Extracting DNA from dried plants – with an eraser

Until now, it hasn’t been possible to get the DNA out of a pressed dried plant (herbarium specimen) without destroying part of it by removing a leaf and grinding it up. 

But new research by scientist Lara Shepherd has proven that you can use an eraser to ‘rub off’ the DNA.

Read Lara’s paper A non-destructive DNA sampling technique for herbarium specimens >

The importance of dried plants to museum collections

Museum collections, including herbarium specimens (pressed dried plants), are becoming an increasingly popular source of DNA for research. They’re a readily-available source of DNA for rare and extinct species and those only found in remote locations.

However, museum specimens are a finite resource so developing methods that minimize damage to them is important.

Melicytus drucei Molloy & B.D.Clarkson, collected 29 Nov 1994, Egmont National Park, Ahukawakawa Swamp, New Zealand. CC BY-NC-ND licence. Te Papa (SP083403)

The nationally endangered Melicytus drucei Molloy & B.D.Clarkson, collected 29 Nov 1994, Egmont National Park, Ahukawakawa Swamp, New Zealand. CC BY-NC-ND licence. Te Papa (SP083403). Removing leaves for DNA research from such a rare and important specimen is undesirable.

DNA from zoological specimens

A number of non-destructive methods have been used to obtain DNA from zoological specimens, including teeth and bones. These normally involve soaking the DNA out of the bone or teeth. However, plant specimens are usually mounted on paper ruling out this approach.

Using erasers to get DNA

My method is based on a technique that has been used to isolate proteins from parchment, which is made from animal skins. I wondered if this method could also be used to also obtain DNA from plants.

Eraser and the erdu created by rubbing a herbarium specimen (pencil for scale).

Eraser and the erdu created by rubbing a herbarium specimen (pencil for scale), 2017. Photograph by Lara Shepherd. Te Papa

I tried rubbing the surface of dried plant specimens with pieces of a special eraser used by museum conservators (but conveniently available from Whitcoulls). The eraser fragments (called erdu) were then used in a normal DNA extraction.

Using this method I was able to get DNA out of half the herbarium specimens that I tried, including from a specimen that was over 70 years old! Most importantly the eraser left no visible damage on the herbarium specimens.

This method worked best for plants that have that have tough leaves. For plants with delicate leaves, I was able to successfully use the eraser on the more robust leaf stalks instead.

This new method will be particularly useful for researching significant specimens, such as name-bearing type specimens and rare and extinct species, for which curators have been reluctant to partially destroy.

Karaka herbarium sample after sampling with an eraser. Sampling site is arrowed.

Karaka herbarium sample after sampling with an eraser (sampling site arrowed), 2017. Photograph by Lara Shepherd. Te Papa

Hen and chickens fern after sampling with an eraser. This species has delicate fronds so the stem was sampled instead. Sampling site is arrowed.

Hen and chickens fern after sampling with an eraser (sampling site arrowed). This species has delicate fronds so the stem was sampled instead, 2017. Photograph by Lara Shepherd. Te Papa

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