When it comes to DNA extraction, most people tend to think of blood or tissue samples like hair, muscle, or bones. But what about plants? Though plants are probably not the first to come to mind when thinking of DNA extraction, they are made up of dermal, vascular, and ground tissues that can be used to extract DNA. Primary dermal tissues, called the epidermis, make up the outer layer of all plant organs (e.g., stems, roots, leaves, flowers). Extractions from these tissues play a crucial role in agriculture and ensuring the security of the food supply chain, in addition to horticultural and biodiversity studies.
Unlike animal cells, which are enveloped in a soft phospholipid bilayer membrane, plant cells have an additional outer cell wall made of cellulose that provides rigidity to their cells. DNA extraction from plant tissues, such as leaves, requires the breakdown of the rigid cell wall either by chemical, enzymatic, mechanical means, or some combination of these three methods. Plant DNA extraction requires homogenization to remove cell walls and a soapy substance to degrade lipid membranes. Next, the separated DNA from the mixture is precipitated by using alcohol. Extraction of high-quality and pure DNA is a difficult task and requires complex processing. Some plant cells’ metabolites may contaminate DNA during precipitation and interfere with DNA extraction. Comparatively, animal cells have no cell wall to break down, thus making the extraction process less troublesome.
There are three main types of lysis for DNA extraction from plant tissues:
The rigid cellulose wall of plant cells lends itself well to protecting the internal structures of a plant, but this protection can present an obstacle to scientists trying to extract DNA. Mechanical rupture of this cell wall is often accomplished by mortar and pestle, bead beating, sonication, freeze-thaw cycles, or high temperatures. These extreme physical disruptions to the plant sample can enable the breakdown of cell walls.
Enzymatic lysis of plant cells is often used in conjunction with mechanical lysis to ensure complete breakdown of the plant cell wall. Common enzymes for this process include cellulases, chitinases, lysozymes, and more. These enzymes target specific components of the extracellular matrix, such as cellulase specifically targeting cellulose.
The chemical composition of the cell wall includes polysaccharides, cellulose, and pectin. Other polymers such as lignin, suberin, or cutin are often anchored to or embedded in cell walls. Targeting these polymers with the appropriate chemical substance can dissolve them. Some methods use hazardous chemicals like ether, chloroform, and alcohol. Alternatively, there are safer, non-organic solvents such as Cetyltrimethylammonium Bromide (CTAB) Buffer.
Leaf tissue generally contains high amounts of polysaccharides, polyphenols, and tannins, which can contaminate DNA and affect downstream analyses like polymerase chain reaction (PCR). There is a need to remove these metabolites after lysis and extraction.
Many industries are utilizing DNA extraction from plants for genetic modification. Researchers can engineer a plant with seeds inheriting modified genes by isolating DNA from organisms with desirable traits, such as resistance to pesticides, and injecting them into the target plant’s genome. Also, plant pathologists can study the genetic causes of plant disease by analyzing their DNA. Agriculturalists may use extracted DNA to find mutations affecting a plant’s growth rate.
Omega Bio-tek’s E.Z.N.A.® HP Plant & Fungal DNA Kit can process challenging samples rich in polysaccharides, polyphenolic compounds, and enzyme inhibitors to isolate high-quality DNA that does not hamper downstream applications. These kits extract high-yield and high-quality DNA that uses CTAB ionic detergent and eradicates chloroform extractions. Read more about extracting DNA from plants vs animals here.
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