Plant Genomic DNA Extraction Kit (CTAB Crude Extraction Method) Protocol

Plant Genomic DNA Extraction Kit (CTAB Crude Extraction Method) is a specialized reagent kit designed to rapidly isolate high-quality genomic DNA from a wide range of plant tissues using the cetyltrimethylammonium bromide (CTAB) crude extraction strategy.

SKU

P1527546

Reference Catalog

leagene #NE0205

Extraction Method

CTAB Crude Extraction

Key Active Ingredient

Cetyltrimethylammonium Bromide (CTAB)

Intended Sample Type

Plant tissues (leaves, seeds, roots, and other plant materials)

Primary Application

Genomic DNA isolation for downstream molecular biology applications (PCR, sequencing, Southern blotting)

Principle of the CTAB Crude Extraction Method

The CTAB (cetyltrimethylammonium bromide) method is one of the most widely used approaches for isolating genomic DNA from plant tissues. CTAB is a cationic detergent that disrupts cell membranes and forms complexes with nucleic acids, selectively precipitating DNA away from polysaccharides and other contaminants that are abundant in plant cells.

In the crude extraction variant, the procedure is streamlined to reduce the number of steps while still delivering DNA of sufficient quality and quantity for most downstream applications, including PCR amplification, restriction enzyme digestion, and gel electrophoresis. The method relies on cell lysis in a CTAB-containing buffer, followed by organic solvent extraction to remove proteins and lipids, and selective precipitation of DNA.

This approach is particularly advantageous for plant species that are rich in secondary metabolites, polyphenols, and polysaccharides, which can inhibit enzymatic reactions if not adequately removed.

Materials, Reagents, and Equipment

Kit Components (refer to kit manual for exact volumes and concentrations):

• CTAB Extraction Buffer
• Chloroform:Isoamyl Alcohol (24:1) or equivalent organic solvent mixture
• Precipitation reagent (e.g., isopropanol or ethanol)
• Wash buffer
• Elution buffer or nuclease-free water

Additional Materials Required (not supplied):

• Liquid nitrogen or bead mill for tissue homogenization
• Mortar and pestle (pre-chilled)
• Microcentrifuge tubes (1.5 mL or 2 mL)
• Microcentrifuge capable of ≥12,000 × g
• Water bath or heat block set to 65 °C
• Vortex mixer
• Pipettes and aerosol-barrier tips
• Ice bucket

Note: Exact kit component details should be confirmed against the product insert supplied with SKU P1527546 (leagene #NE0205).

Step-by-Step Extraction Protocol

1. Sample Preparation
Harvest fresh plant tissue (typically 50–100 mg leaf material) and immediately freeze in liquid nitrogen. Grind the tissue to a fine powder using a pre-chilled mortar and pestle. Transfer the powder quickly to a pre-chilled 1.5 mL microcentrifuge tube. Avoid thawing during grinding, as this can degrade DNA.

2. Cell Lysis
Add the appropriate volume of pre-warmed CTAB Extraction Buffer (65 °C) to the ground tissue. Vortex vigorously to mix. Incubate at 65 °C for 30–60 minutes, inverting the tube gently every 10 minutes to promote complete lysis.

3. Organic Solvent Extraction
Allow the lysate to cool to room temperature. Add an equal volume of chloroform:isoamyl alcohol (24:1). Mix by gentle inversion for 10 minutes. Centrifuge at 12,000 × g for 10 minutes at room temperature. Carefully transfer the upper aqueous phase to a new tube, avoiding the interphase.

4. DNA Precipitation
Add 0.6–1 volume of isopropanol (or as specified in the kit insert) to the aqueous phase and mix by gentle inversion. Incubate at −20 °C for 20–30 minutes to enhance DNA precipitation. Centrifuge at 12,000 × g for 10 minutes at 4 °C. Discard the supernatant carefully.

5. Washing
Wash the DNA pellet with cold wash buffer (e.g., 75% ethanol). Centrifuge at 7,500 × g for 5 minutes. Remove the wash buffer completely and allow the pellet to air-dry for 5–10 minutes at room temperature. Do not over-dry, as this makes the pellet difficult to dissolve.

6. Elution and Storage
Dissolve the DNA pellet in an appropriate volume of elution buffer or nuclease-free water. Incubate at 55–65 °C for 5 minutes if needed to aid dissolution. Store the extracted DNA at −20 °C for long-term use or at 4 °C for short-term use.

Note: All volumes and incubation times should be verified against the official kit insert for SKU P1527546.

Quality Assessment of Extracted DNA

Spectrophotometric Analysis:
Measure DNA concentration and purity using a UV spectrophotometer (e.g., NanoDrop). A A260/A280 ratio of 1.8–2.0 indicates protein-free DNA. An A260/A230 ratio above 1.8 suggests acceptable removal of polysaccharides, CTAB residues, and phenolic compounds. Values outside these ranges suggest further purification may be needed.

Agarose Gel Electrophoresis:
Run 200–500 ng of extracted DNA on a 0.8% agarose gel. High-molecular-weight genomic DNA should appear as a sharp, distinct band above 10 kb. Smearing below the main band indicates degradation, while a diffuse high-MW band may indicate incomplete lysis or co-purification of RNA.

Functional Verification:
Perform a test PCR with housekeeping gene primers to confirm DNA suitability for downstream applications. Successful amplification of the expected product confirms adequate DNA quality.

Troubleshooting Guide

Problem: Low DNA yield
Possible causes: Insufficient tissue amount; incomplete cell lysis; loss of DNA during organic extraction or precipitation steps.
Solutions: Increase starting tissue amount (within recommended range); ensure complete tissue grinding to fine powder; confirm incubation temperature and time during lysis step; avoid disturbing the pellet when removing supernatant.

Problem: Poor DNA purity (low A260/A280 or A260/A230)
Possible causes: Protein or polysaccharide contamination; residual organic solvent; CTAB carryover.
Solutions: Repeat the chloroform:isoamyl alcohol extraction step; ensure complete removal of wash buffer before elution; consider an additional ethanol precipitation step.

Problem: DNA degradation (smearing on gel)
Possible causes: Endogenous DNase activity; sample thawing during grinding; prolonged processing time.
Solutions: Work quickly and keep samples cold at all steps; add beta-mercaptoethanol to the CTAB buffer if not already included (verify with kit insert); use fresh plant material.

Problem: PCR inhibition despite apparent good DNA quality
Possible causes: Residual polyphenols, CTAB, or polysaccharides acting as PCR inhibitors.
Solutions: Dilute DNA 5–10× before PCR; perform additional purification (e.g., PVPP treatment or column cleanup); verify A260/A230 ratio.

Frequently asked questions

What types of plant tissue are compatible with this CTAB crude extraction kit?

The kit is designed to work with a broad range of plant tissues including leaves, roots, stems, seeds, and fruits. It is particularly effective for tissues rich in polysaccharides or secondary metabolites that typically interfere with standard silica-column DNA extraction methods.

Can the extracted DNA be used directly for PCR without further purification?

In most cases, DNA extracted using the CTAB crude extraction method can be used directly for PCR after appropriate dilution. However, if inhibition is observed (no amplification or weak bands), additional purification steps or further dilution of the DNA template are recommended to remove residual inhibitors such as polyphenols or polysaccharides.

How should the extracted genomic DNA be stored to maintain its integrity?

Extracted plant genomic DNA should be stored at −20 °C for long-term preservation. For frequent short-term access, storage at 4 °C is acceptable. Avoid repeated freeze-thaw cycles, as these can cause DNA shearing and degradation. Storing DNA in elution buffer (TE buffer, pH 8.0) rather than water is recommended to protect against degradation.

Why is beta-mercaptoethanol sometimes added to CTAB extraction buffer?

Beta-mercaptoethanol is a reducing agent that prevents oxidation of phenolic compounds in plant cells. Oxidized polyphenols can bind irreversibly to DNA and proteins, reducing yield and purity. Its addition to the CTAB buffer is particularly important when working with tissues high in tannins or other polyphenols. Always follow the specific kit instructions regarding whether and how much beta-mercaptoethanol to add.

What is the expected DNA yield from this kit?

The expected DNA yield varies depending on the plant species, tissue type, and sample quality. Exact yield specifications for SKU P1527546 should be confirmed in the official product insert. Generally, CTAB-based methods from 100 mg of leaf tissue yield several micrograms of genomic DNA, but this can vary significantly.

References

1. Murray, M.G. & Thompson, W.F. (1980). Rapid isolation of high molecular weight plant DNA. Nucleic Acids Research, 8(19), 4321–4325. doi:10.1093/nar/8.19.4321
2. Doyle, J.J. & Doyle, J.L. (1987). A rapid DNA isolation procedure for small quantities of fresh leaf tissue. Phytochemical Bulletin, 19, 11–15.
3. leagene Plant Genomic DNA Extraction Kit (CTAB Crude Extraction Method) Product Manual, Cat. No. NE0205.

Products are supplied for research and development use only. Not for use in humans, animals, diagnosis, or therapy.