News Column

Pond-dwelling powerhouse's genome points to its biofuel potential

March 7, 2014

By a News Reporter-Staff News Editor at Energy Weekly News -- 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.

Simple and primitive, a duckweed plant consists of a single small kidney-shaped leaf about the size of a pencil-top eraser that floats on the surface of the water with a few thin roots underwater. It grows in almost all geographic areas, at nearly any altitude. Although it's a flowering plant, it only rarely forms small indistinct flowers on the underside of its floating leaves. Most of the time, it reproduces by budding off small leaves that are clones of the parent leaf. It often forms thick mats on the edges of ponds, quiet inlets of lakes and in marshes. It's among the fastest growing plants, able to double its population in a couple of days under ideal conditions.

These and other properties 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.

This genome was sequenced as part of a DOE Office of Science JGI Community Science Program (CSP) project (formerly the Community Sequencing Program). It exemplifies the collaborative approach and innovative projects that the CSP enables among researchers. Messing pointed to the study's advances over previous research.

"The sequencing of this genome opens new frontiers in the molecular biology of aquatic plants," said Messing. "This publication represents the single largest advance in this field and a new milestone in plant molecular biology and evolution, as previous studies were either classical botany or biochemistry of photosynthesis. The placement of the Spirodela genome as a basal monocot species will serve as a new reference for all flowering plants."

Keywords for this news article include: Biotechnology, Energy, Biofuel, Oil and Gas, Bioengineering, DOE/Joint Genome Institute, Government Agencies Offices and Entities.

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Source: Energy Weekly News

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