The virus produces double-stranded RNA (dsRNA) in the plant.
3. Gene Silencing
The plant's defense machinery degrades the target gene's mRNA.
4. Phenotypic Analysis
Observable changes in the plant reveal the gene's function.
Driving Discovery: Key Applications
Gene Function Studies
Rapidly identify the roles of genes in development, metabolism, and stress response.
Pathway Analysis
Investigate complex gene interactions within biochemical or signaling pathways.
Crop Improvement
Screen for valuable traits like disease resistance, drought tolerance, or improved yield.
The VIGS Toolkit: Common Viral Vectors
Different viruses are suited for different plants. This chart compares the relative host range breadth of popular VIGS vectors.
Challenges & Considerations
While powerful, VIGS has limitations. This chart visualizes the relative impact of common challenges.
The VIGS Lab Workflow
1
Design Gene Fragment
A ~300bp unique sequence of the target gene is cloned into the VIGS viral vector.
2
Inoculation
The recombinant virus is introduced into the plant, usually via Agroinfiltration.
3
Systemic Spread
The virus replicates and spreads throughout the plant's tissues.
4
Silencing Activation
The plant's RNAi machinery recognizes the viral dsRNA and gets activated.
5
mRNA Degradation
The machinery degrades the target gene's mRNA, leading to silencing.
Notes for Study purpose
Virus-Induced Gene Silencing (VIGS)
Virus-Induced Gene Silencing (VIGS) is a powerful reverse genetics tool used in plant molecular biology to study gene function. It utilizes the plant's own RNA interference (RNAi) machinery to silence specific genes, offering a rapid, transient, and efficient method for functional genomics.
(OR)
Virus-induced gene silencing (VIGS) is a powerful technique used in molecular biology to study gene function in plants. It leverages the natural defense mechanism of plants against viruses to silence specific genes, allowing researchers to observe the resulting phenotypic changes
Viral Vector: A modified virus (often a plant virus like Tobacco rattle virus or Potato virus X) is used as a vector to carry a fragment of the target gene sequence.
RNA Interference (RNAi): When the virus infects the plant, it produces double-stranded RNA (dsRNA) from the inserted gene fragment. This triggers the plant's RNAi pathway, which degrades the dsRNA and homologous mRNA of the target gene, effectively silencing it.
Phenotypic Analysis: The silencing of the target gene leads to observable changes in the plant's traits (e.g., altered leaf color, growth patterns), revealing the gene's function
Applications
Gene Function Studies: Identify roles of specific genes in development, stress response, or metabolism.
Pathway Analysis: Investigate gene interactions in biochemical or signaling pathways.
Crop Improvement: Screen genes for traits like disease resistance or improved yield.
Limitations
Incomplete Silencing: Gene suppression may not be uniform or complete.
Off-Target Effects: Non-specific silencing can occur if the inserted sequence shares homology with other genes.
Virus Effects: The viral infection itself may cause symptoms that complicate phenotype interpretation.
Species Specificity: Not all plants are equally susceptible to VIGS vectors.
Design Gene Fragment: A short sequence (~200–500 bp) of the target gene is cloned into a VIGS vector (modified viral genome).
Agroinfiltration or Mechanical Inoculation: The recombinant virus is introduced into the plant (usually via Agrobacterium tumefaciens).
Systemic Spread: The virus spreads throughout the plant and expresses the inserted gene fragment.
RNA Silencing Activation: The plant recognizes the double-stranded RNA as foreign and activates its RNAi machinery.
mRNA Degradation: Both viral RNA and the host mRNA with similar sequences are degraded, leading to gene silencing.
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