Spotted gum, complete

A second complete eucalypt genome has been assembled and publicly released following a decade-long project involving 22 scientists from Australia, the US and Brazil.

The genome of the spotted gum Corymbia citriodora subsp. variegata will be the reference genome for the genus Corymbia, known as the bloodwoods.

The first complete eucalypt reference genome – published in 2014 for genus Eucalyptus – sequenced Eucalyptus grandis, the flooded gum, which alongside the blue gum (Eucalyptus globulus) is among the world’s most widely planted hardwood forest trees.

The Corymbia reference genome, published yesterday in the journal Communications Biology, is hosted alongside the Eucalyptus reference genome by the US Department of Energy Joint Genome Institute for access by scientists worldwide.

Project scientist Associate Professor David Lee, from University of the Sunshine Coast’s Forest Research Institute, points out that there are about 100 species of Corymbia, primarily in northern and eastern Australia, which represent the closest lineage to genus Eucalyptus, which comprises over 750 species distributed nationwide.

“The species chosen for sequencing grows naturally along the north-east coast of Australia and is grown in plantations in Queensland, northern New South Wales and other countries such as China, Brazil and South Africa,” says Lee.

“This reference genome will be invaluable for future gene discovery and help the breeding of bloodwoods for uses including timber and biomass production, carbon sequestration and even essential oil and charcoal production.”

The research project was initiated in Australia and involved researchers from the University of Queensland, Southern Cross University, University of the Sunshine Coast and University of Tasmania.

The major task of refining the genome assembly, however, was completed in the US when the lead scientist, Dr Adam Healey, moved to the HudsonAlpha Institute for Biotechnology, Alabama, after working on the project as part of his PhD at the University of Queensland.

Professor Brad Potts from the University of Tasmania, a long-time eucalypt champion, described achieving a full genome assembly as completing a “mega project”.

“It is one thing to sequence a genome but quite another to stitch the millions of tiny bits of sequence together into chromosomes and reliably position genes – especially when done independent of other genome assemblies to allow comparative studies,” he says.

Corymbia and Eucalyptus are thought to have diverged about 60 million years ago – after the last mass extinction of the world’s plants and animals, including the dinosaurs – when Australia was still linked with Antarctica.