Why Sequence the Greater Duckweed?

The Lemnaceae, commonly known as duckweeds, are the smallest, fastest growing and simplest of flowering plants. Some of the current uses of Lemnaceae are a testimony to its utility: basic research and evolutionary model system, toxicity testing organism, biotech protein factory, wastewater remediator, high-protein animal feed, and carbon cycling participant. Sequencing of the Greater Duckweed, Spirodela polyrhiza (L.) Schleiden, which has a genome size similar to that of Arabidopsis (150 MB), will address challenges in alternative energy, bioremediation, and global carbon cycling.

Duckweed photo courtesy Todd Michael.

With the passage of the 2005 Federal Energy legislation, the drive to develop sustainable feedstocks and processing protocols for biofuel production has intensified. The search for new biomass species has revealed the potential of Lemnaceae species. These plants produce biomass faster than any other flowering plant. The carbohydrate content of the plant material also indicates a potential for ethanol production. Moreover, the carbohydrate in duckweed biomass is readily converted to fermentable sugars by using commercially available enzymes developed for corn-based ethanol production.

The utility of Lemnaceae species for bioremediation has long been recognized as well. Propagated on agricultural and municipal wastewater, Spirodela and related species efficiently extract excess nitrogen and phosphate pollutants. Duckweed growth on ponds effectively reduces algal growth (by shading), coliform bacterial counts, suspended solids, evaporation, biological oxygen demand, and mosquito larvae while maintaining pH, concentrating heavy metals, sequestering or degrading halogenated organic and phenolic compounds, and encouraging the growth of other aquatic animals such as frogs and fowl.

A better understanding of Lemnaceae species could also reveal the potential for their role in the global carbon cycle. Primitive aquatic plants have been implicated as the primary source of carbon sequestration that drove global climate change during the Early Eocene. The S. polyrhiza genome sequence could unlock the remarkable potential of a rapidly growing aquatic plant for carbon sequestration, carbon cycling, and biofuel production.

Principal Investigators: Todd P. Michael, Randall Kerstetter, and Joachim Messing (Rutgers); John Shanklin and Jorg Schwender (Brookhaven Natl. Lab.), Elias Landolt (Institut f�r Integrative Biologie, Switzerland), Klaus Appenroth (Univ. of Jena, Germany), Tokitaka Oyama (Kyoto Univ.), Todd Mockler (Oregon State Univ.)

Program: CSP 2009