Difference Between Selectable Marker and Reporter Gene

The main difference between selectable marker and reporter gene is that the selectable marker is used to distinguish between transformants and non-transformants whereas the reporter gene is used to measure the level of expression of the transformed gene. Furthermore, selectable marker gene has its own promoter while the expression of reporter gene is regulated by the promoter of the transformed gene.

Selectable maker and reporter gene are two types of genes used to analyze transformants in the studies that produce transgenic organisms.

Key Areas Covered

1. What is a Selectable Marker
     – Definition, Purpose, Examples
2. What is a Reporter Gene
     – Definition, Purpose, Examples
3. What are the Similarities Between Selectable Marker and Reporter Gene
     – Outline of Common Features
4. What is the Difference Between Selectable Marker and Reporter Gene
     – Comparison of Key Differences

Key Terms

Gene Expression Analysis, Gene of Interest, Reporter Gene, Selectable Marker, Transformants

What is a Selectable Marker

Selectable marker is a type of marker genes generally located in the plasmid. It is transformed into the host cell with the help of the plasmid. The transformants that contain the selectable marker can grow in the corresponding selectable medium. But, the non-transformants, which lack the selectable marker, cannot grow in that selectable medium. This means the gene product of the selectable marker becomes the selecting factor for the survival.

The three groups of selectable markers are antibiotic resistance genes, antimetabolite marker genes, and herbicide resistance genes. Most widely used selectable markers are the antibiotic resistance genes. Hence, only the transformants can grow in the medium, which contains the corresponding antibiotic.

Selectable Marker 

Figure 1: Role of Antibiotic Resistant Genes in Molecular Cloning

However, all transformants may not contain the gene of interest. Some transformants may only have the vector with the selectable marker. Sequencing or gene expression analysis only permits the detection of recombinants that have the gene of interest.

What is a Reporter Gene

Reporter gene is a type of marker genes used to quantify the gene expression. They are fused to the regulatory sequence of the gene of interest. Apart from the analysis of the expression of the gene of interest, reporter genes allow studying the function of the gene regulatory elements and the effect of transcription factors on the gene expression. Also, reporter genes are vital in the identification of the tissue-specific or pathway-specific gene expression.

Figure 2: Role of the Reporter Gene

Green fluorescent protein (GFP) and luciferase are the most common type of reporter genes. GFP is a glowing protein under UV light. The presence of other fluorescent proteins such as red and yellow fluorescent proteins allow the identification of different proteins in the same system. Luciferase is an enzyme that catalyzes the production of yellow-green or blue light from the substrate luciferin.

Similarities Between Selectable Marker and Reporter Gene

• Selectable marker and reporter gene are two types of marker genes used to analyze transformants.
• They are transformed into the host organism along with the gene of interest.
• Both types of reporter genes are not present in the host cell under normal conditions. Hence, they are foreign to the host cell.

Difference Between Selectable Marker and Report Gene

Definition

The selectable marker refers to a gene whose expression allows one to identify cells that have been transformed or transfected with a vector containing the marker gene while the reporter gene refers to a gene used to `tag’ another gene or DNA sequence of interest, such as a promoter.

Importance

Selectable marker helps to distinguish between transformants and non-transformants while reporter gene helps to measure the amount of expression of the transformed gene.

Promoter

The selectable marker has its own promoter while reporter gene is regulated under the promoter of the transformed gene.

Location

Selectable maker can be in the plasmid or within the gene construct while reporter gene is in between the promoter and the gene of interest.

Result

Transformed cells with the selectable maker can grow in the selectable medium but, the non transformant cannot grow since they lack the selectable marker while the amount of gene product in the reporter gene depends on the amount of successfully-transformed genes of interest.

Examples

Antibiotic resistance genes, antimetabolite marker genes, and herbicide resistance genes are the types of selectable markers while GFP and Luciferase are some reporter genes.

Conclusion

The selectable markers are the marker genes used to screen transformants in the corresponding selectable medium while the reporter genes are marker genes to measure the amount of expression. The main difference between selectable marker and reporter genes is the type of screening.

Reference:

1. Jha, Nandkishor. “Selectable Marker Genes and Reporter Genes.” Biology Discussion, 16 Oct. 2015, Available Here
2. “Reporter Gene Assays.” Thermo Fisher Scientific, Thermo Fisher Scientific, Available Here

Image Courtesy:

1. “Steps of Molecular Cloning” By Alexpicardal97 – Own work (CC BY-SA 4.0) via Commons Wikimedia 
2. “Reporter gene” By TransControl at en.wikipedia (CC BY-SA 3.0) via Commons Wikimedia