Pond-dwelling powerhouses genome points to its biofuel potential

Duckweed is a tiny floating plant that's been known to drive people daffy. It's one of the smallest and fastest-growing flowering plants that often becomes a hard-to-control weed in ponds and small lakes.

But it's also been exploited to clean contaminated water and as a source to produce pharmaceuticals. Now, the genome of Greater Duckweed (Spirodela polyrhiza) has given this miniscule plant's potential as a biofuel source a big boost.

In a paper published February 19, 2014 in the journal Nature Communications, researchers from Rutgers University, the Department of Energy Joint Genome Institute and several other facilities detailed the complete genome of S. polyrhiza and analyzed it in comparison to several other plants, including rice and tomatoes.

Properties of duckweed make it an ideal candidate as a biofuel feedstock – a raw source for biofuel production. For example, unlike plants on land, duckweeds don't need to hold themselves upright or transport water from distant roots to their leaves, so they're a relatively soft and pliable plant, containing tiny amounts of woody material such as lignin and cellulose. Removing these woody materials from feedstock has been a major challenge in biofuel production. Also, although they are small enough to grow in many environments, unlike biofuel-producing microbes, duckweed plants are large enough to harvest easily.

S. polyrhiza turns out to have one of the smallest known plant genomes, at about 158 million base pairs and fewer than 20,000 protein-encoding genes. That's 27 percent fewer than Arabidopsis thaliana – which, until recently, was believed to be the smallest plant genome – and nearly half as many as rice plants.