Difference Between Protoplast and Heterokaryon

Main Difference – Protoplast vs Heterokaryon

Protoplast and heterokaryon are two types of cells widely used in the production of genetically varied cells. The main difference between protoplast and heterokaryon is that protoplast is a plant, a fungal or gram positive bacterial cell whose cell wall has been removed whereas heterokaryon is a multinucleated cell, containing genetically different nuclei of the same species. The protoplast can be recovered by enzymatic or mechanical methods. Protoplasts are widely used in molecular biology to produce genetically modified organisms by transferring foreign DNA. Heterokaryons are generally produced during the sexual reproduction of fungi. In hybridoma technology, heterokaryons are produced by fusing two genetically different cells.

Key Areas Covered

1. What is Protoplast
      – Definition, Features, Uses
2. What is Heterokaryon
      – Definition, Features, Uses
3. What are the Similarities Between Protoplast and Heterokaryon
      – Outline of Common Features
4. What is the Difference Between Protoplast and Heterokaryon
      – Comparison of Key Differences

Key Terms: Anastomosis, DNA Transformation, Heterokaryons, Hybridoma Technology, Hyphae, Mycelium, Plasmolysis, Positive Autotropism, Protoplast, Syncytium 

What is Protoplast

Protoplast can be either a plant, fungal or a gram positive bacterial cell whose cell wall has completely removed by an enzymatical or mechanical method. Plant cells comprise of a cellulose cell wall. The protoplast of plant cells lies within the cell wall. It comprises a plasma lemma in which the contents of the cell can be found. The protoplast can be recovered by artificial plasmolysis using enzymatical or mechanical methods.

Enzymes Used in the Degradation of Protoplasts

Protoplasts are used in the study of membrane biology. In molecular biology, protoplasts are widely used in DNA transformation to produce genetically modified organisms. Protoplasts of a Petunia leaf are shown in figure 1.

Figure 1: Protoplasts

What are Heterokaryons

Heterokaryons are multinucleated cells formed during the sexual reproduction of fungi. Heterokaryons are a type of syncytium in which the fusion of cells forms cell masses with several nuclei. Hyphal tips of the higher fungi adapt to grow towards each other in a process called anastomosis during their sexual reproduction. Anastomosis is a positive autotropism mechanism. During the vegetative growth of hyphae, the tips avoid typically each other. This is negative autotropism. Sexual reproduction is only induced when the fungal hyphae are matured. During anastomosis, two different mycelia of fungi joint into a single mycelium by fusing their cells. Thus, two genetically different nuclei can be found in the same cytoplasm.

Figure 2: Heterokaryon Formation

Sometimes, alleles of the two nuclei can complement each other. Therefore, the morphology such as the branching pattern of the mycelium and the growth rate may depend on the ratio between the different nuclei in the cytoplasm. Thus, heterokaryosis provides genetic variation to the mycelium. These variations can differ in different areas of the mycelium, depending on the ratio between the different nuclei in the mycelium. Artificial heterokaryons are used in the hybridoma technology. The formation of heterokaryons is shown in figure 2. 

Similarities Between Protoplast and Heterokaryon

• Both protoplasts and heterokaryons can be used to form genetically different cells.

Difference Between Protoplast and Heterokaryon

Definition

Protoplast: Protoplast can be a plant, fungal or a gram positive bacterial cell, whose cell wall has been completely removed by an enzymatical or mechanical method.

Heterokaryon: Heterokaryons are multinucleated cells formed during the sexual reproduction of fungi.

Significance

Protoplast: Protoplasts are recovered by the artificial plasmolysis.

Heterokaryon:  Heterokaryons are a type of syncytium.

Types of Cells

Protoplast: Protoplasts can be isolated from plant, fungal or gram positive bacterial cells.

Heterokaryon: Heterokaryons are formed in higher fungi during sexual reproduction.

Number of Nuclei per Cell

Protoplast: Protoplasts consist of a single nucleus per cell.

Heterokaryon: Heterokaryons consist of several, genetically different nuclei per cell.

Variations

Protoplast: Protoplasts can be used to produce genetically modified cells by DNA transformation.

Heterokaryon: Heterokaryon naturally brings variation to the mycelium.

Uses

Protoplast: Protoplasts are used in the studies of membrane biology and transformation of DNA.

Heterokaryon: Heterokaryons are used in the hybridoma technology.

Conclusion

Protoplast and heterokaryon are two types of materials which can be used to produce genetically different nuclei. Protoplast is the content of the cell found inside the cell wall. By removing the cell wall by enzymatic degradation or mechanical methods, the protoplast can be recovered from plant, fungal or gram positive bacterial cells. Heterokaryons are typically formed in higher fungi during sexual reproduction. The fusion of two different mycelia forms a heterokaryotic mycelium with different phenotypic characters. The difference between protoplast and mycelium lies in the number of nuclei in each cell, features as well as the uses of each cell types.

Reference:

1. Shah, Richa. “Protoplasts: Definition, History and Principles | Cell Biology.” Biology Discussion. N.p., 02 May 2016. Web. Available here. 26 July 2017. 
2. Moore, David, Geoffrey D. Robson, and Anthony P. J. Trinci. “Formation of heterokaryons.” 21st Century Guidebook to Fungi. N.p., 01 Dec. 2008. Web. Available here. 27 July 2017. 

Image Courtesy:

1. “Protoplasts Petunia sp” By Mnolf – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “CellFusionTypes” By Gargamol2000 –  (CC BY-SA 4.0) via Commons Wikimedia