How deoxyribonucleic acid (DNA) is extracted from plant cells depends on the process and materials used to remove nuclear material from the cells. Methods differ on cost, complexity and capability, but all methods involve breaking the cell wall and separating insoluble particulates and soluble proteins from the DNA.
Understanding and sequencing plant DNA contributes to our scientific knowledge in forensics, biodiversity, biomass yield, crop improvement and tracking endangered species. According to the U.S. Department of Energy, DNA sequence data "can be applied to the problem of reducing the U.S. dependency on imported oil by improving biomass yield and the efficiency of processes used to convert plant materials into liquid fuels and valuable byproducts."
DNA encodes the genetic information for all living things. The National Health Museum identifies the work of Johann Friedrich Miescher in 1869 as first identifying a "weakly acidic substance of unknown function in the nuclei of human white blood cells." This substance was later called DNA.
However, the scientific community waited until 1953 to understand the double helix structure of DNA based on the work of Francis Crick and James Watson. Once the basic structure of DNA was understood, researchers began the task of isolating DNA from plants and animals, creating and analyzing DNA sequences to understand functions and eventually manipulating the DNA sequences to improve plant's adaptability and production.
Five methods of DNA extraction are common, according to DNA Isolation Methods from Marshall University:
• Salting out using high concentrations of salt to remove proteins and contaminants from the cell. The precipitates are then removed using a centrifuge and the DNA recovered using alcohol.
• Organic extraction mixes dead plant cells with phenol, chloroform and isoamyl alcohol. The DNA is then extracted with an alcohol precipitate.
• A cesium chloride (CsCl) density gradient uses suspended DNA mixed with purified CsCl and ethidium bromide. The product is centrifuged for several hours and then the DNA is extracted with isopropanol.
• Anion-exchange chromatography uses the interaction between a positively charged resin and negatively charged nucleic material to extract the negatively charged DNA.
• Silica-based methods use adsorption of nucleic acids to a silica-gel within a high concentration of salts.
Many people are concerned about the implications of DNA sequencing and modification on bio-diversity and the potential ecological damage from genetically modified plants. There are global concerns about the impact on human health of eating genetically altered crops, as evidenced by the exclusion in Europe of genetically modified crops (New York Times, March 3, 2009).
Scientists like those at the National Institutes of Health and the National Science Foundation are excited about the potential benefit to mankind of learning about and controlling plant genetics. Some positive outcomes envisioned include:
• Plant-based treatment for diseases
• Plants that can adapt to climate change
• Reduced agricultural water consumption
• Greater productivity of food grains to eliminate world hunger
• Plants that can resist insects and diseases