Eucalyptus tapped as the next tree genome to be sequenced

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 maximise its potential in the burgeoning bio energy market and for capturing excess atmospheric carbon.

The scientific effort to characterise the Eucalyptus genome, uniting some two dozen institutions worldwide, is led by Alexander Myburg of the University of Pretoria (South Africa), with co-leaders Dario Grattapaglia, of EMBRAPA and Catholic University of Braslia (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 US Department of Energy Joint Genome Institute (DOE-JGI) Community Sequencing Program (CSP) and the information will be made freely available over the world wide web.

The project will be supported by significant contributions of genomic data and scientific leadership from ArborGen, LLC, a US-based forestry biotechnology company. Arborgen and its New Zealand-based shareholder, Rubicon Limited will provide access to their private collection of more than 240,000 Eucalyptus gene sequences. ArborGen will work to enable transformation of the model E. grandis clone that will be the source of the genomic sequence. Genolyptus, a Brazilian Eucalyptus research network directed by project co-leader Grattapaglia, will donate more than 120,000 gene sequences and genetic mapping resources required to assemble and annotate the final genome sequence.

"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 optimised for biomass production."

The genus Eucalyptus, comprising over 700 different species, includes 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," said Myburg.

"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 Maud Hinchee, chief technical officer of ArborGen. "This effort will help us advance our goals of producing renewable high-value biomass from a smaller environmental footprint." Hinchee 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 US 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 tonnes 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-leader Grattapaglia.

"From a phylogenetic standpoint," said project collaborator René Vaillancourt, 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 years ago, leading to a completely independent evolutionary trajectory from poplar and Arabidopsis, the Eurosids that have been sequenced to date.