Cool Plant Tools: DNA Barcoding

Scanning Plants?

Wouldn’t it be cool to be able to identify all the different plant species in your backyard or in a nearby park from just small pieces of their leaves?

And how cool would it be to use a smartphone app to determine exactly what kind of plants are actually in the herbal supplement you’re taking or the tea you’re drinking?

Plant scientists (and even some citizen scientists) are currently able to do this thanks to a relatively new technology called DNA barcoding.

DNA barcoding is based on the premise that individual plant species each possess unique versions (DNA sequence) of several key genes shared by all plants.

I won’t go into detail in describing how DNA barcoding works, simply because it is described so well at other places online. For example, see CSHL Biology Animation Lab : DNA barcoding as a place to start, and for more detailed information please see DNA barcoding 101 (Cold Spring Harbor Labs).

Briefly, here are the five basic steps of DNA barcoding:

Step 1: Collect a small amount (about 1/2 teaspoon full) of plant material. This is pretty easy.

Step 2: Extract all of the DNA from this plant material. This is relatively cheap and easy, even schoolchildren do it.

Step 3: From your DNA sample, use PCR to amplify (make millions of copies) of the key genes (typically, only two) in question. To do this you need a thermal cycler and specific DNA primers for each of the genes in question. This is fairly difficult if you’re not already set up to do it, although one can build a cheap (under $100) thermal cycler. (Alternatively, if you have a local DIY Bio group in your city, you might be able to do it there.)

Step 4: Sequence the DNA for each of these genes. This requires an expensive DNA sequencer machine, but most people send it to a commercial gene-sequencing lab, costing relatively little. (A couple hundred bucks?)

Step 5: Compare your DNA sequences with known plant gene sequences in a gene sequence (“barcode”) database – a reference library of DNA sequences (“barcodes”) that can be used to assign identities to unknown specimens.

Part of a DNA sequence and its corresponding "barcode"

Part of a DNA sequence and its corresponding “barcode”

Who Uses This Technology?

There are two categories of DNA barcode users, taxonomists and people in fields other than taxonomy.

Some taxonomic examples include the Smithsonian National Museum of Natural History Project and Plant DNA barcoding at the New York Botanical Garden.

Although this is a new technology, it has already proven to be very useful. For example, Wales has become the first country to DNA barcode all its flowering plants. And DNA barcoding has also been used in the conservation of endangered plants, including barcodes for trees and DNA barcoding wild Alaskan plants by citizen scientists.

In realms of plant science other than taxonomy, scientists have, for example, discovered the utility of barcoding for the identification of plant roots.

DNA barcoding has also been used to determine the actual composition of herbal supplements and to
identify tea ingredients.

In a recent finding, microbial DNA barcoding was used to analyze the what microbes were present on the surface of wine grapes grown in different regions. The conclusion: the fungi and bacteria that grow on the surface of the wine grape may make each region’s wine unique.

The science of DNA barcoding is, however, still a work-in-progress. There remain important
challenges in the DNA barcoding of plant material, for example.

Despite these challenges, DNA barcoding may be on the verge of revolutionizing everyday life.

More Online Resources:

Barcode of LifeIdentifying species with DNA barcoding

The Barcode BlogA mostly scientific blog about short DNA sequences for species identification and discovery.

Recent News: Tell me your barcode, and I’ll tell you what palm tree you are

Reference

1. Hollingsworth, P. M., S. W. Graham, and D. P. Little (2011) “Choosing and Using a Plant DNA Barcode.” PLoS ONE 6(5): e19254. doi:10.1371/journal.pone.0019254. (Full Text)

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