Marker genes play a crucial role in genetic transformation by helping scientists identify and select successfully transformed cells — those that have incorporated the desired foreign gene into their genome.
Here’s how they work and why they are important:
- Identification of Transformed Cells:
During genetic transformation, only a small fraction of plant cells actually take up and integrate the introduced DNA. Marker genes are inserted alongside the target gene so that scientists can easily identify which cells have been successfully transformed. - Types of Marker Genes:
- Selectable marker genes: These provide resistance to specific antibiotics or herbicides. For example, the nptII gene (neomycin phosphotransferase II) confers resistance to kanamycin. Only transformed cells survive when grown on media containing the selective agent.
- Reporter marker genes: These produce an easily detectable signal such as color, fluorescence, or luminescence. Examples include GUS (β-glucuronidase) and GFP (Green Fluorescent Protein), which visually confirm gene expression.
- Facilitating Screening and Selection:
Without marker genes, distinguishing transformed cells from untransformed ones would require complex molecular tests. Marker genes make the selection process faster and more reliable. - Temporary Use and Marker-Free Systems:
In modern biotechnology, researchers often remove marker genes after transformation to avoid unnecessary antibiotic or herbicide resistance in the final plant product, especially for biosafety and regulatory reasons.
In summary:
Marker genes act as indicators or selection tools during genetic transformation, ensuring that only those plant cells which have successfully incorporated the desired gene are identified, selected, and further grown into transgenic plants.