Canadians Find DNA Markers for Barcoding Plants

July 30, 2008 - News Release

Scientists are a step closer to genetically differentiating the more than 300,000 species of plants in the world, thanks to researchers from the University of Guelph, University of British Columbia and University of Toronto.

The Canadian team has compiled a shortlist of genetic markers that can distinguish one plant from another when used in combination. The multi-gene approach was more than 70-per-cent accurate in identifying plants.

Their research was published today in PLoS ONE, a peer-reviewed international journal published by the Public Library of Science.

Scientists in Canada and other countries have been seeking a unique piece of DNA that can be used as a 'barcode' to tell one species from another. A universal barcode system for land plants is vital for cataloguing biodiversity, conducting forensic investigations and tracking endangered and weedy species in the environment, they say.

The research is part of the Canadian Barcode of Life Network, which is based at U of G’s Biodiversity Institute of Ontario. Already, DNA barcoding has led to the discovery of overlooked species of birds, bats, butterflies, fishes and marine algae. But despite the rapid progress in the animal kingdom, plant biologists have had a far more difficult time adopting a universal plant barcode.

"We’ve been delayed by a lack of international consensus over how many and what DNA regions are the most suitable for plant DNA barcoding,” said Aron Fazekas, a post-doctoral researcher in U of G’s Department of Integrative Biology and the study's lead author.

In animals or insects, scientists can identify species with a short DNA sequence from a mitochondrial gene called CO1. But the gene doesn't vary enough in plants to provide reliable species identification.

“A fierce debate has raged about which regions to use, and we’ve been stymied because most individual genes don’t change rapidly enough to pick up species difference,” Fazekas said.

Scientists have now turned to chloroplast genes for the solution (the chloroplast is the “green” plant organelle responsible for photosynthesis). The Canadian researchers set out to find reliable chloroplast markers. They compared nine proposed barcoding regions in plants for their effectiveness in discriminating among a diverse range of species in Ontario.

They purposely targeted several groups of plants that are difficult to distinguish from each other. The researchers found some pairs of species could be distinguished with a single DNA region, but many required two or more regions to be used in tandem. Overall, which chloroplast genes were used mattered less than how many were included.

"Our work provides a resolution to the debate; the number of regions included is the most important factor in a plant DNA barcode,” Fazekas said.

The study's co-authors are: Brian Husband, Steve Newmaster, Mehrdad Hajibabaei and Prasad Kesanakurti, U of G; Sean Graham and Diana Percy, UBC; and Kevin Burgess and project leader Spencer Barrett, U of T.

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