Eucalyptus Tapped as the Next Tree Genome to be Sequenced, Characterized & Harnessed for Bioenergy, Carbon Sequestration, and other Industrial Applications

An ambitious international effort has been launched to decode the genome of Eucalyptus, one of the world’s most valuable fibre and paper-producing trees-with the goal to maximize its potential in the burgeoning bioenergy market and for capturing excess atmospheric carbon.

The scientific effort to characterize the Eucalyptus genome, uniting some two dozen institutions world-wide, is led by Alexander Myburg of the University of Pretoria (South Africa), with co-leads Dario Grattapaglia, of EMBRAPA and Catholic University of Brasília (Brazil) and Gerald Tuskan of Oak Ridge National Laboratory (United States). The DNA sequence of the 600-million-nucleotide tree genome will be generated under the auspices of the U.S. Department of Energy Joint Genome Institute (DOE-JGI) Community Sequencing Program (CSP) and the information will be made freely available over the Worldwide Web.

“Sequencing the Eucalyptus genome will help us overcome many of the major obstacles toward achieving a sustainable energy future,” said Myburg. “Embedded in this information is the molecular circuit map for superior growth and adaptation in woody plants that can be optimized for biomass production. Its unique evolutionary history, keystone ecological status, and adaptation to marginal environments make Eucalyptus the focus of choice for expanding our knowledge of the evolution and adaptive biology of all perennial plants.”

The genus Eucalyptus, comprised of over 700 different species, include some of the fastest growing woody plants in the world and, at approximately 18 million hectares in 90 countries, it is one of the most widely planted genus of plantation forest trees in the world. These trees evolved in the Southern Hemisphere quite separately from Northern Hemisphere tree species. Only the second tree to be sequenced, Eucalyptus offers extraordinary opportunities for comparative genomic analysis with Populus, the first tree sequenced and published in the journal Science by DOE JGI and collaborators in 2006.

“The Eucalyptus genome will provide a window into the tree’s metabolic pathways, shedding light on such traits as cold tolerance, osmotic potential, membrane integrity, and other agronomic features,” said co-lead Tuskan. “As the genus is amenable to genetic transformation, it can serve as a validation platform for candidate gene expression studies-helping us to expand Eucalyptus’ range and exploit its potential as a bioenergy plantation crop,”

“This monumental project will enable improved breeding strategies for cellulosic ethanol feedstocks and contribute to environmentally sound improvements in productivity for the global forestry industry,” said project collaborator Barbara Wells, President and CEO of ArborGen, LLC, a U.S.-based forestry biotechnology company. “This effort will help us advance our goals of producing renewable high-value biomass from a smaller environmental footprint.” Wells added that ArborGen brings a wealth of experience with Eucalyptus and its enormous potential as a dedicated bioenergy crop, noting that “this fast growing, high yield tree offers a new source of hardwood in the Southern U.S. that can play a key role in national energy security and economic development in the region, in addition to providing numerous environmental benefits.”

Already, a considerable amount of carbon is tied up in Eucalyptus biomass. Coupled with the emerging economic incentives for carbon sequestration, Eucalyptus is a prime candidate for increased efforts to remove carbon from the atmosphere. “In countries such as Brazil, Eucalyptus is used as a source of renewable energy for high quality steel production in a way that reduces the net production of greenhouse gases. Eucalyptus is capable of sequestering carbon at rate of 10 tons of carbon/hectare/year and has a positive net carbon balance even when it is used to generate energy from charcoal or for pulp and paper production. Furthermore plantation forestry of Eucalyptus plays a crucial role to reduce the pressure on tropical forests and associated biodiversity” said project co-lead Grattapaglia.

“From a phylogenetic standpoint,” said project collaborator Brad Potts, University of Tasmania, “Eucalyptus sits at a pivotal position in the tree of life at the base where the Eurosids split occurred.” This event is estimated to have happened some 100 million year ago, leading to a completely independent evolutionary trajectory from poplar and Arabidopsis, the Eurosids that have been sequenced to date. The Eucalyptus genome would be the first representative of the Myrtales order of flowering plants contributed to the public databases.

The project will be coordinated and the information disseminated by the Eucalyptus Genome Network, EUCAGEN. EUCAGEN was established in 2004 with the aim to promote the generation of public resources for Eucalyptus genomic research. More than 130 scientists from 18 countries are currently involved in EUCAGEN. This number is expected to grow as the Eucalyptus genome sequence, and the genomic research tools that will result from it, becomes a reality.

The South African project leader of this ambitious effort, Alexander Myburg, is a key contributor to the African Centre for Gene Technologies (ACGT), a joint initiative of the University of Pretoria, CSIR and University of the Witwatersrand. “We are very excited to be embarking on this initiative, and proud of the leading role of Prof Myburg and the University of Pretoria”, said Jane Morris, director of the ACGT.